GNU Linux-libre 6.8.7-gnu

[releases.git] / tools / lib / bpf / btf_dump.c

// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)

/*
 * BTF-to-C type converter.
 *
 * Copyright (c) 2019 Facebook
 */

#include <stdbool.h>
#include <stddef.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <endian.h>
#include <errno.h>
#include <limits.h>
#include <linux/err.h>
#include <linux/btf.h>
#include <linux/kernel.h>
#include "btf.h"
#include "hashmap.h"
#include "libbpf.h"
#include "libbpf_internal.h"

static const char PREFIXES[] = "\t\t\t\t\t\t\t\t\t\t\t\t\t";
static const size_t PREFIX_CNT = sizeof(PREFIXES) - 1;

static const char *pfx(int lvl)
{
        return lvl >= PREFIX_CNT ? PREFIXES : &PREFIXES[PREFIX_CNT - lvl];
}

enum btf_dump_type_order_state {
        NOT_ORDERED,
        ORDERING,
        ORDERED,
};

enum btf_dump_type_emit_state {
        NOT_EMITTED,
        EMITTING,
        EMITTED,
};

/* per-type auxiliary state */
struct btf_dump_type_aux_state {
        /* topological sorting state */
        enum btf_dump_type_order_state order_state: 2;
        /* emitting state used to determine the need for forward declaration */
        enum btf_dump_type_emit_state emit_state: 2;
        /* whether forward declaration was already emitted */
        __u8 fwd_emitted: 1;
        /* whether unique non-duplicate name was already assigned */
        __u8 name_resolved: 1;
        /* whether type is referenced from any other type */
        __u8 referenced: 1;
};

/* indent string length; one indent string is added for each indent level */
#define BTF_DATA_INDENT_STR_LEN                 32

/*
 * Common internal data for BTF type data dump operations.
 */
struct btf_dump_data {
        const void *data_end;           /* end of valid data to show */
        bool compact;
        bool skip_names;
        bool emit_zeroes;
        __u8 indent_lvl;        /* base indent level */
        char indent_str[BTF_DATA_INDENT_STR_LEN];
        /* below are used during iteration */
        int depth;
        bool is_array_member;
        bool is_array_terminated;
        bool is_array_char;
};

struct btf_dump {
        const struct btf *btf;
        btf_dump_printf_fn_t printf_fn;
        void *cb_ctx;
        int ptr_sz;
        bool strip_mods;
        bool skip_anon_defs;
        int last_id;

        /* per-type auxiliary state */
        struct btf_dump_type_aux_state *type_states;
        size_t type_states_cap;
        /* per-type optional cached unique name, must be freed, if present */
        const char **cached_names;
        size_t cached_names_cap;

        /* topo-sorted list of dependent type definitions */
        __u32 *emit_queue;
        int emit_queue_cap;
        int emit_queue_cnt;

        /*
         * stack of type declarations (e.g., chain of modifiers, arrays,
         * funcs, etc)
         */
        __u32 *decl_stack;
        int decl_stack_cap;
        int decl_stack_cnt;

        /* maps struct/union/enum name to a number of name occurrences */
        struct hashmap *type_names;
        /*
         * maps typedef identifiers and enum value names to a number of such
         * name occurrences
         */
        struct hashmap *ident_names;
        /*
         * data for typed display; allocated if needed.
         */
        struct btf_dump_data *typed_dump;
};

static size_t str_hash_fn(long key, void *ctx)
{
        return str_hash((void *)key);
}

static bool str_equal_fn(long a, long b, void *ctx)
{
        return strcmp((void *)a, (void *)b) == 0;
}

static const char *btf_name_of(const struct btf_dump *d, __u32 name_off)
{
        return btf__name_by_offset(d->btf, name_off);
}

static void btf_dump_printf(const struct btf_dump *d, const char *fmt, ...)
{
        va_list args;

        va_start(args, fmt);
        d->printf_fn(d->cb_ctx, fmt, args);
        va_end(args);
}

static int btf_dump_mark_referenced(struct btf_dump *d);
static int btf_dump_resize(struct btf_dump *d);

struct btf_dump *btf_dump__new(const struct btf *btf,
                               btf_dump_printf_fn_t printf_fn,
                               void *ctx,
                               const struct btf_dump_opts *opts)
{
        struct btf_dump *d;
        int err;

        if (!OPTS_VALID(opts, btf_dump_opts))
                return libbpf_err_ptr(-EINVAL);

        if (!printf_fn)
                return libbpf_err_ptr(-EINVAL);

        d = calloc(1, sizeof(struct btf_dump));
        if (!d)
                return libbpf_err_ptr(-ENOMEM);

        d->btf = btf;
        d->printf_fn = printf_fn;
        d->cb_ctx = ctx;
        d->ptr_sz = btf__pointer_size(btf) ? : sizeof(void *);

        d->type_names = hashmap__new(str_hash_fn, str_equal_fn, NULL);
        if (IS_ERR(d->type_names)) {
                err = PTR_ERR(d->type_names);
                d->type_names = NULL;
                goto err;
        }
        d->ident_names = hashmap__new(str_hash_fn, str_equal_fn, NULL);
        if (IS_ERR(d->ident_names)) {
                err = PTR_ERR(d->ident_names);
                d->ident_names = NULL;
                goto err;
        }

        err = btf_dump_resize(d);
        if (err)
                goto err;

        return d;
err:
        btf_dump__free(d);
        return libbpf_err_ptr(err);
}

static int btf_dump_resize(struct btf_dump *d)
{
        int err, last_id = btf__type_cnt(d->btf) - 1;

        if (last_id <= d->last_id)
                return 0;

        if (libbpf_ensure_mem((void **)&d->type_states, &d->type_states_cap,
                              sizeof(*d->type_states), last_id + 1))
                return -ENOMEM;
        if (libbpf_ensure_mem((void **)&d->cached_names, &d->cached_names_cap,
                              sizeof(*d->cached_names), last_id + 1))
                return -ENOMEM;

        if (d->last_id == 0) {
                /* VOID is special */
                d->type_states[0].order_state = ORDERED;
                d->type_states[0].emit_state = EMITTED;
        }

        /* eagerly determine referenced types for anon enums */
        err = btf_dump_mark_referenced(d);
        if (err)
                return err;

        d->last_id = last_id;
        return 0;
}

static void btf_dump_free_names(struct hashmap *map)
{
        size_t bkt;
        struct hashmap_entry *cur;

        hashmap__for_each_entry(map, cur, bkt)
                free((void *)cur->pkey);

        hashmap__free(map);
}

void btf_dump__free(struct btf_dump *d)
{
        int i;

        if (IS_ERR_OR_NULL(d))
                return;

        free(d->type_states);
        if (d->cached_names) {
                /* any set cached name is owned by us and should be freed */
                for (i = 0; i <= d->last_id; i++) {
                        if (d->cached_names[i])
                                free((void *)d->cached_names[i]);
                }
        }
        free(d->cached_names);
        free(d->emit_queue);
        free(d->decl_stack);
        btf_dump_free_names(d->type_names);
        btf_dump_free_names(d->ident_names);

        free(d);
}

static int btf_dump_order_type(struct btf_dump *d, __u32 id, bool through_ptr);
static void btf_dump_emit_type(struct btf_dump *d, __u32 id, __u32 cont_id);

/*
 * Dump BTF type in a compilable C syntax, including all the necessary
 * dependent types, necessary for compilation. If some of the dependent types
 * were already emitted as part of previous btf_dump__dump_type() invocation
 * for another type, they won't be emitted again. This API allows callers to
 * filter out BTF types according to user-defined criterias and emitted only
 * minimal subset of types, necessary to compile everything. Full struct/union
 * definitions will still be emitted, even if the only usage is through
 * pointer and could be satisfied with just a forward declaration.
 *
 * Dumping is done in two high-level passes:
 *   1. Topologically sort type definitions to satisfy C rules of compilation.
 *   2. Emit type definitions in C syntax.
 *
 * Returns 0 on success; <0, otherwise.
 */
int btf_dump__dump_type(struct btf_dump *d, __u32 id)
{
        int err, i;

        if (id >= btf__type_cnt(d->btf))
                return libbpf_err(-EINVAL);

        err = btf_dump_resize(d);
        if (err)
                return libbpf_err(err);

        d->emit_queue_cnt = 0;
        err = btf_dump_order_type(d, id, false);
        if (err < 0)
                return libbpf_err(err);

        for (i = 0; i < d->emit_queue_cnt; i++)
                btf_dump_emit_type(d, d->emit_queue[i], 0 /*top-level*/);

        return 0;
}

/*
 * Mark all types that are referenced from any other type. This is used to
 * determine top-level anonymous enums that need to be emitted as an
 * independent type declarations.
 * Anonymous enums come in two flavors: either embedded in a struct's field
 * definition, in which case they have to be declared inline as part of field
 * type declaration; or as a top-level anonymous enum, typically used for
 * declaring global constants. It's impossible to distinguish between two
 * without knowning whether given enum type was referenced from other type:
 * top-level anonymous enum won't be referenced by anything, while embedded
 * one will.
 */
static int btf_dump_mark_referenced(struct btf_dump *d)
{
        int i, j, n = btf__type_cnt(d->btf);
        const struct btf_type *t;
        __u16 vlen;

        for (i = d->last_id + 1; i < n; i++) {
                t = btf__type_by_id(d->btf, i);
                vlen = btf_vlen(t);

                switch (btf_kind(t)) {
                case BTF_KIND_INT:
                case BTF_KIND_ENUM:
                case BTF_KIND_ENUM64:
                case BTF_KIND_FWD:
                case BTF_KIND_FLOAT:
                        break;

                case BTF_KIND_VOLATILE:
                case BTF_KIND_CONST:
                case BTF_KIND_RESTRICT:
                case BTF_KIND_PTR:
                case BTF_KIND_TYPEDEF:
                case BTF_KIND_FUNC:
                case BTF_KIND_VAR:
                case BTF_KIND_DECL_TAG:
                case BTF_KIND_TYPE_TAG:
                        d->type_states[t->type].referenced = 1;
                        break;

                case BTF_KIND_ARRAY: {
                        const struct btf_array *a = btf_array(t);

                        d->type_states[a->index_type].referenced = 1;
                        d->type_states[a->type].referenced = 1;
                        break;
                }
                case BTF_KIND_STRUCT:
                case BTF_KIND_UNION: {
                        const struct btf_member *m = btf_members(t);

                        for (j = 0; j < vlen; j++, m++)
                                d->type_states[m->type].referenced = 1;
                        break;
                }
                case BTF_KIND_FUNC_PROTO: {
                        const struct btf_param *p = btf_params(t);

