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
backtrace_init(void)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
unwind_getgr(_Unwind_Context * context,int regno)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
backtrace_helper(struct _Unwind_Context * ctx,void * a)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 */
backtrace(void ** array,int size)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 }
99