2 * Post mortem Dwarf CFI based unwinding on top of regs and stack dumps.
4 * Lots of this code have been borrowed or heavily inspired from parts of
5 * the libunwind 0.99 code which are (amongst other contributors I may have
8 * Copyright (C) 2002-2007 Hewlett-Packard Co
9 * Contributed by David Mosberger-Tang <davidm@hpl.hp.com>
11 * And the bugs have been added by:
13 * Copyright (C) 2010, Frederic Weisbecker <fweisbec@gmail.com>
14 * Copyright (C) 2012, Jiri Olsa <jolsa@redhat.com>
24 #include <linux/list.h>
25 #include <libunwind.h>
26 #include <libunwind-ptrace.h>
27 #include "callchain.h"
30 #include "perf_regs.h"
37 UNW_OBJ(dwarf_search_unwind_table) (unw_addr_space_t as,
41 int need_unwind_info, void *arg);
43 #define dwarf_search_unwind_table UNW_OBJ(dwarf_search_unwind_table)
46 UNW_OBJ(dwarf_find_debug_frame) (int found, unw_dyn_info_t *di_debug,
49 const char *obj_name, unw_word_t start,
52 #define dwarf_find_debug_frame UNW_OBJ(dwarf_find_debug_frame)
54 #define DW_EH_PE_FORMAT_MASK 0x0f /* format of the encoded value */
55 #define DW_EH_PE_APPL_MASK 0x70 /* how the value is to be applied */
57 /* Pointer-encoding formats: */
58 #define DW_EH_PE_omit 0xff
59 #define DW_EH_PE_ptr 0x00 /* pointer-sized unsigned value */
60 #define DW_EH_PE_udata4 0x03 /* unsigned 32-bit value */
61 #define DW_EH_PE_udata8 0x04 /* unsigned 64-bit value */
62 #define DW_EH_PE_sdata4 0x0b /* signed 32-bit value */
63 #define DW_EH_PE_sdata8 0x0c /* signed 64-bit value */
65 /* Pointer-encoding application: */
66 #define DW_EH_PE_absptr 0x00 /* absolute value */
67 #define DW_EH_PE_pcrel 0x10 /* rel. to addr. of encoded value */
70 * The following are not documented by LSB v1.3, yet they are used by
71 * GCC, presumably they aren't documented by LSB since they aren't
74 #define DW_EH_PE_funcrel 0x40 /* start-of-procedure-relative */
75 #define DW_EH_PE_aligned 0x50 /* aligned pointer */
77 /* Flags intentionaly not handled, since they're not needed:
78 * #define DW_EH_PE_indirect 0x80
79 * #define DW_EH_PE_uleb128 0x01
80 * #define DW_EH_PE_udata2 0x02
81 * #define DW_EH_PE_sleb128 0x09
82 * #define DW_EH_PE_sdata2 0x0a
83 * #define DW_EH_PE_textrel 0x20
84 * #define DW_EH_PE_datarel 0x30
88 struct perf_sample *sample;
89 struct machine *machine;
90 struct thread *thread;
93 #define dw_read(ptr, type, end) ({ \
94 type *__p = (type *) ptr; \
96 if ((__p + 1) > (type *) end) \
99 ptr = (typeof(ptr)) __p; \
103 static int __dw_read_encoded_value(u8 **p, u8 *end, u64 *val,
114 *val = dw_read(cur, unsigned long, end);
120 switch (encoding & DW_EH_PE_APPL_MASK) {
121 case DW_EH_PE_absptr:
124 *val = (unsigned long) cur;
130 if ((encoding & 0x07) == 0x00)
131 encoding |= DW_EH_PE_udata4;
133 switch (encoding & DW_EH_PE_FORMAT_MASK) {
134 case DW_EH_PE_sdata4:
135 *val += dw_read(cur, s32, end);
137 case DW_EH_PE_udata4:
138 *val += dw_read(cur, u32, end);
140 case DW_EH_PE_sdata8:
141 *val += dw_read(cur, s64, end);
143 case DW_EH_PE_udata8:
144 *val += dw_read(cur, u64, end);
155 #define dw_read_encoded_value(ptr, end, enc) ({ \
157 if (__dw_read_encoded_value(&ptr, end, &__v, enc)) { \
