libubacktrace/arm/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-unwid-tables option and -rdynamic i
   6  * to get full symbols printed.
   7  *
   8  * Author(s): Khem Raj <raj.khem@gmail.com>
   9  * - ARM specific implementation of backtrace
  10  *
  11  * Licensed under the LGPL v2.1, see the file COPYING.LIB in this tarball.
  12  *
  13  */
  14
  15 #include <libgcc_s.h>
  16 #include <execinfo.h>
  17 #include <dlfcn.h>
  18 #include <stdlib.h>
  19 #include <unwind.h>
  20 #include <assert.h>
  21 #include <stdio.h>
  22
  23 struct trace_arg
  24 {
  25   void **array;
  26   int cnt, size;
  27 };
  28
  29 #ifdef SHARED
  30 static _Unwind_Reason_Code (*unwind_backtrace) (_Unwind_Trace_Fn, void *);
  31 static _Unwind_VRS_Result (*unwind_vrs_get) (_Unwind_Context *,
  32                                              _Unwind_VRS_RegClass,
  33                                              _uw,
  34                                              _Unwind_VRS_DataRepresentation,
  35                                              void *);
  36
  37 static void backtrace_init (void)
  38 {
  39         void *handle = dlopen (LIBGCC_S_SO, RTLD_LAZY);
  40         if (handle == NULL
  41                 || ((unwind_backtrace = dlsym (handle, "_Unwind_Backtrace")) == NULL)
  42                 || ((unwind_vrs_get = dlsym (handle, "_Unwind_VRS_Get")) == NULL)) {
  43                 printf(LIBGCC_S_SO " must be installed for backtrace to work\n");
  44                 abort();
  45         }
  46 }
  47 #else
  48 # define unwind_backtrace _Unwind_Backtrace
  49 # define unwind_vrs_get _Unwind_VRS_Get
  50 #endif
  51 /* This function is identical to "_Unwind_GetGR", except that it uses
  52    "unwind_vrs_get" instead of "_Unwind_VRS_Get".  */
  53 static inline _Unwind_Word
  54 unwind_getgr (_Unwind_Context *context, int regno)
  55 {
  56   _uw val;
  57   unwind_vrs_get (context, _UVRSC_CORE, regno, _UVRSD_UINT32, &val);
  58   return val;
  59 }
  60
  61 /* This macro is identical to the _Unwind_GetIP macro, except that it
  62    uses "unwind_getgr" instead of "_Unwind_GetGR".  */
  63 #define unwind_getip(context) \
  64  (unwind_getgr (context, 15) & ~(_Unwind_Word)1)
  65
  66 static _Unwind_Reason_Code
  67 backtrace_helper (struct _Unwind_Context *ctx, void *a)
  68 {
  69         struct trace_arg *arg = a;
  70
  71         assert (unwind_getip(ctx) != NULL);
  72
  73         /* We are first called with address in the __backtrace function. Skip it. */
  74         if (arg->cnt != -1)
  75                 arg->array[arg->cnt] = (void *) unwind_getip (ctx);
  76         if (++arg->cnt == arg->size)
  77                 return _URC_END_OF_STACK;
  78         return _URC_NO_REASON;
  79 }
  80
  81 /*
  82  * Perform stack unwinding by using the _Unwind_Backtrace.
  83  *
  84  */
  85 int backtrace (void **array, int size)
  86 {
  87         struct trace_arg arg = { .array = array, .size = size, .cnt = -1 };
  88
  89 #ifdef SHARED
  90         if (unwind_backtrace == NULL)
  91                 backtrace_init();
  92 #endif
  93
  94         if (size >= 1)
  95                 unwind_backtrace (backtrace_helper, &arg);
  96
  97         return arg.cnt != -1 ? arg.cnt : 0;
  98 }