                        for (j = 0; j < vlen; j++, p++)
                                d->type_states[p->type].referenced = 1;
                        break;
                }
                case BTF_KIND_DATASEC: {
                        const struct btf_var_secinfo *v = btf_var_secinfos(t);

                        for (j = 0; j < vlen; j++, v++)
                                d->type_states[v->type].referenced = 1;
                        break;
                }
                default:
                        return -EINVAL;
                }
        }
        return 0;
}

static int btf_dump_add_emit_queue_id(struct btf_dump *d, __u32 id)
{
        __u32 *new_queue;
        size_t new_cap;

        if (d->emit_queue_cnt >= d->emit_queue_cap) {
                new_cap = max(16, d->emit_queue_cap * 3 / 2);
                new_queue = libbpf_reallocarray(d->emit_queue, new_cap, sizeof(new_queue[0]));
                if (!new_queue)
                        return -ENOMEM;
                d->emit_queue = new_queue;
                d->emit_queue_cap = new_cap;
        }

        d->emit_queue[d->emit_queue_cnt++] = id;
        return 0;
}

/*
 * Determine order of emitting dependent types and specified type to satisfy
 * C compilation rules.  This is done through topological sorting with an
 * additional complication which comes from C rules. The main idea for C is
 * that if some type is "embedded" into a struct/union, it's size needs to be
 * known at the time of definition of containing type. E.g., for:
 *
 *      struct A {};
 *      struct B { struct A x; }
 *
 * struct A *HAS* to be defined before struct B, because it's "embedded",
 * i.e., it is part of struct B layout. But in the following case:
 *
 *      struct A;
 *      struct B { struct A *x; }
 *      struct A {};
 *
 * it's enough to just have a forward declaration of struct A at the time of
 * struct B definition, as struct B has a pointer to struct A, so the size of
 * field x is known without knowing struct A size: it's sizeof(void *).
 *
 * Unfortunately, there are some trickier cases we need to handle, e.g.:
 *
 *      struct A {}; // if this was forward-declaration: compilation error
 *      struct B {
 *              struct { // anonymous struct
 *                      struct A y;
 *              } *x;
 *      };
 *
 * In this case, struct B's field x is a pointer, so it's size is known
 * regardless of the size of (anonymous) struct it points to. But because this
 * struct is anonymous and thus defined inline inside struct B, *and* it
 * embeds struct A, compiler requires full definition of struct A to be known
 * before struct B can be defined. This creates a transitive dependency
 * between struct A and struct B. If struct A was forward-declared before
 * struct B definition and fully defined after struct B definition, that would
 * trigger compilation error.
 *
 * All this means that while we are doing topological sorting on BTF type
 * graph, we need to determine relationships between different types (graph
 * nodes):
 *   - weak link (relationship) between X and Y, if Y *CAN* be
 *   forward-declared at the point of X definition;
 *   - strong link, if Y *HAS* to be fully-defined before X can be defined.
 *
 * The rule is as follows. Given a chain of BTF types from X to Y, if there is
 * BTF_KIND_PTR type in the chain and at least one non-anonymous type
 * Z (excluding X, including Y), then link is weak. Otherwise, it's strong.
 * Weak/strong relationship is determined recursively during DFS traversal and
 * is returned as a result from btf_dump_order_type().
 *
 * btf_dump_order_type() is trying to avoid unnecessary forward declarations,
 * but it is not guaranteeing that no extraneous forward declarations will be
 * emitted.
 *
 * To avoid extra work, algorithm marks some of BTF types as ORDERED, when
 * it's done with them, but not for all (e.g., VOLATILE, CONST, RESTRICT,
 * ARRAY, FUNC_PROTO), as weak/strong semantics for those depends on the
 * entire graph path, so depending where from one came to that BTF type, it
 * might cause weak or strong ordering. For types like STRUCT/UNION/INT/ENUM,
 * once they are processed, there is no need to do it again, so they are
 * marked as ORDERED. We can mark PTR as ORDERED as well, as it semi-forces
 * weak link, unless subsequent referenced STRUCT/UNION/ENUM is anonymous. But
 * in any case, once those are processed, no need to do it again, as the
 * result won't change.
 *
 * Returns:
 *   - 1, if type is part of strong link (so there is strong topological
 *   ordering requirements);
 *   - 0, if type is part of weak link (so can be satisfied through forward
 *   declaration);
 *   - <0, on error (e.g., unsatisfiable type loop detected).
 */
static int btf_dump_order_type(struct btf_dump *d, __u32 id, bool through_ptr)
{
        /*
         * Order state is used to detect strong link cycles, but only for BTF
         * kinds that are or could be an independent definition (i.e.,
         * stand-alone fwd decl, enum, typedef, struct, union). Ptrs, arrays,
         * func_protos, modifiers are just means to get to these definitions.
         * Int/void don't need definitions, they are assumed to be always
         * properly defined.  We also ignore datasec, var, and funcs for now.
         * So for all non-defining kinds, we never even set ordering state,
         * for defining kinds we set ORDERING and subsequently ORDERED if it
         * forms a strong link.
         */
        struct btf_dump_type_aux_state *tstate = &d->type_states[id];
        const struct btf_type *t;
        __u16 vlen;
        int err, i;

        /* return true, letting typedefs know that it's ok to be emitted */
        if (tstate->order_state == ORDERED)
                return 1;

        t = btf__type_by_id(d->btf, id);

        if (tstate->order_state == ORDERING) {
                /* type loop, but resolvable through fwd declaration */
                if (btf_is_composite(t) && through_ptr && t->name_off != 0)
                        return 0;
                pr_warn("unsatisfiable type cycle, id:[%u]\n", id);
                return -ELOOP;
        }

        switch (btf_kind(t)) {
        case BTF_KIND_INT:
        case BTF_KIND_FLOAT:
                tstate->order_state = ORDERED;
                return 0;

        case BTF_KIND_PTR:
                err = btf_dump_order_type(d, t->type, true);
                tstate->order_state = ORDERED;
                return err;

        case BTF_KIND_ARRAY:
                return btf_dump_order_type(d, btf_array(t)->type, false);

        case BTF_KIND_STRUCT:
        case BTF_KIND_UNION: {
                const struct btf_member *m = btf_members(t);
                /*
                 * struct/union is part of strong link, only if it's embedded
                 * (so no ptr in a path) or it's anonymous (so has to be
                 * defined inline, even if declared through ptr)
                 */
                if (through_ptr && t->name_off != 0)
                        return 0;

                tstate->order_state = ORDERING;

                vlen = btf_vlen(t);
                for (i = 0; i < vlen; i++, m++) {
                        err = btf_dump_order_type(d, m->type, false);
                        if (err < 0)
                                return err;
                }

                if (t->name_off != 0) {
                        err = btf_dump_add_emit_queue_id(d, id);
                        if (err < 0)
                                return err;
                }

                tstate->order_state = ORDERED;
                return 1;
        }
        case BTF_KIND_ENUM:
        case BTF_KIND_ENUM64:
        case BTF_KIND_FWD:
                /*
                 * non-anonymous or non-referenced enums are top-level
                 * declarations and should be emitted. Same logic can be
                 * applied to FWDs, it won't hurt anyways.
                 */
                if (t->name_off != 0 || !tstate->referenced) {
                        err = btf_dump_add_emit_queue_id(d, id);
                        if (err)
                                return err;
                }
                tstate->order_state = ORDERED;
                return 1;

        case BTF_KIND_TYPEDEF: {
                int is_strong;

                is_strong = btf_dump_order_type(d, t->type, through_ptr);
                if (is_strong < 0)
                        return is_strong;

                /* typedef is similar to struct/union w.r.t. fwd-decls */
                if (through_ptr && !is_strong)
                        return 0;

                /* typedef is always a named definition */
                err = btf_dump_add_emit_queue_id(d, id);
                if (err)
                        return err;

                d->type_states[id].order_state = ORDERED;
                return 1;
        }
        case BTF_KIND_VOLATILE:
        case BTF_KIND_CONST:
        case BTF_KIND_RESTRICT:
        case BTF_KIND_TYPE_TAG:
                return btf_dump_order_type(d, t->type, through_ptr);

        case BTF_KIND_FUNC_PROTO: {
                const struct btf_param *p = btf_params(t);
                bool is_strong;

                err = btf_dump_order_type(d, t->type, through_ptr);
                if (err < 0)
                        return err;
                is_strong = err > 0;

                vlen = btf_vlen(t);
                for (i = 0; i < vlen; i++, p++) {
                        err = btf_dump_order_type(d, p->type, through_ptr);
                        if (err < 0)
                                return err;
                        if (err > 0)
                                is_strong = true;
                }
                return is_strong;
        }
        case BTF_KIND_FUNC:
        case BTF_KIND_VAR:
        case BTF_KIND_DATASEC:
        case BTF_KIND_DECL_TAG:
                d->type_states[id].order_state = ORDERED;
                return 0;

        default:
                return -EINVAL;
        }
}

static void btf_dump_emit_missing_aliases(struct btf_dump *d, __u32 id,
                                          const struct btf_type *t);

static void btf_dump_emit_struct_fwd(struct btf_dump *d, __u32 id,
                                     const struct btf_type *t);
static void btf_dump_emit_struct_def(struct btf_dump *d, __u32 id,
                                     const struct btf_type *t, int lvl);

static void btf_dump_emit_enum_fwd(struct btf_dump *d, __u32 id,
                                   const struct btf_type *t);
static void btf_dump_emit_enum_def(struct btf_dump *d, __u32 id,
                                   const struct btf_type *t, int lvl);

static void btf_dump_emit_fwd_def(struct btf_dump *d, __u32 id,
                                  const struct btf_type *t);

static void btf_dump_emit_typedef_def(struct btf_dump *d, __u32 id,
                                      const struct btf_type *t, int lvl);

/* a local view into a shared stack */
struct id_stack {
        const __u32 *ids;
        int cnt;
};

static void btf_dump_emit_type_decl(struct btf_dump *d, __u32 id,
                                    const char *fname, int lvl);
static void btf_dump_emit_type_chain(struct btf_dump *d,
                                     struct id_stack *decl_stack,
                                     const char *fname, int lvl);

static const char *btf_dump_type_name(struct btf_dump *d, __u32 id);
static const char *btf_dump_ident_name(struct btf_dump *d, __u32 id);
static size_t btf_dump_name_dups(struct btf_dump *d, struct hashmap *name_map,
                                 const char *orig_name);

static bool btf_dump_is_blacklisted(struct btf_dump *d, __u32 id)
{
        const struct btf_type *t = btf__type_by_id(d->btf, id);