163 static u64 elf_section_offset(int fd, const char *name)
170 elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
175 if (gelf_getehdr(elf, &ehdr) == NULL)
178 if (!elf_section_by_name(elf, &ehdr, &shdr, name, NULL))
181 offset = shdr.sh_offset;
188 #ifndef NO_LIBUNWIND_DEBUG_FRAME
189 static int elf_is_exec(int fd, const char *name)
195 elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
198 if (gelf_getehdr(elf, &ehdr) == NULL)
201 retval = (ehdr.e_type == ET_EXEC);
205 pr_debug("unwind: elf_is_exec(%s): %d\n", name, retval);
215 struct eh_frame_hdr {
216 unsigned char version;
217 unsigned char eh_frame_ptr_enc;
218 unsigned char fde_count_enc;
219 unsigned char table_enc;
222 * The rest of the header is variable-length and consists of the
225 * encoded_t eh_frame_ptr;
226 * encoded_t fde_count;
229 /* A single encoded pointer should not be more than 8 bytes. */
234 * encoded_t start_ip;
235 * encoded_t fde_addr;
236 * } binary_search_table[fde_count];
241 static int unwind_spec_ehframe(struct dso *dso, struct machine *machine,
242 u64 offset, u64 *table_data, u64 *segbase,
245 struct eh_frame_hdr hdr;
246 u8 *enc = (u8 *) &hdr.enc;
247 u8 *end = (u8 *) &hdr.data;
250 r = dso__data_read_offset(dso, machine, offset,
251 (u8 *) &hdr, sizeof(hdr));
252 if (r != sizeof(hdr))
255 /* We dont need eh_frame_ptr, just skip it. */
256 dw_read_encoded_value(enc, end, hdr.eh_frame_ptr_enc);
258 *fde_count = dw_read_encoded_value(enc, end, hdr.fde_count_enc);
260 *table_data = (enc - (u8 *) &hdr) + offset;
264 static int read_unwind_spec_eh_frame(struct dso *dso, struct machine *machine,
265 u64 *table_data, u64 *segbase,
268 int ret = -EINVAL, fd;
269 u64 offset = dso->data.eh_frame_hdr_offset;
272 fd = dso__data_get_fd(dso, machine);
276 /* Check the .eh_frame section for unwinding info */
277 offset = elf_section_offset(fd, ".eh_frame_hdr");
278 dso->data.eh_frame_hdr_offset = offset;
279 dso__data_put_fd(dso);
283 ret = unwind_spec_ehframe(dso, machine, offset,
290 #ifndef NO_LIBUNWIND_DEBUG_FRAME
291 static int read_unwind_spec_debug_frame(struct dso *dso,
292 struct machine *machine, u64 *offset)
295 u64 ofs = dso->data.debug_frame_offset;
298 fd = dso__data_get_fd(dso, machine);
302 /* Check the .debug_frame section for unwinding info */
303 ofs = elf_section_offset(fd, ".debug_frame");
304 dso->data.debug_frame_offset = ofs;
305 dso__data_put_fd(dso);
316 static struct map *find_map(unw_word_t ip, struct unwind_info *ui)
318 struct addr_location al;
320 thread__find_addr_map(ui->thread, PERF_RECORD_MISC_USER,
321 MAP__FUNCTION, ip, &al);
326 find_proc_info(unw_addr_space_t as, unw_word_t ip, unw_proc_info_t *pi,
327 int need_unwind_info, void *arg)
329 struct unwind_info *ui = arg;
332 u64 table_data, segbase, fde_count;
335 map = find_map(ip, ui);
336 if (!map || !map->dso)
339 pr_debug("unwind: find_proc_info dso %s\n", map->dso->name);
341 /* Check the .eh_frame section for unwinding info */
342 if (!read_unwind_spec_eh_frame(map->dso, ui->machine,
343 &table_data, &segbase, &fde_count)) {
344 memset(&di, 0, sizeof(di));
345 di.format = UNW_INFO_FORMAT_REMOTE_TABLE;
346 di.start_ip = map->start;
