arch/arc/kernel/stacktrace.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  *      stacktrace.c : stacktracing APIs needed by rest of kernel
   4  *                      (wrappers over ARC dwarf based unwinder)
   5  *
   6  * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
   7  *
   8  *  vineetg: aug 2009
   9  *  -Implemented CONFIG_STACKTRACE APIs, primarily save_stack_trace_tsk( )
  10  *   for displaying task's kernel mode call stack in /proc/<pid>/stack
  11  *  -Iterator based approach to have single copy of unwinding core and APIs
  12  *   needing unwinding, implement the logic in iterator regarding:
  13  *      = which frame onwards to start capture
  14  *      = which frame to stop capturing (wchan)
  15  *      = specifics of data structs where trace is saved(CONFIG_STACKTRACE etc)
  16  *
  17  *  vineetg: March 2009
  18  *  -Implemented correct versions of thread_saved_pc() and get_wchan()
  19  *
  20  *  rajeshwarr: 2008
  21  *  -Initial implementation
  22  */
  23
  24 #include <linux/ptrace.h>
  25 #include <linux/export.h>
  26 #include <linux/stacktrace.h>
  27 #include <linux/kallsyms.h>
  28 #include <linux/sched/debug.h>
  29
  30 #include <asm/arcregs.h>
  31 #include <asm/unwind.h>
  32 #include <asm/switch_to.h>
  33
  34 /*-------------------------------------------------------------------------
  35  *              Unwinder Iterator
  36  *-------------------------------------------------------------------------
  37  */
  38
  39 #ifdef CONFIG_ARC_DW2_UNWIND
  40
  41 static int
  42 seed_unwind_frame_info(struct task_struct *tsk, struct pt_regs *regs,
  43                        struct unwind_frame_info *frame_info)
  44 {
  45         /*
  46          * synchronous unwinding (e.g. dump_stack)
  47          *  - uses current values of SP and friends
  48          */
  49         if (regs == NULL && (tsk == NULL || tsk == current)) {
  50                 unsigned long fp, sp, blink, ret;
  51                 frame_info->task = current;
  52
  53                 __asm__ __volatile__(
  54                         "mov %0,r27\n\t"
  55                         "mov %1,r28\n\t"
  56                         "mov %2,r31\n\t"
  57                         "mov %3,r63\n\t"
  58                         : "=r"(fp), "=r"(sp), "=r"(blink), "=r"(ret)
  59                 );
  60
  61                 frame_info->regs.r27 = fp;
  62                 frame_info->regs.r28 = sp;
  63                 frame_info->regs.r31 = blink;
  64                 frame_info->regs.r63 = ret;
  65                 frame_info->call_frame = 0;
  66         } else if (regs == NULL) {
  67                 /*
  68                  * Asynchronous unwinding of a likely sleeping task
  69                  *  - first ensure it is actually sleeping
  70                  *  - if so, it will be in __switch_to, kernel mode SP of task
  71                  *    is safe-kept and BLINK at a well known location in there
  72                  */
  73
  74                 if (tsk->state == TASK_RUNNING)
  75                         return -1;
  76
  77                 frame_info->task = tsk;
  78
  79                 frame_info->regs.r27 = TSK_K_FP(tsk);
  80                 frame_info->regs.r28 = TSK_K_ESP(tsk);
  81                 frame_info->regs.r31 = TSK_K_BLINK(tsk);
  82                 frame_info->regs.r63 = (unsigned int)__switch_to;
  83
  84                 /* In the prologue of __switch_to, first FP is saved on stack
  85                  * and then SP is copied to FP. Dwarf assumes cfa as FP based
  86                  * but we didn't save FP. The value retrieved above is FP's
  87                  * state in previous frame.
