debug/backtrace.c

   1 /* Return backtrace of current program state.
   2    Copyright (C) 2003-2024 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <execinfo.h>
  20 #include <stdlib.h>
  21 #include <unwind.h>
  22 #include <unwind-link.h>
  23
  24 struct trace_arg
  25 {
  26   void **array;
  27   struct unwind_link *unwind_link;
  28   _Unwind_Word cfa;
  29   int cnt;
  30   int size;
  31 };
  32
  33 static _Unwind_Reason_Code
  34 backtrace_helper (struct _Unwind_Context *ctx, void *a)
  35 {
  36   struct trace_arg *arg = a;
  37
  38   /* We are first called with address in the __backtrace function.
  39      Skip it.  */
  40   if (arg->cnt != -1)
  41     {
  42       arg->array[arg->cnt]
  43         = (void *) UNWIND_LINK_PTR (arg->unwind_link, _Unwind_GetIP) (ctx);
  44       if (arg->cnt > 0)
  45         arg->array[arg->cnt]
  46           = unwind_arch_adjustment (arg->array[arg->cnt - 1],
  47                                     arg->array[arg->cnt]);
  48
  49       /* Check whether we make any progress.  */
  50       _Unwind_Word cfa
  51         = UNWIND_LINK_PTR (arg->unwind_link, _Unwind_GetCFA) (ctx);
  52
  53       if (arg->cnt > 0 && arg->array[arg->cnt - 1] == arg->array[arg->cnt]
  54          && cfa == arg->cfa)
  55        return _URC_END_OF_STACK;
  56       arg->cfa = cfa;
  57     }
  58   if (++arg->cnt == arg->size)
  59     return _URC_END_OF_STACK;
  60   return _URC_NO_REASON;
  61 }
  62
  63 int
  64 __backtrace (void **array, int size)
  65 {
  66   struct trace_arg arg =
  67     {
  68      .array = array,
  69      .unwind_link = __libc_unwind_link_get (),
  70      .cfa = 0,
  71      .size = size,
  72      .cnt = -1
  73     };
  74
  75   if (size <= 0 || arg.unwind_link == NULL)
  76     return 0;
  77
  78   UNWIND_LINK_PTR (arg.unwind_link, _Unwind_Backtrace)
  79     (backtrace_helper, &arg);
  80
  81   /* _Unwind_Backtrace seems to put NULL address above
  82      _start.  Fix it up here.  */
  83   if (arg.cnt > 1 && arg.array[arg.cnt - 1] == NULL)
  84     --arg.cnt;
  85   return arg.cnt != -1 ? arg.cnt : 0;
  86 }
  87 weak_alias (__backtrace, backtrace)
  88 libc_hidden_def (__backtrace)