1 //===-- sanitizer_unwind_posix.cc ----------------------------------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file contains the unwind.h-based (aka "slow") stack unwinding routines
11 // available to the tools on Linux, Android, FreeBSD and OS X.
12 //===----------------------------------------------------------------------===//
13
14 #include "sanitizer_platform.h"
15 #if SANITIZER_POSIX
16 #include "sanitizer_common.h"
17 #include "sanitizer_stacktrace.h"
18
19 #if SANITIZER_ANDROID
20 #include <dlfcn.h> // for dlopen()
21 #endif
22
23 #if SANITIZER_FREEBSD
24 #define _GNU_SOURCE // to declare _Unwind_Backtrace() from <unwind.h>
25 #endif
26 #include <unwind.h>
27
28 namespace __sanitizer {
29
30 //------------------------- SlowUnwindStack -----------------------------------
31
32 typedef struct {
33 uptr absolute_pc;
34 uptr stack_top;
35 uptr stack_size;
36 } backtrace_frame_t;
37
38 extern "C" {
39 typedef void *(*acquire_my_map_info_list_func)();
40 typedef void (*release_my_map_info_list_func)(void *map);
41 typedef sptr (*unwind_backtrace_signal_arch_func)(
42 void *siginfo, void *sigcontext, void *map_info_list,
43 backtrace_frame_t *backtrace, uptr ignore_depth, uptr max_depth);
44 acquire_my_map_info_list_func acquire_my_map_info_list;
45 release_my_map_info_list_func release_my_map_info_list;
46 unwind_backtrace_signal_arch_func unwind_backtrace_signal_arch;
47 } // extern "C"
48
49 #if SANITIZER_ANDROID
SanitizerInitializeUnwinder()50 void SanitizerInitializeUnwinder() {
51 void *p = dlopen("libcorkscrew.so", RTLD_LAZY);
52 if (!p) {
53 VReport(1,
54 "Failed to open libcorkscrew.so. You may see broken stack traces "
55 "in SEGV reports.");
56 return;
57 }
58 acquire_my_map_info_list =
59 (acquire_my_map_info_list_func)(uptr)dlsym(p, "acquire_my_map_info_list");
60 release_my_map_info_list =
61 (release_my_map_info_list_func)(uptr)dlsym(p, "release_my_map_info_list");
62 unwind_backtrace_signal_arch = (unwind_backtrace_signal_arch_func)(uptr)dlsym(
63 p, "unwind_backtrace_signal_arch");
64 if (!acquire_my_map_info_list || !release_my_map_info_list ||
65 !unwind_backtrace_signal_arch) {
66 VReport(1,
67 "Failed to find one of the required symbols in libcorkscrew.so. "
68 "You may see broken stack traces in SEGV reports.");
69 acquire_my_map_info_list = 0;
70 unwind_backtrace_signal_arch = 0;
71 release_my_map_info_list = 0;
72 }
73 }
74 #endif
75
76 #ifdef __arm__
77 #define UNWIND_STOP _URC_END_OF_STACK
78 #define UNWIND_CONTINUE _URC_NO_REASON
79 #else
80 #define UNWIND_STOP _URC_NORMAL_STOP
81 #define UNWIND_CONTINUE _URC_NO_REASON
82 #endif
83
Unwind_GetIP(struct _Unwind_Context * ctx)84 uptr Unwind_GetIP(struct _Unwind_Context *ctx) {
85 #ifdef __arm__
86 uptr val;
87 _Unwind_VRS_Result res = _Unwind_VRS_Get(ctx, _UVRSC_CORE,
88 15 /* r15 = PC */, _UVRSD_UINT32, &val);
89 CHECK(res == _UVRSR_OK && "_Unwind_VRS_Get failed");
90 // Clear the Thumb bit.
91 return val & ~(uptr)1;
92 #else
93 return _Unwind_GetIP(ctx);
94 #endif
95 }
96
97 struct UnwindTraceArg {
98 BufferedStackTrace *stack;
99 u32 max_depth;
100 };
101
Unwind_Trace(struct _Unwind_Context * ctx,void * param)102 _Unwind_Reason_Code Unwind_Trace(struct _Unwind_Context *ctx, void *param) {
103 UnwindTraceArg *arg = (UnwindTraceArg*)param;
104 CHECK_LT(arg->stack->size, arg->max_depth);
105 uptr pc = Unwind_GetIP(ctx);
106 arg->stack->trace_buffer[arg->stack->size++] = pc;
107 if (arg->stack->size == arg->max_depth) return UNWIND_STOP;
108 return UNWIND_CONTINUE;
109 }
110
SlowUnwindStack(uptr pc,u32 max_depth)111 void BufferedStackTrace::SlowUnwindStack(uptr pc, u32 max_depth) {
112 CHECK_GE(max_depth, 2);
113 size = 0;
114 UnwindTraceArg arg = {this, Min(max_depth + 1, kStackTraceMax)};
115 _Unwind_Backtrace(Unwind_Trace, &arg);
116 // We need to pop a few frames so that pc is on top.
117 uptr to_pop = LocatePcInTrace(pc);
118 // trace_buffer[0] belongs to the current function so we always pop it,
119 // unless there is only 1 frame in the stack trace (1 frame is always better
120 // than 0!).
121 // 1-frame stacks don't normally happen, but this depends on the actual
122 // unwinder implementation (libgcc, libunwind, etc) which is outside of our
123 // control.
124 if (to_pop == 0 && size > 1)
125 to_pop = 1;
126 PopStackFrames(to_pop);
127 trace_buffer[0] = pc;
128 }
129
SlowUnwindStackWithContext(uptr pc,void * context,u32 max_depth)130 void BufferedStackTrace::SlowUnwindStackWithContext(uptr pc, void *context,
131 u32 max_depth) {
132 CHECK_GE(max_depth, 2);
133 if (!unwind_backtrace_signal_arch) {
134 SlowUnwindStack(pc, max_depth);
135 return;
136 }
137
138 void *map = acquire_my_map_info_list();
139 CHECK(map);
140 InternalScopedBuffer<backtrace_frame_t> frames(kStackTraceMax);
141 // siginfo argument appears to be unused.
142 sptr res = unwind_backtrace_signal_arch(/* siginfo */ 0, context, map,
143 frames.data(),
144 /* ignore_depth */ 0, max_depth);
145 release_my_map_info_list(map);
146 if (res < 0) return;
147 CHECK_LE((uptr)res, kStackTraceMax);
148
149 size = 0;
150 // +2 compensate for libcorkscrew unwinder returning addresses of call
151 // instructions instead of raw return addresses.
152 for (sptr i = 0; i < res; ++i)
153 trace_buffer[size++] = frames[i].absolute_pc + 2;
154 }
155
156 } // namespace __sanitizer
157
158 #endif // SANITIZER_POSIX
159