  88                  * As a work around for this, we unwind from __switch_to start
  89                  * and adjust SP accordingly. The other limitation is that
  90                  * __switch_to macro is dwarf rules are not generated for inline
  91                  * assembly code
  92                  */
  93                 frame_info->regs.r27 = 0;
  94                 frame_info->regs.r28 += 60;
  95                 frame_info->call_frame = 0;
  96
  97         } else {
  98                 /*
  99                  * Asynchronous unwinding of intr/exception
 100                  *  - Just uses the pt_regs passed
 101                  */
 102                 frame_info->task = tsk;
 103
 104                 frame_info->regs.r27 = regs->fp;
 105                 frame_info->regs.r28 = regs->sp;
 106                 frame_info->regs.r31 = regs->blink;
 107                 frame_info->regs.r63 = regs->ret;
 108                 frame_info->call_frame = 0;
 109         }
 110
 111         return 0;
 112 }
 113
 114 #endif
 115
 116 notrace noinline unsigned int
 117 arc_unwind_core(struct task_struct *tsk, struct pt_regs *regs,
 118                 int (*consumer_fn) (unsigned int, void *), void *arg)
 119 {
 120 #ifdef CONFIG_ARC_DW2_UNWIND
 121         int ret = 0, cnt = 0;
 122         unsigned int address;
 123         struct unwind_frame_info frame_info;
 124
 125         if (seed_unwind_frame_info(tsk, regs, &frame_info))
 126                 return 0;
 127
 128         while (1) {
 129                 address = UNW_PC(&frame_info);
 130
 131                 if (!address || !__kernel_text_address(address))
 132                         break;
 133
 134                 if (consumer_fn(address, arg) == -1)
 135                         break;
 136
 137                 ret = arc_unwind(&frame_info);
 138                 if (ret)
 139                         break;
 140
 141                 frame_info.regs.r63 = frame_info.regs.r31;
 142
 143                 if (cnt++ > 128) {
 144                         printk("unwinder looping too long, aborting !\n");
 145                         return 0;
 146                 }
 147         }
 148
 149         return address;         /* return the last address it saw */
 150 #else
 151         /* On ARC, only Dward based unwinder works. fp based backtracing is
 152          * not possible (-fno-omit-frame-pointer) because of the way function
 153          * prelogue is setup (callee regs saved and then fp set and not other
 154          * way around
 155          */
 156         pr_warn_once("CONFIG_ARC_DW2_UNWIND needs to be enabled\n");
 157         return 0;
 158
 159 #endif
 160 }
 161
 162 /*-------------------------------------------------------------------------
 163  * callbacks called by unwinder iterator to implement kernel APIs
 164  *
 165  * The callback can return -1 to force the iterator to stop, which by default
 166  * keeps going till the bottom-most frame.
 167  *-------------------------------------------------------------------------
 168  */
 169
 170 /* Call-back which plugs into unwinding core to dump the stack in
 171  * case of panic/OOPs/BUG etc
 172  */
 173 static int __print_sym(unsigned int address, void *unused)
 174 {
 175         printk("  %pS\n", (void *)address);
 176         return 0;
 177 }
 178
 179 #ifdef CONFIG_STACKTRACE
 180
 181 /* Call-back which plugs into unwinding core to capture the
 182  * traces needed by kernel on /proc/<pid>/stack
 183  */
 184 static int __collect_all(unsigned int address, void *arg)
 185 {
 186         struct stack_trace *trace = arg;
 187
 188         if (trace->skip > 0)
 189                 trace->skip--;
 190         else
 191                 trace->entries[trace->nr_entries++] = address;
 192
 193         if (trace->nr_entries >= trace->max_entries)
 194                 return -1;
 195
 196         return 0;
 197 }
 198
 199 static int __collect_all_but_sched(unsigned int address, void *arg)
 200 {
 201         struct stack_trace *trace = arg;
 202
 203         if (in_sched_functions(address))
 204                 return 0;
 205
 206         if (trace->skip > 0)
 207                 trace->skip--;
 208         else
 209                 trace->entries[trace->nr_entries++] = address;
 210
 211         if (trace->nr_entries >= trace->max_entries)
 212                 return -1;
 213
 214         return 0;
 215 }
 216
 217 #endif
 218
 219 static int __get_first_nonsched(unsigned int address, void *unused)
 220 {
 221         if (in_sched_functions(address))
 222                 return 0;
 223
 224         return -1;
 225 }
 226
 227 /*-------------------------------------------------------------------------
 228  *              APIs expected by various kernel sub-systems
 229  *-------------------------------------------------------------------------
 230  */
 231
 232 noinline void show_stacktrace(struct task_struct *tsk, struct pt_regs *regs)
 233 {
 234         pr_info("\nStack Trace:\n");
 235         arc_unwind_core(tsk, regs, __print_sym, NULL);
 236 }
 237 EXPORT_SYMBOL(show_stacktrace);
 238
 239 /* Expected by sched Code */
 240 void show_stack(struct task_struct *tsk, unsigned long *sp)
 241 {
 242         show_stacktrace(tsk, NULL);
 243 }
 244
 245 /* Another API expected by schedular, shows up in "ps" as Wait Channel
 246  * Of course just returning schedule( ) would be pointless so unwind until
 247  * the function is not in schedular code
 248  */
 249 unsigned int get_wchan(struct task_struct *tsk)
 250 {
 251         return arc_unwind_core(tsk, NULL, __get_first_nonsched, NULL);
 252 }
 253
 254 #ifdef CONFIG_STACKTRACE
 255
 256 /*
 257  * API required by CONFIG_STACKTRACE, CONFIG_LATENCYTOP.
 258  * A typical use is when /proc/<pid>/stack is queried by userland
 259  */
 260 void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
 261 {
 262         /* Assumes @tsk is sleeping so unwinds from __switch_to */
 263         arc_unwind_core(tsk, NULL, __collect_all_but_sched, trace);
 264 }
 265
 266 void save_stack_trace(struct stack_trace *trace)
 267 {
 268         /* Pass NULL for task so it unwinds the current call frame */
 269         arc_unwind_core(NULL, NULL, __collect_all, trace);
 270 }
 271 EXPORT_SYMBOL_GPL(save_stack_trace);
 272 #endif