libubacktrace/backtrace.c

   1 /*
   2  * Perform stack unwinding by using the _Unwind_Backtrace.
   3  *
   4  * User application that wants to use backtrace needs to be
   5  * compiled with -fasynchronous-unwind-tables option and -rdynamic to get full
   6  * symbols printed.
   7  *
   8  * Copyright (C) 2009, 2010 STMicroelectronics Ltd.
   9  *
  10  * Author(s): Giuseppe Cavallaro <peppe.cavallaro@st.com>
  11  * - Initial implementation for glibc
  12  *
  13  * Author(s): Carmelo Amoroso <carmelo.amoroso@st.com>
  14  * - Reworked for uClibc
  15  *   - use dlsym/dlopen from libdl
  16  *   - rewrite initialisation to not use libc_once
  17  *   - make it available in static link too
  18  *
  19  * Licensed under the LGPL v2.1, see the file COPYING.LIB in this tarball.
  20  *
  21  */
  22
  23 #include <libgcc_s.h>
  24 #include <execinfo.h>
  25 #include <dlfcn.h>
  26 #include <stdlib.h>
  27 #include <unwind.h>
  28 #include <assert.h>
  29 #include <stdio.h>
  30
  31 struct trace_arg
  32 {
  33   void **array;
  34   int cnt, size;
  35 };
  36
  37 #ifdef SHARED
  38 static _Unwind_Reason_Code (*unwind_backtrace) (_Unwind_Trace_Fn, void *);
  39 static _Unwind_Ptr (*unwind_getip) (struct _Unwind_Context *);
  40
  41 static void backtrace_init (void)
  42 {
  43         void *handle = dlopen (LIBGCC_S_SO, RTLD_LAZY);
  44
  45         if (handle == NULL
  46                 || ((unwind_backtrace = dlsym (handle, "_Unwind_Backtrace")) == NULL)
  47                 || ((unwind_getip = dlsym (handle, "_Unwind_GetIP")) == NULL)) {
  48                 printf(LIBGCC_S_SO " must be installed for backtrace to work\n");
  49                 abort();
  50         }
  51 }
  52 #else
  53 # define unwind_backtrace _Unwind_Backtrace
  54 # define unwind_getip _Unwind_GetIP
  55 #endif
  56
  57 static _Unwind_Reason_Code
  58 backtrace_helper (struct _Unwind_Context *ctx, void *a)
  59 {
  60         struct trace_arg *arg = a;
  61
  62         assert (unwind_getip != NULL);
  63
  64         /* We are first called with address in the __backtrace function. Skip it. */
  65         if (arg->cnt != -1)
  66                 arg->array[arg->cnt] = (void *) unwind_getip (ctx);
  67         if (++arg->cnt == arg->size)
  68                 return _URC_END_OF_STACK;
  69         return _URC_NO_REASON;
  70 }
  71
  72 /*
  73  * Perform stack unwinding by using the _Unwind_Backtrace.
  74  *
  75  */
  76 int backtrace (void **array, int size)
  77 {
  78         struct trace_arg arg = { .array = array, .size = size, .cnt = -1 };
  79
  80 #ifdef SHARED
  81         if (unwind_backtrace == NULL)
  82                 backtrace_init();
  83 #endif
  84
  85         if (size >= 1)
  86                 unwind_backtrace (backtrace_helper, &arg);
  87
  88         return arg.cnt != -1 ? arg.cnt : 0;
  89 }