347 di.end_ip = map->end;
348 di.u.rti.segbase = map->start + segbase;
349 di.u.rti.table_data = map->start + table_data;
350 di.u.rti.table_len = fde_count * sizeof(struct table_entry)
351 / sizeof(unw_word_t);
352 ret = dwarf_search_unwind_table(as, ip, &di, pi,
353 need_unwind_info, arg);
356 #ifndef NO_LIBUNWIND_DEBUG_FRAME
357 /* Check the .debug_frame section for unwinding info */
359 !read_unwind_spec_debug_frame(map->dso, ui->machine, &segbase)) {
360 int fd = dso__data_get_fd(map->dso, ui->machine);
361 int is_exec = elf_is_exec(fd, map->dso->name);
362 unw_word_t base = is_exec ? 0 : map->start;
366 dso__data_put_fd(map->dso);
368 symfile = map->dso->symsrc_filename ?: map->dso->name;
370 memset(&di, 0, sizeof(di));
371 if (dwarf_find_debug_frame(0, &di, ip, base, symfile,
372 map->start, map->end))
373 return dwarf_search_unwind_table(as, ip, &di, pi,
374 need_unwind_info, arg);
381 static int access_fpreg(unw_addr_space_t __maybe_unused as,
382 unw_regnum_t __maybe_unused num,
383 unw_fpreg_t __maybe_unused *val,
384 int __maybe_unused __write,
385 void __maybe_unused *arg)
387 pr_err("unwind: access_fpreg unsupported\n");
391 static int get_dyn_info_list_addr(unw_addr_space_t __maybe_unused as,
392 unw_word_t __maybe_unused *dil_addr,
393 void __maybe_unused *arg)
398 static int resume(unw_addr_space_t __maybe_unused as,
399 unw_cursor_t __maybe_unused *cu,
400 void __maybe_unused *arg)
402 pr_err("unwind: resume unsupported\n");
407 get_proc_name(unw_addr_space_t __maybe_unused as,
408 unw_word_t __maybe_unused addr,
409 char __maybe_unused *bufp, size_t __maybe_unused buf_len,
410 unw_word_t __maybe_unused *offp, void __maybe_unused *arg)
412 pr_err("unwind: get_proc_name unsupported\n");
416 static int access_dso_mem(struct unwind_info *ui, unw_word_t addr,
419 struct addr_location al;
422 thread__find_addr_map(ui->thread, PERF_RECORD_MISC_USER,
423 MAP__FUNCTION, addr, &al);
425 pr_debug("unwind: no map for %lx\n", (unsigned long)addr);
432 size = dso__data_read_addr(al.map->dso, al.map, ui->machine,
433 addr, (u8 *) data, sizeof(*data));
435 return !(size == sizeof(*data));
438 static int access_mem(unw_addr_space_t __maybe_unused as,
439 unw_word_t addr, unw_word_t *valp,
440 int __write, void *arg)
442 struct unwind_info *ui = arg;
443 struct stack_dump *stack = &ui->sample->user_stack;
448 /* Don't support write, probably not needed. */
449 if (__write || !stack || !ui->sample->user_regs.regs) {
454 ret = perf_reg_value(&start, &ui->sample->user_regs, PERF_REG_SP);
458 end = start + stack->size;
460 /* Check overflow. */
461 if (addr + sizeof(unw_word_t) < addr)
464 if (addr < start || addr + sizeof(unw_word_t) >= end) {
465 ret = access_dso_mem(ui, addr, valp);
467 pr_debug("unwind: access_mem %p not inside range"
468 " 0x%" PRIx64 "-0x%" PRIx64 "\n",
469 (void *) (uintptr_t) addr, start, end);
476 offset = addr - start;
477 *valp = *(unw_word_t *)&stack->data[offset];
478 pr_debug("unwind: access_mem addr %p val %lx, offset %d\n",
479 (void *) (uintptr_t) addr, (unsigned long)*valp, offset);
483 static int access_reg(unw_addr_space_t __maybe_unused as,