        /* __builtin_va_list is a compiler built-in, which causes compilation
         * errors, when compiling w/ different compiler, then used to compile
         * original code (e.g., GCC to compile kernel, Clang to use generated
         * C header from BTF). As it is built-in, it should be already defined
         * properly internally in compiler.
         */
        if (t->name_off == 0)
                return false;
        return strcmp(btf_name_of(d, t->name_off), "__builtin_va_list") == 0;
}

/*
 * Emit C-syntax definitions of types from chains of BTF types.
 *
 * High-level handling of determining necessary forward declarations are handled
 * by btf_dump_emit_type() itself, but all nitty-gritty details of emitting type
 * declarations/definitions in C syntax  are handled by a combo of
 * btf_dump_emit_type_decl()/btf_dump_emit_type_chain() w/ delegation to
 * corresponding btf_dump_emit_*_{def,fwd}() functions.
 *
 * We also keep track of "containing struct/union type ID" to determine when
 * we reference it from inside and thus can avoid emitting unnecessary forward
 * declaration.
 *
 * This algorithm is designed in such a way, that even if some error occurs
 * (either technical, e.g., out of memory, or logical, i.e., malformed BTF
 * that doesn't comply to C rules completely), algorithm will try to proceed
 * and produce as much meaningful output as possible.
 */
static void btf_dump_emit_type(struct btf_dump *d, __u32 id, __u32 cont_id)
{
        struct btf_dump_type_aux_state *tstate = &d->type_states[id];
        bool top_level_def = cont_id == 0;
        const struct btf_type *t;
        __u16 kind;

        if (tstate->emit_state == EMITTED)
                return;

        t = btf__type_by_id(d->btf, id);
        kind = btf_kind(t);

        if (tstate->emit_state == EMITTING) {
                if (tstate->fwd_emitted)
                        return;

                switch (kind) {
                case BTF_KIND_STRUCT:
                case BTF_KIND_UNION:
                        /*
                         * if we are referencing a struct/union that we are
                         * part of - then no need for fwd declaration
                         */
                        if (id == cont_id)
                                return;
                        if (t->name_off == 0) {
                                pr_warn("anonymous struct/union loop, id:[%u]\n",
                                        id);
                                return;
                        }
                        btf_dump_emit_struct_fwd(d, id, t);
                        btf_dump_printf(d, ";\n\n");
                        tstate->fwd_emitted = 1;
                        break;
                case BTF_KIND_TYPEDEF:
                        /*
                         * for typedef fwd_emitted means typedef definition
                         * was emitted, but it can be used only for "weak"
                         * references through pointer only, not for embedding
                         */
                        if (!btf_dump_is_blacklisted(d, id)) {
                                btf_dump_emit_typedef_def(d, id, t, 0);
                                btf_dump_printf(d, ";\n\n");
                        }
                        tstate->fwd_emitted = 1;
                        break;
                default:
                        break;
                }

                return;
        }

        switch (kind) {
        case BTF_KIND_INT:
                /* Emit type alias definitions if necessary */
                btf_dump_emit_missing_aliases(d, id, t);

                tstate->emit_state = EMITTED;
                break;
        case BTF_KIND_ENUM:
        case BTF_KIND_ENUM64:
                if (top_level_def) {
                        btf_dump_emit_enum_def(d, id, t, 0);
                        btf_dump_printf(d, ";\n\n");
                }
                tstate->emit_state = EMITTED;
                break;
        case BTF_KIND_PTR:
        case BTF_KIND_VOLATILE:
        case BTF_KIND_CONST:
        case BTF_KIND_RESTRICT:
        case BTF_KIND_TYPE_TAG:
                btf_dump_emit_type(d, t->type, cont_id);
                break;
        case BTF_KIND_ARRAY:
                btf_dump_emit_type(d, btf_array(t)->type, cont_id);
                break;
        case BTF_KIND_FWD:
                btf_dump_emit_fwd_def(d, id, t);
                btf_dump_printf(d, ";\n\n");
                tstate->emit_state = EMITTED;
                break;
        case BTF_KIND_TYPEDEF:
                tstate->emit_state = EMITTING;
                btf_dump_emit_type(d, t->type, id);
                /*
                 * typedef can server as both definition and forward
                 * declaration; at this stage someone depends on
                 * typedef as a forward declaration (refers to it
                 * through pointer), so unless we already did it,
                 * emit typedef as a forward declaration
                 */
                if (!tstate->fwd_emitted && !btf_dump_is_blacklisted(d, id)) {
                        btf_dump_emit_typedef_def(d, id, t, 0);
                        btf_dump_printf(d, ";\n\n");
                }
                tstate->emit_state = EMITTED;
                break;
        case BTF_KIND_STRUCT:
        case BTF_KIND_UNION:
                tstate->emit_state = EMITTING;
                /* if it's a top-level struct/union definition or struct/union
                 * is anonymous, then in C we'll be emitting all fields and
                 * their types (as opposed to just `struct X`), so we need to
                 * make sure that all types, referenced from struct/union
                 * members have necessary forward-declarations, where
                 * applicable
                 */
                if (top_level_def || t->name_off == 0) {
                        const struct btf_member *m = btf_members(t);
                        __u16 vlen = btf_vlen(t);
                        int i, new_cont_id;

                        new_cont_id = t->name_off == 0 ? cont_id : id;
                        for (i = 0; i < vlen; i++, m++)
                                btf_dump_emit_type(d, m->type, new_cont_id);
                } else if (!tstate->fwd_emitted && id != cont_id) {
                        btf_dump_emit_struct_fwd(d, id, t);
                        btf_dump_printf(d, ";\n\n");
                        tstate->fwd_emitted = 1;
                }

                if (top_level_def) {
                        btf_dump_emit_struct_def(d, id, t, 0);
                        btf_dump_printf(d, ";\n\n");
                        tstate->emit_state = EMITTED;
                } else {
                        tstate->emit_state = NOT_EMITTED;
                }
                break;
        case BTF_KIND_FUNC_PROTO: {
                const struct btf_param *p = btf_params(t);
                __u16 n = btf_vlen(t);
                int i;

                btf_dump_emit_type(d, t->type, cont_id);
                for (i = 0; i < n; i++, p++)
                        btf_dump_emit_type(d, p->type, cont_id);

                break;
        }
        default:
                break;
        }
}

static bool btf_is_struct_packed(const struct btf *btf, __u32 id,
                                 const struct btf_type *t)
{
        const struct btf_member *m;
        int max_align = 1, align, i, bit_sz;
        __u16 vlen;

        m = btf_members(t);
        vlen = btf_vlen(t);
        /* all non-bitfield fields have to be naturally aligned */
        for (i = 0; i < vlen; i++, m++) {
                align = btf__align_of(btf, m->type);
                bit_sz = btf_member_bitfield_size(t, i);
                if (align && bit_sz == 0 && m->offset % (8 * align) != 0)
                        return true;
                max_align = max(align, max_align);
        }
        /* size of a non-packed struct has to be a multiple of its alignment */
        if (t->size % max_align != 0)
                return true;
        /*
         * if original struct was marked as packed, but its layout is
         * naturally aligned, we'll detect that it's not packed
         */
        return false;
}

static void btf_dump_emit_bit_padding(const struct btf_dump *d,
                                      int cur_off, int next_off, int next_align,
                                      bool in_bitfield, int lvl)
{
        const struct {
                const char *name;
                int bits;
        } pads[] = {
                {"long", d->ptr_sz * 8}, {"int", 32}, {"short", 16}, {"char", 8}
        };
        int new_off, pad_bits, bits, i;
        const char *pad_type;

        if (cur_off >= next_off)
                return; /* no gap */

        /* For filling out padding we want to take advantage of
         * natural alignment rules to minimize unnecessary explicit
         * padding. First, we find the largest type (among long, int,
         * short, or char) that can be used to force naturally aligned
         * boundary. Once determined, we'll use such type to fill in
         * the remaining padding gap. In some cases we can rely on
         * compiler filling some gaps, but sometimes we need to force
         * alignment to close natural alignment with markers like
         * `long: 0` (this is always the case for bitfields).  Note
         * that even if struct itself has, let's say 4-byte alignment
         * (i.e., it only uses up to int-aligned types), using `long:
         * X;` explicit padding doesn't actually change struct's
         * overall alignment requirements, but compiler does take into
         * account that type's (long, in this example) natural
         * alignment requirements when adding implicit padding. We use
         * this fact heavily and don't worry about ruining correct
         * struct alignment requirement.
         */
        for (i = 0; i < ARRAY_SIZE(pads); i++) {
                pad_bits = pads[i].bits;
                pad_type = pads[i].name;

                new_off = roundup(cur_off, pad_bits);
                if (new_off <= next_off)
                        break;
        }

        if (new_off > cur_off && new_off <= next_off) {
                /* We need explicit `<type>: 0` aligning mark if next
                 * field is right on alignment offset and its
                 * alignment requirement is less strict than <type>'s
                 * alignment (so compiler won't naturally align to the
                 * offset we expect), or if subsequent `<type>: X`,
                 * will actually completely fit in the remaining hole,
                 * making compiler basically ignore `<type>: X`
                 * completely.
                 */
                if (in_bitfield ||
                    (new_off == next_off && roundup(cur_off, next_align * 8) != new_off) ||
                    (new_off != next_off && next_off - new_off <= new_off - cur_off))
                        /* but for bitfields we'll emit explicit bit count */
                        btf_dump_printf(d, "\n%s%s: %d;", pfx(lvl), pad_type,
                                        in_bitfield ? new_off - cur_off : 0);
                cur_off = new_off;
        }

        /* Now we know we start at naturally aligned offset for a chosen
         * padding type (long, int, short, or char), and so the rest is just
         * a straightforward filling of remaining padding gap with full
         * `<type>: sizeof(<type>);` markers, except for the last one, which
         * might need smaller than sizeof(<type>) padding.
         */
        while (cur_off != next_off) {
                bits = min(next_off - cur_off, pad_bits);
                if (bits == pad_bits) {
                        btf_dump_printf(d, "\n%s%s: %d;", pfx(lvl), pad_type, pad_bits);
                        cur_off += bits;
                        continue;
                }
                /* For the remainder padding that doesn't cover entire
                 * pad_type bit length, we pick the smallest necessary type.
                 * This is pure aesthetics, we could have just used `long`,
                 * but having smallest necessary one communicates better the
                 * scale of the padding gap.
                 */
                for (i = ARRAY_SIZE(pads) - 1; i >= 0; i--) {
                        pad_type = pads[i].name;
                        pad_bits = pads[i].bits;
                        if (pad_bits < bits)
                                continue;

