libsanitizer/sanitizer_common/sanitizer_unwind_linux_libcdep.cc

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