484 unw_regnum_t regnum, unw_word_t *valp,
485 int __write, void *arg)
487 struct unwind_info *ui = arg;
491 /* Don't support write, I suspect we don't need it. */
493 pr_err("unwind: access_reg w %d\n", regnum);
497 if (!ui->sample->user_regs.regs) {
502 id = libunwind__arch_reg_id(regnum);
506 ret = perf_reg_value(&val, &ui->sample->user_regs, id);
508 pr_err("unwind: can't read reg %d\n", regnum);
512 *valp = (unw_word_t) val;
513 pr_debug("unwind: reg %d, val %lx\n", regnum, (unsigned long)*valp);
517 static void put_unwind_info(unw_addr_space_t __maybe_unused as,
518 unw_proc_info_t *pi __maybe_unused,
519 void *arg __maybe_unused)
521 pr_debug("unwind: put_unwind_info called\n");
524 static int entry(u64 ip, struct thread *thread,
525 unwind_entry_cb_t cb, void *arg)
527 struct unwind_entry e;
528 struct addr_location al;
530 thread__find_addr_location(thread, PERF_RECORD_MISC_USER,
531 MAP__FUNCTION, ip, &al);
537 pr_debug("unwind: %s:ip = 0x%" PRIx64 " (0x%" PRIx64 ")\n",
538 al.sym ? al.sym->name : "''",
540 al.map ? al.map->map_ip(al.map, ip) : (u64) 0);
545 static void display_error(int err)
549 pr_err("unwind: Only supports local.\n");
552 pr_err("unwind: Unspecified error.\n");
555 pr_err("unwind: Register unavailable.\n");
562 static unw_accessors_t accessors = {
563 .find_proc_info = find_proc_info,
564 .put_unwind_info = put_unwind_info,
565 .get_dyn_info_list_addr = get_dyn_info_list_addr,
566 .access_mem = access_mem,
567 .access_reg = access_reg,
568 .access_fpreg = access_fpreg,
570 .get_proc_name = get_proc_name,
573 int unwind__prepare_access(struct thread *thread)
575 unw_addr_space_t addr_space;
577 if (callchain_param.record_mode != CALLCHAIN_DWARF)
580 addr_space = unw_create_addr_space(&accessors, 0);
582 pr_err("unwind: Can't create unwind address space.\n");
586 unw_set_caching_policy(addr_space, UNW_CACHE_GLOBAL);
587 thread__set_priv(thread, addr_space);
592 void unwind__flush_access(struct thread *thread)
594 unw_addr_space_t addr_space;
596 if (callchain_param.record_mode != CALLCHAIN_DWARF)
599 addr_space = thread__priv(thread);
600 unw_flush_cache(addr_space, 0, 0);
603 void unwind__finish_access(struct thread *thread)
605 unw_addr_space_t addr_space;
607 if (callchain_param.record_mode != CALLCHAIN_DWARF)
610 addr_space = thread__priv(thread);
611 unw_destroy_addr_space(addr_space);
614 static int get_entries(struct unwind_info *ui, unwind_entry_cb_t cb,
615 void *arg, int max_stack)
617 unw_addr_space_t addr_space;
621 addr_space = thread__priv(ui->thread);
622 if (addr_space == NULL)
625 ret = unw_init_remote(&c, addr_space, ui);
629 while (!ret && (unw_step(&c) > 0) && max_stack--) {
632 unw_get_reg(&c, UNW_REG_IP, &ip);
633 ret = ip ? entry(ip, ui->thread, cb, arg) : 0;
639 int unwind__get_entries(unwind_entry_cb_t cb, void *arg,
640 struct thread *thread,
641 struct perf_sample *data, int max_stack)
644 struct unwind_info ui = {
647 .machine = thread->mg->machine,
651 if (!data->user_regs.regs)
654 ret = perf_reg_value(&ip, &data->user_regs, PERF_REG_IP);
658 ret = entry(ip, thread, cb, arg);
662 return --max_stack > 0 ? get_entries(&ui, cb, arg, max_stack) : 0;