                        btf_dump_printf(d, "\n%s%s: %d;", pfx(lvl), pad_type, bits);
                        cur_off += bits;
                        break;
                }
        }
}

static void btf_dump_emit_struct_fwd(struct btf_dump *d, __u32 id,
                                     const struct btf_type *t)
{
        btf_dump_printf(d, "%s%s%s",
                        btf_is_struct(t) ? "struct" : "union",
                        t->name_off ? " " : "",
                        btf_dump_type_name(d, id));
}

static void btf_dump_emit_struct_def(struct btf_dump *d,
                                     __u32 id,
                                     const struct btf_type *t,
                                     int lvl)
{
        const struct btf_member *m = btf_members(t);
        bool is_struct = btf_is_struct(t);
        bool packed, prev_bitfield = false;
        int align, i, off = 0;
        __u16 vlen = btf_vlen(t);

        align = btf__align_of(d->btf, id);
        packed = is_struct ? btf_is_struct_packed(d->btf, id, t) : 0;

        btf_dump_printf(d, "%s%s%s {",
                        is_struct ? "struct" : "union",
                        t->name_off ? " " : "",
                        btf_dump_type_name(d, id));

        for (i = 0; i < vlen; i++, m++) {
                const char *fname;
                int m_off, m_sz, m_align;
                bool in_bitfield;

                fname = btf_name_of(d, m->name_off);
                m_sz = btf_member_bitfield_size(t, i);
                m_off = btf_member_bit_offset(t, i);
                m_align = packed ? 1 : btf__align_of(d->btf, m->type);

                in_bitfield = prev_bitfield && m_sz != 0;

                btf_dump_emit_bit_padding(d, off, m_off, m_align, in_bitfield, lvl + 1);
                btf_dump_printf(d, "\n%s", pfx(lvl + 1));
                btf_dump_emit_type_decl(d, m->type, fname, lvl + 1);

                if (m_sz) {
                        btf_dump_printf(d, ": %d", m_sz);
                        off = m_off + m_sz;
                        prev_bitfield = true;
                } else {
                        m_sz = max((__s64)0, btf__resolve_size(d->btf, m->type));
                        off = m_off + m_sz * 8;
                        prev_bitfield = false;
                }

                btf_dump_printf(d, ";");
        }

        /* pad at the end, if necessary */
        if (is_struct)
                btf_dump_emit_bit_padding(d, off, t->size * 8, align, false, lvl + 1);

        /*
         * Keep `struct empty {}` on a single line,
         * only print newline when there are regular or padding fields.
         */
        if (vlen || t->size) {
                btf_dump_printf(d, "\n");
                btf_dump_printf(d, "%s}", pfx(lvl));
        } else {
                btf_dump_printf(d, "}");
        }
        if (packed)
                btf_dump_printf(d, " __attribute__((packed))");
}

static const char *missing_base_types[][2] = {
        /*
         * GCC emits typedefs to its internal __PolyX_t types when compiling Arm
         * SIMD intrinsics. Alias them to standard base types.
         */
        { "__Poly8_t",          "unsigned char" },
        { "__Poly16_t",         "unsigned short" },
        { "__Poly64_t",         "unsigned long long" },
        { "__Poly128_t",        "unsigned __int128" },
};

static void btf_dump_emit_missing_aliases(struct btf_dump *d, __u32 id,
                                          const struct btf_type *t)
{
        const char *name = btf_dump_type_name(d, id);
        int i;

        for (i = 0; i < ARRAY_SIZE(missing_base_types); i++) {
                if (strcmp(name, missing_base_types[i][0]) == 0) {
                        btf_dump_printf(d, "typedef %s %s;\n\n",
                                        missing_base_types[i][1], name);
                        break;
                }
        }
}

static void btf_dump_emit_enum_fwd(struct btf_dump *d, __u32 id,
                                   const struct btf_type *t)
{
        btf_dump_printf(d, "enum %s", btf_dump_type_name(d, id));
}

static void btf_dump_emit_enum32_val(struct btf_dump *d,
                                     const struct btf_type *t,
                                     int lvl, __u16 vlen)
{
        const struct btf_enum *v = btf_enum(t);
        bool is_signed = btf_kflag(t);
        const char *fmt_str;
        const char *name;
        size_t dup_cnt;
        int i;

        for (i = 0; i < vlen; i++, v++) {
                name = btf_name_of(d, v->name_off);
                /* enumerators share namespace with typedef idents */
                dup_cnt = btf_dump_name_dups(d, d->ident_names, name);
                if (dup_cnt > 1) {
                        fmt_str = is_signed ? "\n%s%s___%zd = %d," : "\n%s%s___%zd = %u,";
                        btf_dump_printf(d, fmt_str, pfx(lvl + 1), name, dup_cnt, v->val);
                } else {
                        fmt_str = is_signed ? "\n%s%s = %d," : "\n%s%s = %u,";
                        btf_dump_printf(d, fmt_str, pfx(lvl + 1), name, v->val);
                }
        }
}

static void btf_dump_emit_enum64_val(struct btf_dump *d,
                                     const struct btf_type *t,
                                     int lvl, __u16 vlen)
{
        const struct btf_enum64 *v = btf_enum64(t);
        bool is_signed = btf_kflag(t);
        const char *fmt_str;
        const char *name;
        size_t dup_cnt;
        __u64 val;
        int i;

        for (i = 0; i < vlen; i++, v++) {
                name = btf_name_of(d, v->name_off);
                dup_cnt = btf_dump_name_dups(d, d->ident_names, name);
                val = btf_enum64_value(v);
                if (dup_cnt > 1) {
                        fmt_str = is_signed ? "\n%s%s___%zd = %lldLL,"
                                            : "\n%s%s___%zd = %lluULL,";
                        btf_dump_printf(d, fmt_str,
                                        pfx(lvl + 1), name, dup_cnt,
                                        (unsigned long long)val);
                } else {
                        fmt_str = is_signed ? "\n%s%s = %lldLL,"
                                            : "\n%s%s = %lluULL,";
                        btf_dump_printf(d, fmt_str,
                                        pfx(lvl + 1), name,
                                        (unsigned long long)val);
                }
        }
}
static void btf_dump_emit_enum_def(struct btf_dump *d, __u32 id,
                                   const struct btf_type *t,
                                   int lvl)
{
        __u16 vlen = btf_vlen(t);

        btf_dump_printf(d, "enum%s%s",
                        t->name_off ? " " : "",
                        btf_dump_type_name(d, id));

        if (!vlen)
                return;

        btf_dump_printf(d, " {");
        if (btf_is_enum(t))
                btf_dump_emit_enum32_val(d, t, lvl, vlen);
        else
                btf_dump_emit_enum64_val(d, t, lvl, vlen);
        btf_dump_printf(d, "\n%s}", pfx(lvl));

        /* special case enums with special sizes */
        if (t->size == 1) {
                /* one-byte enums can be forced with mode(byte) attribute */
                btf_dump_printf(d, " __attribute__((mode(byte)))");
        } else if (t->size == 8 && d->ptr_sz == 8) {
                /* enum can be 8-byte sized if one of the enumerator values
                 * doesn't fit in 32-bit integer, or by adding mode(word)
                 * attribute (but probably only on 64-bit architectures); do
                 * our best here to try to satisfy the contract without adding
                 * unnecessary attributes
                 */
                bool needs_word_mode;

                if (btf_is_enum(t)) {
                        /* enum can't represent 64-bit values, so we need word mode */
                        needs_word_mode = true;
                } else {
                        /* enum64 needs mode(word) if none of its values has
                         * non-zero upper 32-bits (which means that all values
                         * fit in 32-bit integers and won't cause compiler to
                         * bump enum to be 64-bit naturally
                         */
                        int i;

                        needs_word_mode = true;
                        for (i = 0; i < vlen; i++) {
                                if (btf_enum64(t)[i].val_hi32 != 0) {
                                        needs_word_mode = false;
                                        break;
                                }
                        }
                }
                if (needs_word_mode)
                        btf_dump_printf(d, " __attribute__((mode(word)))");
        }

}

static void btf_dump_emit_fwd_def(struct btf_dump *d, __u32 id,
                                  const struct btf_type *t)
{
        const char *name = btf_dump_type_name(d, id);

        if (btf_kflag(t))
                btf_dump_printf(d, "union %s", name);
        else
                btf_dump_printf(d, "struct %s", name);
}

static void btf_dump_emit_typedef_def(struct btf_dump *d, __u32 id,
                                     const struct btf_type *t, int lvl)
{
        const char *name = btf_dump_ident_name(d, id);

        /*
         * Old GCC versions are emitting invalid typedef for __gnuc_va_list
         * pointing to VOID. This generates warnings from btf_dump() and
         * results in uncompilable header file, so we are fixing it up here
         * with valid typedef into __builtin_va_list.
         */
        if (t->type == 0 && strcmp(name, "__gnuc_va_list") == 0) {
                btf_dump_printf(d, "typedef __builtin_va_list __gnuc_va_list");
                return;
        }

        btf_dump_printf(d, "typedef ");
        btf_dump_emit_type_decl(d, t->type, name, lvl);
}

static int btf_dump_push_decl_stack_id(struct btf_dump *d, __u32 id)
{
        __u32 *new_stack;
        size_t new_cap;

        if (d->decl_stack_cnt >= d->decl_stack_cap) {
                new_cap = max(16, d->decl_stack_cap * 3 / 2);
                new_stack = libbpf_reallocarray(d->decl_stack, new_cap, sizeof(new_stack[0]));
                if (!new_stack)
                        return -ENOMEM;
                d->decl_stack = new_stack;
                d->decl_stack_cap = new_cap;
        }

        d->decl_stack[d->decl_stack_cnt++] = id;

