1 //===-- sanitizer_unwind_linux_libcdep.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, and FreeBSD.
12 //===----------------------------------------------------------------------===//
13
14 #include "sanitizer_platform.h"
15 #if SANITIZER_FREEBSD || SANITIZER_LINUX
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 if (AndroidGetApiLevel() >= ANDROID_LOLLIPOP_MR1) return;
52
53 // Pre-lollipop Android can not unwind through signal handler frames with
54 // libgcc unwinder, but it has a libcorkscrew.so library with the necessary
55 // workarounds.
56 void *p = dlopen("libcorkscrew.so", RTLD_LAZY);
57 if (!p) {
58 VReport(1,
59 "Failed to open libcorkscrew.so. You may see broken stack traces "
60 "in SEGV reports.");
61 return;
62 }
63 acquire_my_map_info_list =
64 (acquire_my_map_info_list_func)(uptr)dlsym(p, "acquire_my_map_info_list");
65 release_my_map_info_list =
66 (release_my_map_info_list_func)(uptr)dlsym(p, "release_my_map_info_list");
67 unwind_backtrace_signal_arch = (unwind_backtrace_signal_arch_func)(uptr)dlsym(
68 p, "unwind_backtrace_signal_arch");
69 if (!acquire_my_map_info_list || !release_my_map_info_list ||
70 !unwind_backtrace_signal_arch) {
71 VReport(1,
72 "Failed to find one of the required symbols in libcorkscrew.so. "
73 "You may see broken stack traces in SEGV reports.");
74 acquire_my_map_info_list = 0;
75 unwind_backtrace_signal_arch = 0;
76 release_my_map_info_list = 0;
77 }
78 }
79 #endif
80
81 #ifdef __arm__
82 #define UNWIND_STOP _URC_END_OF_STACK
83 #define UNWIND_CONTINUE _URC_NO_REASON
84 #else
85 #define UNWIND_STOP _URC_NORMAL_STOP
86 #define UNWIND_CONTINUE _URC_NO_REASON
87 #endif
88
Unwind_GetIP(struct _Unwind_Context * ctx)89 uptr Unwind_GetIP(struct _Unwind_Context *ctx) {
90 #if defined(__arm__) && !SANITIZER_MAC
91 uptr val;
92 _Unwind_VRS_Result res = _Unwind_VRS_Get(ctx, _UVRSC_CORE,
93 15 /* r15 = PC */, _UVRSD_UINT32, &val);
94 CHECK(res == _UVRSR_OK && "_Unwind_VRS_Get failed");
95 // Clear the Thumb bit.
96 return val & ~(uptr)1;
97 #else
98 return _Unwind_GetIP(ctx);
99 #endif
100 }
101
102 struct UnwindTraceArg {
103 BufferedStackTrace *stack;
104 u32 max_depth;
105 };
106
Unwind_Trace(struct _Unwind_Context * ctx,void * param)107 _Unwind_Reason_Code Unwind_Trace(struct _Unwind_Context *ctx, void *param) {
108 UnwindTraceArg *arg = (UnwindTraceArg*)param;
109 CHECK_LT(arg->stack->size, arg->max_depth);
110 uptr pc = Unwind_GetIP(ctx);
111 const uptr kPageSize = GetPageSizeCached();
112 // Let's assume that any pointer in the 0th page (i.e. <0x1000 on i386 and
113 // x86_64) is invalid and stop unwinding here. If we're adding support for
114 // a platform where this isn't true, we need to reconsider this check.
115 if (pc < kPageSize) return UNWIND_STOP;
116 arg->stack->trace_buffer[arg->stack->size++] = pc;
117 if (arg->stack->size == arg->max_depth) return UNWIND_STOP;
118 return UNWIND_CONTINUE;
119 }
120
SlowUnwindStack(uptr pc,u32 max_depth)121 void BufferedStackTrace::SlowUnwindStack(uptr pc, u32 max_depth) {
122 CHECK_GE(max_depth, 2);
123 size = 0;
124 UnwindTraceArg arg = {this, Min(max_depth + 1, kStackTraceMax)};
125 _Unwind_Backtrace(Unwind_Trace, &arg);
126 // We need to pop a few frames so that pc is on top.
127 uptr to_pop = LocatePcInTrace(pc);
128 // trace_buffer[0] belongs to the current function so we always pop it,
129 // unless there is only 1 frame in the stack trace (1 frame is always better
130 // than 0!).
131 // 1-frame stacks don't normally happen, but this depends on the actual
132 // unwinder implementation (libgcc, libunwind, etc) which is outside of our
133 // control.
134 if (to_pop == 0 && size > 1)
135 to_pop = 1;
136 PopStackFrames(to_pop);
137 trace_buffer[0] = pc;
138 }
139
SlowUnwindStackWithContext(uptr pc,void * context,u32 max_depth)140 void BufferedStackTrace::SlowUnwindStackWithContext(uptr pc, void *context,
141 u32 max_depth) {
142 CHECK_GE(max_depth, 2);
143 if (!unwind_backtrace_signal_arch) {
144 SlowUnwindStack(pc, max_depth);
145 return;
146 }
147
148 void *map = acquire_my_map_info_list();
149 CHECK(map);
150 InternalScopedBuffer<backtrace_frame_t> frames(kStackTraceMax);
151 // siginfo argument appears to be unused.
152 sptr res = unwind_backtrace_signal_arch(/* siginfo */ 0, context, map,
153 frames.data(),
154 /* ignore_depth */ 0, max_depth);
155 release_my_map_info_list(map);
156 if (res < 0) return;
157 CHECK_LE((uptr)res, kStackTraceMax);
158
159 size = 0;
160 // +2 compensate for libcorkscrew unwinder returning addresses of call
161 // instructions instead of raw return addresses.
162 for (sptr i = 0; i < res; ++i)
163 trace_buffer[size++] = frames[i].absolute_pc + 2;
164 }
165
166 } // namespace __sanitizer
167
168 #endif // SANITIZER_FREEBSD || SANITIZER_LINUX
169