        return 0;
}

/*
 * Emit type declaration (e.g., field type declaration in a struct or argument
 * declaration in function prototype) in correct C syntax.
 *
 * For most types it's trivial, but there are few quirky type declaration
 * cases worth mentioning:
 *   - function prototypes (especially nesting of function prototypes);
 *   - arrays;
 *   - const/volatile/restrict for pointers vs other types.
 *
 * For a good discussion of *PARSING* C syntax (as a human), see
 * Peter van der Linden's "Expert C Programming: Deep C Secrets",
 * Ch.3 "Unscrambling Declarations in C".
 *
 * It won't help with BTF to C conversion much, though, as it's an opposite
 * problem. So we came up with this algorithm in reverse to van der Linden's
 * parsing algorithm. It goes from structured BTF representation of type
 * declaration to a valid compilable C syntax.
 *
 * For instance, consider this C typedef:
 *      typedef const int * const * arr[10] arr_t;
 * It will be represented in BTF with this chain of BTF types:
 *      [typedef] -> [array] -> [ptr] -> [const] -> [ptr] -> [const] -> [int]
 *
 * Notice how [const] modifier always goes before type it modifies in BTF type
 * graph, but in C syntax, const/volatile/restrict modifiers are written to
 * the right of pointers, but to the left of other types. There are also other
 * quirks, like function pointers, arrays of them, functions returning other
 * functions, etc.
 *
 * We handle that by pushing all the types to a stack, until we hit "terminal"
 * type (int/enum/struct/union/fwd). Then depending on the kind of a type on
 * top of a stack, modifiers are handled differently. Array/function pointers
 * have also wildly different syntax and how nesting of them are done. See
 * code for authoritative definition.
 *
 * To avoid allocating new stack for each independent chain of BTF types, we
 * share one bigger stack, with each chain working only on its own local view
 * of a stack frame. Some care is required to "pop" stack frames after
 * processing type declaration chain.
 */
int btf_dump__emit_type_decl(struct btf_dump *d, __u32 id,
                             const struct btf_dump_emit_type_decl_opts *opts)
{
        const char *fname;
        int lvl, err;

        if (!OPTS_VALID(opts, btf_dump_emit_type_decl_opts))
                return libbpf_err(-EINVAL);

        err = btf_dump_resize(d);
        if (err)
                return libbpf_err(err);

        fname = OPTS_GET(opts, field_name, "");
        lvl = OPTS_GET(opts, indent_level, 0);
        d->strip_mods = OPTS_GET(opts, strip_mods, false);
        btf_dump_emit_type_decl(d, id, fname, lvl);
        d->strip_mods = false;
        return 0;
}

static void btf_dump_emit_type_decl(struct btf_dump *d, __u32 id,
                                    const char *fname, int lvl)
{
        struct id_stack decl_stack;
        const struct btf_type *t;
        int err, stack_start;

        stack_start = d->decl_stack_cnt;
        for (;;) {
                t = btf__type_by_id(d->btf, id);
                if (d->strip_mods && btf_is_mod(t))
                        goto skip_mod;

                err = btf_dump_push_decl_stack_id(d, id);
                if (err < 0) {
                        /*
                         * if we don't have enough memory for entire type decl
                         * chain, restore stack, emit warning, and try to
                         * proceed nevertheless
                         */
                        pr_warn("not enough memory for decl stack:%d", err);
                        d->decl_stack_cnt = stack_start;
                        return;
                }
skip_mod:
                /* VOID */
                if (id == 0)
                        break;

                switch (btf_kind(t)) {
                case BTF_KIND_PTR:
                case BTF_KIND_VOLATILE:
                case BTF_KIND_CONST:
                case BTF_KIND_RESTRICT:
                case BTF_KIND_FUNC_PROTO:
                case BTF_KIND_TYPE_TAG:
                        id = t->type;
                        break;
                case BTF_KIND_ARRAY:
                        id = btf_array(t)->type;
                        break;
                case BTF_KIND_INT:
                case BTF_KIND_ENUM:
                case BTF_KIND_ENUM64:
                case BTF_KIND_FWD:
                case BTF_KIND_STRUCT:
                case BTF_KIND_UNION:
                case BTF_KIND_TYPEDEF:
                case BTF_KIND_FLOAT:
                        goto done;
                default:
                        pr_warn("unexpected type in decl chain, kind:%u, id:[%u]\n",
                                btf_kind(t), id);
                        goto done;
                }
        }
done:
        /*
         * We might be inside a chain of declarations (e.g., array of function
         * pointers returning anonymous (so inlined) structs, having another
         * array field). Each of those needs its own "stack frame" to handle
         * emitting of declarations. Those stack frames are non-overlapping
         * portions of shared btf_dump->decl_stack. To make it a bit nicer to
         * handle this set of nested stacks, we create a view corresponding to
         * our own "stack frame" and work with it as an independent stack.
         * We'll need to clean up after emit_type_chain() returns, though.
         */
        decl_stack.ids = d->decl_stack + stack_start;
        decl_stack.cnt = d->decl_stack_cnt - stack_start;
        btf_dump_emit_type_chain(d, &decl_stack, fname, lvl);
        /*
         * emit_type_chain() guarantees that it will pop its entire decl_stack
         * frame before returning. But it works with a read-only view into
         * decl_stack, so it doesn't actually pop anything from the
         * perspective of shared btf_dump->decl_stack, per se. We need to
         * reset decl_stack state to how it was before us to avoid it growing
         * all the time.
         */
        d->decl_stack_cnt = stack_start;
}

static void btf_dump_emit_mods(struct btf_dump *d, struct id_stack *decl_stack)
{
        const struct btf_type *t;
        __u32 id;

        while (decl_stack->cnt) {
                id = decl_stack->ids[decl_stack->cnt - 1];
                t = btf__type_by_id(d->btf, id);

                switch (btf_kind(t)) {
                case BTF_KIND_VOLATILE:
                        btf_dump_printf(d, "volatile ");
                        break;
                case BTF_KIND_CONST:
                        btf_dump_printf(d, "const ");
                        break;
                case BTF_KIND_RESTRICT:
                        btf_dump_printf(d, "restrict ");
                        break;
                default:
                        return;
                }
                decl_stack->cnt--;
        }
}

static void btf_dump_drop_mods(struct btf_dump *d, struct id_stack *decl_stack)
{
        const struct btf_type *t;
        __u32 id;

        while (decl_stack->cnt) {
                id = decl_stack->ids[decl_stack->cnt - 1];
                t = btf__type_by_id(d->btf, id);
                if (!btf_is_mod(t))
                        return;
                decl_stack->cnt--;
        }
}

static void btf_dump_emit_name(const struct btf_dump *d,
                               const char *name, bool last_was_ptr)
{
        bool separate = name[0] && !last_was_ptr;

        btf_dump_printf(d, "%s%s", separate ? " " : "", name);
}

static void btf_dump_emit_type_chain(struct btf_dump *d,
                                     struct id_stack *decls,
                                     const char *fname, int lvl)
{
        /*
         * last_was_ptr is used to determine if we need to separate pointer
         * asterisk (*) from previous part of type signature with space, so
         * that we get `int ***`, instead of `int * * *`. We default to true
         * for cases where we have single pointer in a chain. E.g., in ptr ->
         * func_proto case. func_proto will start a new emit_type_chain call
         * with just ptr, which should be emitted as (*) or (*<fname>), so we
         * don't want to prepend space for that last pointer.
         */
        bool last_was_ptr = true;
        const struct btf_type *t;
        const char *name;
        __u16 kind;
        __u32 id;

        while (decls->cnt) {
                id = decls->ids[--decls->cnt];
                if (id == 0) {
                        /* VOID is a special snowflake */
                        btf_dump_emit_mods(d, decls);
                        btf_dump_printf(d, "void");
                        last_was_ptr = false;
                        continue;
                }

                t = btf__type_by_id(d->btf, id);
                kind = btf_kind(t);

                switch (kind) {
                case BTF_KIND_INT:
                case BTF_KIND_FLOAT:
                        btf_dump_emit_mods(d, decls);
                        name = btf_name_of(d, t->name_off);
                        btf_dump_printf(d, "%s", name);
                        break;
                case BTF_KIND_STRUCT:
                case BTF_KIND_UNION:
                        btf_dump_emit_mods(d, decls);
                        /* inline anonymous struct/union */
                        if (t->name_off == 0 && !d->skip_anon_defs)
                                btf_dump_emit_struct_def(d, id, t, lvl);
                        else
                                btf_dump_emit_struct_fwd(d, id, t);
                        break;
                case BTF_KIND_ENUM:
                case BTF_KIND_ENUM64:
                        btf_dump_emit_mods(d, decls);
                        /* inline anonymous enum */
                        if (t->name_off == 0 && !d->skip_anon_defs)
                                btf_dump_emit_enum_def(d, id, t, lvl);
                        else
                                btf_dump_emit_enum_fwd(d, id, t);
                        break;
                case BTF_KIND_FWD:
                        btf_dump_emit_mods(d, decls);
                        btf_dump_emit_fwd_def(d, id, t);
                        break;
                case BTF_KIND_TYPEDEF:
                        btf_dump_emit_mods(d, decls);
                        btf_dump_printf(d, "%s", btf_dump_ident_name(d, id));
                        break;
                case BTF_KIND_PTR:
                        btf_dump_printf(d, "%s", last_was_ptr ? "*" : " *");
                        break;
                case BTF_KIND_VOLATILE:
                        btf_dump_printf(d, " volatile");
                        break;
                case BTF_KIND_CONST:
                        btf_dump_printf(d, " const");
                        break;
                case BTF_KIND_RESTRICT:
                        btf_dump_printf(d, " restrict");
                        break;
                case BTF_KIND_TYPE_TAG:
                        btf_dump_emit_mods(d, decls);
                        name = btf_name_of(d, t->name_off);
                        btf_dump_printf(d, " __attribute__((btf_type_tag(\"%s\")))", name);
                        break;
                case BTF_KIND_ARRAY: {
                        const struct btf_array *a = btf_array(t);
                        const struct btf_type *next_t;
                        __u32 next_id;
                        bool multidim;
                        /*
                         * GCC has a bug
                         * (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=8354)
                         * which causes it to emit extra const/volatile
                         * modifiers for an array, if array's element type has
                         * const/volatile modifiers. Clang doesn't do that.
                         * In general, it doesn't seem very meaningful to have
                         * a const/volatile modifier for array, so we are
                         * going to silently skip them here.
                         */
                        btf_dump_drop_mods(d, decls);

                        if (decls->cnt == 0) {
                                btf_dump_emit_name(d, fname, last_was_ptr);
                                btf_dump_printf(d, "[%u]", a->nelems);
                                return;
                        }

                        next_id = decls->ids[decls->cnt - 1];
                        next_t = btf__type_by_id(d->btf, next_id);
                        multidim = btf_is_array(next_t);
                        /* we need space if we have named non-pointer */
                        if (fname[0] && !last_was_ptr)
                                btf_dump_printf(d, " ");
                        /* no parentheses for multi-dimensional array */
                        if (!multidim)
                                btf_dump_printf(d, "(");
                        btf_dump_emit_type_chain(d, decls, fname, lvl);
                        if (!multidim)
                                btf_dump_printf(d, ")");
                        btf_dump_printf(d, "[%u]", a->nelems);
                        return;
                }
                case BTF_KIND_FUNC_PROTO: {
                        const struct btf_param *p = btf_params(t);
                        __u16 vlen = btf_vlen(t);
                        int i;

                        /*
                         * GCC emits extra volatile qualifier for
                         * __attribute__((noreturn)) function pointers. Clang
                         * doesn't do it. It's a GCC quirk for backwards
                         * compatibility with code written for GCC <2.5. So,
                         * similarly to extra qualifiers for array, just drop
                         * them, instead of handling them.
                         */
                        btf_dump_drop_mods(d, decls);
                        if (decls->cnt) {
                                btf_dump_printf(d, " (");
                                btf_dump_emit_type_chain(d, decls, fname, lvl);
                                btf_dump_printf(d, ")");
                        } else {
                                btf_dump_emit_name(d, fname, last_was_ptr);
                        }
                        btf_dump_printf(d, "(");
                        /*
                         * Clang for BPF target generates func_proto with no
                         * args as a func_proto with a single void arg (e.g.,
                         * `int (*f)(void)` vs just `int (*f)()`). We are
                         * going to pretend there are no args for such case.
                         */
                        if (vlen == 1 && p->type == 0) {
                                btf_dump_printf(d, ")");
                                return;
                        }

                        for (i = 0; i < vlen; i++, p++) {
                                if (i > 0)
                                        btf_dump_printf(d, ", ");

                                /* last arg of type void is vararg */
                                if (i == vlen - 1 && p->type == 0) {
                                        btf_dump_printf(d, "...");
                                        break;
                                }

                                name = btf_name_of(d, p->name_off);
                                btf_dump_emit_type_decl(d, p->type, name, lvl);
                        }

                        btf_dump_printf(d, ")");
                        return;
                }
                default:
                        pr_warn("unexpected type in decl chain, kind:%u, id:[%u]\n",
                                kind, id);
                        return;
                }

                last_was_ptr = kind == BTF_KIND_PTR;
        }

        btf_dump_emit_name(d, fname, last_was_ptr);
}

/* show type name as (type_name) */
static void btf_dump_emit_type_cast(struct btf_dump *d, __u32 id,
                                    bool top_level)
{
        const struct btf_type *t;

        /* for array members, we don't bother emitting type name for each
         * member to avoid the redundancy of
         * .name = (char[4])[(char)'f',(char)'o',(char)'o',]
         */
        if (d->typed_dump->is_array_member)
                return;

        /* avoid type name specification for variable/section; it will be done
         * for the associated variable value(s).
         */
        t = btf__type_by_id(d->btf, id);
        if (btf_is_var(t) || btf_is_datasec(t))
                return;

        if (top_level)
                btf_dump_printf(d, "(");

        d->skip_anon_defs = true;
        d->strip_mods = true;
        btf_dump_emit_type_decl(d, id, "", 0);
        d->strip_mods = false;
        d->skip_anon_defs = false;

        if (top_level)
                btf_dump_printf(d, ")");
}

/* return number of duplicates (occurrences) of a given name */
static size_t btf_dump_name_dups(struct btf_dump *d, struct hashmap *name_map,
                                 const char *orig_name)
{
        char *old_name, *new_name;
        size_t dup_cnt = 0;
        int err;

        new_name = strdup(orig_name);
        if (!new_name)
                return 1;

        (void)hashmap__find(name_map, orig_name, &dup_cnt);
        dup_cnt++;

        err = hashmap__set(name_map, new_name, dup_cnt, &old_name, NULL);
        if (err)
                free(new_name);

        free(old_name);

        return dup_cnt;
}

static const char *btf_dump_resolve_name(struct btf_dump *d, __u32 id,
                                         struct hashmap *name_map)
{
        struct btf_dump_type_aux_state *s = &d->type_states[id];
        const struct btf_type *t = btf__type_by_id(d->btf, id);
        const char *orig_name = btf_name_of(d, t->name_off);
        const char **cached_name = &d->cached_names[id];
        size_t dup_cnt;

        if (t->name_off == 0)
                return "";

        if (s->name_resolved)
                return *cached_name ? *cached_name : orig_name;

        if (btf_is_fwd(t) || (btf_is_enum(t) && btf_vlen(t) == 0)) {
                s->name_resolved = 1;
                return orig_name;
        }

        dup_cnt = btf_dump_name_dups(d, name_map, orig_name);
        if (dup_cnt > 1) {
                const size_t max_len = 256;
                char new_name[max_len];

                snprintf(new_name, max_len, "%s___%zu", orig_name, dup_cnt);
                *cached_name = strdup(new_name);
        }

        s->name_resolved = 1;
        return *cached_name ? *cached_name : orig_name;
}

static const char *btf_dump_type_name(struct btf_dump *d, __u32 id)
{
        return btf_dump_resolve_name(d, id, d->type_names);
}

static const char *btf_dump_ident_name(struct btf_dump *d, __u32 id)
{
        return btf_dump_resolve_name(d, id, d->ident_names);
}

static int btf_dump_dump_type_data(struct btf_dump *d,
                                   const char *fname,
                                   const struct btf_type *t,
                                   __u32 id,
                                   const void *data,
                                   __u8 bits_offset,
                                   __u8 bit_sz);

static const char *btf_dump_data_newline(struct btf_dump *d)
{
        return d->typed_dump->compact || d->typed_dump->depth == 0 ? "" : "\n";
}

static const char *btf_dump_data_delim(struct btf_dump *d)
{
        return d->typed_dump->depth == 0 ? "" : ",";
}

static void btf_dump_data_pfx(struct btf_dump *d)
{
        int i, lvl = d->typed_dump->indent_lvl + d->typed_dump->depth;

        if (d->typed_dump->compact)
                return;

        for (i = 0; i < lvl; i++)
                btf_dump_printf(d, "%s", d->typed_dump->indent_str);
}

/* A macro is used here as btf_type_value[s]() appends format specifiers
 * to the format specifier passed in; these do the work of appending
 * delimiters etc while the caller simply has to specify the type values
 * in the format specifier + value(s).
 */
#define btf_dump_type_values(d, fmt, ...)                               \
        btf_dump_printf(d, fmt "%s%s",                                  \
                        ##__VA_ARGS__,                                  \
                        btf_dump_data_delim(d),                         \
                        btf_dump_data_newline(d))

static int btf_dump_unsupported_data(struct btf_dump *d,
                                     const struct btf_type *t,
                                     __u32 id)
{
        btf_dump_printf(d, "<unsupported kind:%u>", btf_kind(t));
        return -ENOTSUP;
}

static int btf_dump_get_bitfield_value(struct btf_dump *d,
                                       const struct btf_type *t,
                                       const void *data,
                                       __u8 bits_offset,
                                       __u8 bit_sz,
                                       __u64 *value)
{
        __u16 left_shift_bits, right_shift_bits;
        const __u8 *bytes = data;
        __u8 nr_copy_bits;
        __u64 num = 0;
        int i;

        /* Maximum supported bitfield size is 64 bits */
        if (t->size > 8) {
                pr_warn("unexpected bitfield size %d\n", t->size);
                return -EINVAL;
        }

        /* Bitfield value retrieval is done in two steps; first relevant bytes are
         * stored in num, then we left/right shift num to eliminate irrelevant bits.
         */
#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
        for (i = t->size - 1; i >= 0; i--)
                num = num * 256 + bytes[i];
        nr_copy_bits = bit_sz + bits_offset;
#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
        for (i = 0; i < t->size; i++)
                num = num * 256 + bytes[i];
        nr_copy_bits = t->size * 8 - bits_offset;
#else
# error "Unrecognized __BYTE_ORDER__"
#endif
        left_shift_bits = 64 - nr_copy_bits;
        right_shift_bits = 64 - bit_sz;

        *value = (num << left_shift_bits) >> right_shift_bits;

        return 0;
}

static int btf_dump_bitfield_check_zero(struct btf_dump *d,
                                        const struct btf_type *t,
                                        const void *data,
                                        __u8 bits_offset,
                                        __u8 bit_sz)
{
        __u64 check_num;
        int err;

        err = btf_dump_get_bitfield_value(d, t, data, bits_offset, bit_sz, &check_num);
        if (err)
                return err;
        if (check_num == 0)
                return -ENODATA;
        return 0;
}

static int btf_dump_bitfield_data(struct btf_dump *d,
                                  const struct btf_type *t,
                                  const void *data,
                                  __u8 bits_offset,
                                  __u8 bit_sz)
{
        __u64 print_num;
        int err;

        err = btf_dump_get_bitfield_value(d, t, data, bits_offset, bit_sz, &print_num);
        if (err)
                return err;

        btf_dump_type_values(d, "0x%llx", (unsigned long long)print_num);

        return 0;
}

/* ints, floats and ptrs */
static int btf_dump_base_type_check_zero(struct btf_dump *d,
                                         const struct btf_type *t,
                                         __u32 id,
                                         const void *data)
{
        static __u8 bytecmp[16] = {};
        int nr_bytes;

        /* For pointer types, pointer size is not defined on a per-type basis.
         * On dump creation however, we store the pointer size.
         */
        if (btf_kind(t) == BTF_KIND_PTR)
                nr_bytes = d->ptr_sz;
        else
                nr_bytes = t->size;

        if (nr_bytes < 1 || nr_bytes > 16) {
                pr_warn("unexpected size %d for id [%u]\n", nr_bytes, id);
                return -EINVAL;
        }

        if (memcmp(data, bytecmp, nr_bytes) == 0)
                return -ENODATA;
        return 0;
}

static bool ptr_is_aligned(const struct btf *btf, __u32 type_id,
                           const void *data)
{
        int alignment = btf__align_of(btf, type_id);

        if (alignment == 0)
                return false;

        return ((uintptr_t)data) % alignment == 0;
}

static int btf_dump_int_data(struct btf_dump *d,
                             const struct btf_type *t,
                             __u32 type_id,
                             const void *data,
                             __u8 bits_offset)
{
        __u8 encoding = btf_int_encoding(t);
        bool sign = encoding & BTF_INT_SIGNED;
        char buf[16] __attribute__((aligned(16)));
        int sz = t->size;

        if (sz == 0 || sz > sizeof(buf)) {
                pr_warn("unexpected size %d for id [%u]\n", sz, type_id);
                return -EINVAL;
        }

        /* handle packed int data - accesses of integers not aligned on
         * int boundaries can cause problems on some platforms.
         */
        if (!ptr_is_aligned(d->btf, type_id, data)) {
                memcpy(buf, data, sz);
                data = buf;
        }

        switch (sz) {
        case 16: {
                const __u64 *ints = data;
                __u64 lsi, msi;

                /* avoid use of __int128 as some 32-bit platforms do not
                 * support it.
                 */
#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
                lsi = ints[0];
                msi = ints[1];
#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
                lsi = ints[1];
                msi = ints[0];
#else
# error "Unrecognized __BYTE_ORDER__"
#endif
                if (msi == 0)
                        btf_dump_type_values(d, "0x%llx", (unsigned long long)lsi);
                else
                        btf_dump_type_values(d, "0x%llx%016llx", (unsigned long long)msi,
                                             (unsigned long long)lsi);
                break;
        }
        case 8:
                if (sign)
                        btf_dump_type_values(d, "%lld", *(long long *)data);
                else
                        btf_dump_type_values(d, "%llu", *(unsigned long long *)data);
                break;
        case 4:
                if (sign)
                        btf_dump_type_values(d, "%d", *(__s32 *)data);
                else
                        btf_dump_type_values(d, "%u", *(__u32 *)data);
                break;
        case 2:
                if (sign)
                        btf_dump_type_values(d, "%d", *(__s16 *)data);
                else
                        btf_dump_type_values(d, "%u", *(__u16 *)data);
                break;
        case 1:
                if (d->typed_dump->is_array_char) {
                        /* check for null terminator */
                        if (d->typed_dump->is_array_terminated)
                                break;
                        if (*(char *)data == '\0') {
                                d->typed_dump->is_array_terminated = true;
                                break;
                        }
                        if (isprint(*(char *)data)) {
                                btf_dump_type_values(d, "'%c'", *(char *)data);
                                break;
                        }
                }
                if (sign)
                        btf_dump_type_values(d, "%d", *(__s8 *)data);
                else
                        btf_dump_type_values(d, "%u", *(__u8 *)data);
                break;
        default:
                pr_warn("unexpected sz %d for id [%u]\n", sz, type_id);
                return -EINVAL;
        }
        return 0;
}

union float_data {
        long double ld;
        double d;
        float f;
};

static int btf_dump_float_data(struct btf_dump *d,
                               const struct btf_type *t,
                               __u32 type_id,
                               const void *data)
{
        const union float_data *flp = data;
        union float_data fl;
        int sz = t->size;

        /* handle unaligned data; copy to local union */
        if (!ptr_is_aligned(d->btf, type_id, data)) {
                memcpy(&fl, data, sz);
                flp = &fl;
        }

        switch (sz) {
        case 16:
                btf_dump_type_values(d, "%Lf", flp->ld);
                break;
        case 8:
                btf_dump_type_values(d, "%lf", flp->d);
                break;
        case 4:
                btf_dump_type_values(d, "%f", flp->f);
                break;
        default:
                pr_warn("unexpected size %d for id [%u]\n", sz, type_id);
                return -EINVAL;
        }
        return 0;
}

static int btf_dump_var_data(struct btf_dump *d,
                             const struct btf_type *v,
                             __u32 id,
                             const void *data)
{
        enum btf_func_linkage linkage = btf_var(v)->linkage;
        const struct btf_type *t;
        const char *l;
        __u32 type_id;

        switch (linkage) {
        case BTF_FUNC_STATIC:
                l = "static ";
                break;
        case BTF_FUNC_EXTERN:
                l = "extern ";
                break;
        case BTF_FUNC_GLOBAL:
        default:
                l = "";
                break;
        }

        /* format of output here is [linkage] [type] [varname] = (type)value,
         * for example "static int cpu_profile_flip = (int)1"
         */
        btf_dump_printf(d, "%s", l);
        type_id = v->type;
        t = btf__type_by_id(d->btf, type_id);
        btf_dump_emit_type_cast(d, type_id, false);
        btf_dump_printf(d, " %s = ", btf_name_of(d, v->name_off));
        return btf_dump_dump_type_data(d, NULL, t, type_id, data, 0, 0);
}

static int btf_dump_array_data(struct btf_dump *d,
                               const struct btf_type *t,
                               __u32 id,
                               const void *data)
{
        const struct btf_array *array = btf_array(t);
        const struct btf_type *elem_type;
        __u32 i, elem_type_id;
        __s64 elem_size;
        bool is_array_member;

        elem_type_id = array->type;
        elem_type = skip_mods_and_typedefs(d->btf, elem_type_id, NULL);
        elem_size = btf__resolve_size(d->btf, elem_type_id);
        if (elem_size <= 0) {
                pr_warn("unexpected elem size %zd for array type [%u]\n",
                        (ssize_t)elem_size, id);
                return -EINVAL;
        }

        if (btf_is_int(elem_type)) {
                /*
                 * BTF_INT_CHAR encoding never seems to be set for
                 * char arrays, so if size is 1 and element is
                 * printable as a char, we'll do that.
                 */
                if (elem_size == 1)
                        d->typed_dump->is_array_char = true;
        }

        /* note that we increment depth before calling btf_dump_print() below;
         * this is intentional.  btf_dump_data_newline() will not print a
         * newline for depth 0 (since this leaves us with trailing newlines
         * at the end of typed display), so depth is incremented first.
         * For similar reasons, we decrement depth before showing the closing
         * parenthesis.
         */
        d->typed_dump->depth++;
        btf_dump_printf(d, "[%s", btf_dump_data_newline(d));

        /* may be a multidimensional array, so store current "is array member"
         * status so we can restore it correctly later.
         */
        is_array_member = d->typed_dump->is_array_member;
        d->typed_dump->is_array_member = true;
        for (i = 0; i < array->nelems; i++, data += elem_size) {
                if (d->typed_dump->is_array_terminated)
                        break;
                btf_dump_dump_type_data(d, NULL, elem_type, elem_type_id, data, 0, 0);
        }
        d->typed_dump->is_array_member = is_array_member;
        d->typed_dump->depth--;
        btf_dump_data_pfx(d);
        btf_dump_type_values(d, "]");

        return 0;
}

static int btf_dump_struct_data(struct btf_dump *d,
                                const struct btf_type *t,
                                __u32 id,
                                const void *data)
{
        const struct btf_member *m = btf_members(t);
        __u16 n = btf_vlen(t);
        int i, err = 0;

        /* note that we increment depth before calling btf_dump_print() below;
         * this is intentional.  btf_dump_data_newline() will not print a
         * newline for depth 0 (since this leaves us with trailing newlines
         * at the end of typed display), so depth is incremented first.
         * For similar reasons, we decrement depth before showing the closing
         * parenthesis.
         */
        d->typed_dump->depth++;
        btf_dump_printf(d, "{%s", btf_dump_data_newline(d));

        for (i = 0; i < n; i++, m++) {
                const struct btf_type *mtype;
                const char *mname;
                __u32 moffset;
                __u8 bit_sz;

                mtype = btf__type_by_id(d->btf, m->type);
                mname = btf_name_of(d, m->name_off);
                moffset = btf_member_bit_offset(t, i);

                bit_sz = btf_member_bitfield_size(t, i);
                err = btf_dump_dump_type_data(d, mname, mtype, m->type, data + moffset / 8,
                                              moffset % 8, bit_sz);
                if (err < 0)
                        return err;
        }
        d->typed_dump->depth--;
        btf_dump_data_pfx(d);
        btf_dump_type_values(d, "}");
        return err;
}

union ptr_data {
        unsigned int p;
        unsigned long long lp;
};

static int btf_dump_ptr_data(struct btf_dump *d,
                              const struct btf_type *t,
                              __u32 id,
                              const void *data)
{
        if (ptr_is_aligned(d->btf, id, data) && d->ptr_sz == sizeof(void *)) {
                btf_dump_type_values(d, "%p", *(void **)data);
        } else {
                union ptr_data pt;

                memcpy(&pt, data, d->ptr_sz);
                if (d->ptr_sz == 4)
                        btf_dump_type_values(d, "0x%x", pt.p);
                else
                        btf_dump_type_values(d, "0x%llx", pt.lp);
        }
        return 0;
}

static int btf_dump_get_enum_value(struct btf_dump *d,
                                   const struct btf_type *t,
                                   const void *data,
                                   __u32 id,
                                   __s64 *value)
{
        bool is_signed = btf_kflag(t);

        if (!ptr_is_aligned(d->btf, id, data)) {
                __u64 val;
                int err;

                err = btf_dump_get_bitfield_value(d, t, data, 0, 0, &val);
                if (err)
                        return err;
                *value = (__s64)val;
                return 0;
        }

        switch (t->size) {
        case 8:
                *value = *(__s64 *)data;
                return 0;
        case 4:
                *value = is_signed ? (__s64)*(__s32 *)data : *(__u32 *)data;
                return 0;
        case 2:
                *value = is_signed ? *(__s16 *)data : *(__u16 *)data;
                return 0;
        case 1:
                *value = is_signed ? *(__s8 *)data : *(__u8 *)data;
                return 0;
        default:
                pr_warn("unexpected size %d for enum, id:[%u]\n", t->size, id);
                return -EINVAL;
        }
}

static int btf_dump_enum_data(struct btf_dump *d,
                              const struct btf_type *t,
                              __u32 id,
                              const void *data)
{
        bool is_signed;
        __s64 value;
        int i, err;

        err = btf_dump_get_enum_value(d, t, data, id, &value);
        if (err)
                return err;

        is_signed = btf_kflag(t);
        if (btf_is_enum(t)) {
                const struct btf_enum *e;

                for (i = 0, e = btf_enum(t); i < btf_vlen(t); i++, e++) {
                        if (value != e->val)
                                continue;
                        btf_dump_type_values(d, "%s", btf_name_of(d, e->name_off));
                        return 0;
                }

                btf_dump_type_values(d, is_signed ? "%d" : "%u", value);
        } else {
                const struct btf_enum64 *e;

                for (i = 0, e = btf_enum64(t); i < btf_vlen(t); i++, e++) {
                        if (value != btf_enum64_value(e))
                                continue;
                        btf_dump_type_values(d, "%s", btf_name_of(d, e->name_off));
                        return 0;
                }

                btf_dump_type_values(d, is_signed ? "%lldLL" : "%lluULL",
                                     (unsigned long long)value);
        }
        return 0;
}

static int btf_dump_datasec_data(struct btf_dump *d,
                                 const struct btf_type *t,
                                 __u32 id,
                                 const void *data)
{
        const struct btf_var_secinfo *vsi;
        const struct btf_type *var;
        __u32 i;
        int err;

        btf_dump_type_values(d, "SEC(\"%s\") ", btf_name_of(d, t->name_off));

        for (i = 0, vsi = btf_var_secinfos(t); i < btf_vlen(t); i++, vsi++) {
                var = btf__type_by_id(d->btf, vsi->type);
                err = btf_dump_dump_type_data(d, NULL, var, vsi->type, data + vsi->offset, 0, 0);
                if (err < 0)
                        return err;
                btf_dump_printf(d, ";");
        }
        return 0;
}

/* return size of type, or if base type overflows, return -E2BIG. */
static int btf_dump_type_data_check_overflow(struct btf_dump *d,
                                             const struct btf_type *t,
                                             __u32 id,
                                             const void *data,
                                             __u8 bits_offset,
                                             __u8 bit_sz)
{
        __s64 size;

        if (bit_sz) {
                /* bits_offset is at most 7. bit_sz is at most 128. */
                __u8 nr_bytes = (bits_offset + bit_sz + 7) / 8;

                /* When bit_sz is non zero, it is called from
                 * btf_dump_struct_data() where it only cares about
                 * negative error value.
                 * Return nr_bytes in success case to make it
                 * consistent as the regular integer case below.
                 */
                return data + nr_bytes > d->typed_dump->data_end ? -E2BIG : nr_bytes;
        }

        size = btf__resolve_size(d->btf, id);

        if (size < 0 || size >= INT_MAX) {
                pr_warn("unexpected size [%zu] for id [%u]\n",
                        (size_t)size, id);
                return -EINVAL;
        }

        /* Only do overflow checking for base types; we do not want to
         * avoid showing part of a struct, union or array, even if we
         * do not have enough data to show the full object.  By
         * restricting overflow checking to base types we can ensure
         * that partial display succeeds, while avoiding overflowing
         * and using bogus data for display.
         */
        t = skip_mods_and_typedefs(d->btf, id, NULL);
        if (!t) {
                pr_warn("unexpected error skipping mods/typedefs for id [%u]\n",
                        id);
                return -EINVAL;
        }

        switch (btf_kind(t)) {
        case BTF_KIND_INT:
        case BTF_KIND_FLOAT:
        case BTF_KIND_PTR:
        case BTF_KIND_ENUM:
        case BTF_KIND_ENUM64:
                if (data + bits_offset / 8 + size > d->typed_dump->data_end)
                        return -E2BIG;
                break;
        default:
                break;
        }
        return (int)size;
}

static int btf_dump_type_data_check_zero(struct btf_dump *d,
                                         const struct btf_type *t,
                                         __u32 id,
                                         const void *data,
                                         __u8 bits_offset,
                                         __u8 bit_sz)
{
        __s64 value;
        int i, err;

        /* toplevel exceptions; we show zero values if
         * - we ask for them (emit_zeros)
         * - if we are at top-level so we see "struct empty { }"
         * - or if we are an array member and the array is non-empty and
         *   not a char array; we don't want to be in a situation where we
         *   have an integer array 0, 1, 0, 1 and only show non-zero values.
         *   If the array contains zeroes only, or is a char array starting
         *   with a '\0', the array-level check_zero() will prevent showing it;
         *   we are concerned with determining zero value at the array member
         *   level here.
         */
        if (d->typed_dump->emit_zeroes || d->typed_dump->depth == 0 ||
            (d->typed_dump->is_array_member &&
             !d->typed_dump->is_array_char))
                return 0;

        t = skip_mods_and_typedefs(d->btf, id, NULL);

        switch (btf_kind(t)) {
        case BTF_KIND_INT:
                if (bit_sz)
                        return btf_dump_bitfield_check_zero(d, t, data, bits_offset, bit_sz);
                return btf_dump_base_type_check_zero(d, t, id, data);
        case BTF_KIND_FLOAT:
        case BTF_KIND_PTR:
                return btf_dump_base_type_check_zero(d, t, id, data);
        case BTF_KIND_ARRAY: {
                const struct btf_array *array = btf_array(t);
                const struct btf_type *elem_type;
                __u32 elem_type_id, elem_size;
                bool ischar;

                elem_type_id = array->type;
                elem_size = btf__resolve_size(d->btf, elem_type_id);
                elem_type = skip_mods_and_typedefs(d->btf, elem_type_id, NULL);

                ischar = btf_is_int(elem_type) && elem_size == 1;

                /* check all elements; if _any_ element is nonzero, all
                 * of array is displayed.  We make an exception however
                 * for char arrays where the first element is 0; these
                 * are considered zeroed also, even if later elements are
                 * non-zero because the string is terminated.
                 */
                for (i = 0; i < array->nelems; i++) {
                        if (i == 0 && ischar && *(char *)data == 0)
                                return -ENODATA;
                        err = btf_dump_type_data_check_zero(d, elem_type,
                                                            elem_type_id,
                                                            data +
                                                            (i * elem_size),
                                                            bits_offset, 0);
                        if (err != -ENODATA)
                                return err;
                }
                return -ENODATA;
        }
        case BTF_KIND_STRUCT:
        case BTF_KIND_UNION: {
                const struct btf_member *m = btf_members(t);
                __u16 n = btf_vlen(t);

                /* if any struct/union member is non-zero, the struct/union
                 * is considered non-zero and dumped.
                 */
                for (i = 0; i < n; i++, m++) {
                        const struct btf_type *mtype;
                        __u32 moffset;

                        mtype = btf__type_by_id(d->btf, m->type);
                        moffset = btf_member_bit_offset(t, i);

                        /* btf_int_bits() does not store member bitfield size;
                         * bitfield size needs to be stored here so int display
                         * of member can retrieve it.
                         */
                        bit_sz = btf_member_bitfield_size(t, i);
                        err = btf_dump_type_data_check_zero(d, mtype, m->type, data + moffset / 8,
                                                            moffset % 8, bit_sz);
                        if (err != ENODATA)
                                return err;
                }
                return -ENODATA;
        }
        case BTF_KIND_ENUM:
        case BTF_KIND_ENUM64:
                err = btf_dump_get_enum_value(d, t, data, id, &value);
                if (err)
                        return err;
                if (value == 0)
                        return -ENODATA;
                return 0;
        default:
                return 0;
        }
}

/* returns size of data dumped, or error. */
static int btf_dump_dump_type_data(struct btf_dump *d,
                                   const char *fname,
                                   const struct btf_type *t,
                                   __u32 id,
                                   const void *data,
                                   __u8 bits_offset,
                                   __u8 bit_sz)
{
        int size, err = 0;

        size = btf_dump_type_data_check_overflow(d, t, id, data, bits_offset, bit_sz);
        if (size < 0)
                return size;
        err = btf_dump_type_data_check_zero(d, t, id, data, bits_offset, bit_sz);
        if (err) {
                /* zeroed data is expected and not an error, so simply skip
                 * dumping such data.  Record other errors however.
                 */
                if (err == -ENODATA)
                        return size;
                return err;
        }
        btf_dump_data_pfx(d);

        if (!d->typed_dump->skip_names) {
                if (fname && strlen(fname) > 0)
                        btf_dump_printf(d, ".%s = ", fname);
                btf_dump_emit_type_cast(d, id, true);
        }

        t = skip_mods_and_typedefs(d->btf, id, NULL);

        switch (btf_kind(t)) {
        case BTF_KIND_UNKN:
        case BTF_KIND_FWD:
        case BTF_KIND_FUNC:
        case BTF_KIND_FUNC_PROTO:
        case BTF_KIND_DECL_TAG:
                err = btf_dump_unsupported_data(d, t, id);
                break;
        case BTF_KIND_INT:
                if (bit_sz)
                        err = btf_dump_bitfield_data(d, t, data, bits_offset, bit_sz);
                else
                        err = btf_dump_int_data(d, t, id, data, bits_offset);
                break;
        case BTF_KIND_FLOAT:
                err = btf_dump_float_data(d, t, id, data);
                break;
        case BTF_KIND_PTR:
                err = btf_dump_ptr_data(d, t, id, data);
                break;
        case BTF_KIND_ARRAY:
                err = btf_dump_array_data(d, t, id, data);
                break;
        case BTF_KIND_STRUCT:
        case BTF_KIND_UNION:
                err = btf_dump_struct_data(d, t, id, data);
                break;
        case BTF_KIND_ENUM:
        case BTF_KIND_ENUM64:
                /* handle bitfield and int enum values */
                if (bit_sz) {
                        __u64 print_num;
                        __s64 enum_val;

                        err = btf_dump_get_bitfield_value(d, t, data, bits_offset, bit_sz,
                                                          &print_num);
                        if (err)
                                break;
                        enum_val = (__s64)print_num;
                        err = btf_dump_enum_data(d, t, id, &enum_val);
                } else
                        err = btf_dump_enum_data(d, t, id, data);
                break;
        case BTF_KIND_VAR:
                err = btf_dump_var_data(d, t, id, data);
                break;
        case BTF_KIND_DATASEC:
                err = btf_dump_datasec_data(d, t, id, data);
                break;
        default:
                pr_warn("unexpected kind [%u] for id [%u]\n",
                        BTF_INFO_KIND(t->info), id);
                return -EINVAL;
        }
        if (err < 0)
                return err;
        return size;
}

int btf_dump__dump_type_data(struct btf_dump *d, __u32 id,
                             const void *data, size_t data_sz,
                             const struct btf_dump_type_data_opts *opts)
{
        struct btf_dump_data typed_dump = {};
        const struct btf_type *t;
        int ret;

        if (!OPTS_VALID(opts, btf_dump_type_data_opts))
                return libbpf_err(-EINVAL);

        t = btf__type_by_id(d->btf, id);
        if (!t)
                return libbpf_err(-ENOENT);

        d->typed_dump = &typed_dump;
        d->typed_dump->data_end = data + data_sz;
        d->typed_dump->indent_lvl = OPTS_GET(opts, indent_level, 0);

        /* default indent string is a tab */
        if (!OPTS_GET(opts, indent_str, NULL))
                d->typed_dump->indent_str[0] = '\t';
        else
                libbpf_strlcpy(d->typed_dump->indent_str, opts->indent_str,
                               sizeof(d->typed_dump->indent_str));

        d->typed_dump->compact = OPTS_GET(opts, compact, false);
        d->typed_dump->skip_names = OPTS_GET(opts, skip_names, false);
        d->typed_dump->emit_zeroes = OPTS_GET(opts, emit_zeroes, false);

        ret = btf_dump_dump_type_data(d, NULL, t, id, data, 0, 0);

        d->typed_dump = NULL;

        return libbpf_err(ret);
}