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   if (AndroidGetApiLevel() >= ANDROID_LOLLIPOP_MR1) return;
  50
  51   // Pre-lollipop Android can not unwind through signal handler frames with
  52   // libgcc unwinder, but it has a libcorkscrew.so library with the necessary
  53   // workarounds.
  54   void *p = dlopen("libcorkscrew.so", RTLD_LAZY);
  55   if (!p) {
  56     VReport(1,
  57             "Failed to open libcorkscrew.so. You may see broken stack traces "
  58             "in SEGV reports.");
  59     return;
  60   }
  61   acquire_my_map_info_list =
  62       (acquire_my_map_info_list_func)(uptr)dlsym(p, "acquire_my_map_info_list");
  63   release_my_map_info_list =
  64       (release_my_map_info_list_func)(uptr)dlsym(p, "release_my_map_info_list");
  65   unwind_backtrace_signal_arch = (unwind_backtrace_signal_arch_func)(uptr)dlsym(
  66       p, "unwind_backtrace_signal_arch");
  67   if (!acquire_my_map_info_list || !release_my_map_info_list ||
  68       !unwind_backtrace_signal_arch) {
  69     VReport(1,
  70             "Failed to find one of the required symbols in libcorkscrew.so. "
  71             "You may see broken stack traces in SEGV reports.");
  72     acquire_my_map_info_list = 0;
  73     unwind_backtrace_signal_arch = 0;
  74     release_my_map_info_list = 0;
  75   }
  76 }
  77 #endif
  78
  79 #ifdef __arm__
  80 #define UNWIND_STOP _URC_END_OF_STACK
  81 #define UNWIND_CONTINUE _URC_NO_REASON
  82 #else
  83 #define UNWIND_STOP _URC_NORMAL_STOP
  84 #define UNWIND_CONTINUE _URC_NO_REASON
  85 #endif
  86
  87 uptr Unwind_GetIP(struct _Unwind_Context *ctx) {
  88 #if defined(__arm__) && !SANITIZER_MAC
  89   uptr val;
  90   _Unwind_VRS_Result res = _Unwind_VRS_Get(ctx, _UVRSC_CORE,
  91       15 /* r15 = PC */, _UVRSD_UINT32, &val);
  92   CHECK(res == _UVRSR_OK && "_Unwind_VRS_Get failed");
  93   // Clear the Thumb bit.
  94   return val & ~(uptr)1;
  95 #else
  96   return _Unwind_GetIP(ctx);
  97 #endif
  98 }
  99
 100 struct UnwindTraceArg {
 101   BufferedStackTrace *stack;
 102   u32 max_depth;
 103 };
 104
 105 _Unwind_Reason_Code Unwind_Trace(struct _Unwind_Context *ctx, void *param) {
 106   UnwindTraceArg *arg = (UnwindTraceArg*)param;
 107   CHECK_LT(arg->stack->size, arg->max_depth);
 108   uptr pc = Unwind_GetIP(ctx);
 109   const uptr kPageSize = GetPageSizeCached();
 110   // Let's assume that any pointer in the 0th page (i.e. <0x1000 on i386 and
 111   // x86_64) is invalid and stop unwinding here.  If we're adding support for
 112   // a platform where this isn't true, we need to reconsider this check.
 113   if (pc < kPageSize) return UNWIND_STOP;
 114   arg->stack->trace_buffer[arg->stack->size++] = pc;
 115   if (arg->stack->size == arg->max_depth) return UNWIND_STOP;
 116   return UNWIND_CONTINUE;
 117 }
 118
 119 void BufferedStackTrace::SlowUnwindStack(uptr pc, u32 max_depth) {
 120   CHECK_GE(max_depth, 2);
 121   size = 0;
 122   UnwindTraceArg arg = {this, Min(max_depth + 1, kStackTraceMax)};
 123   _Unwind_Backtrace(Unwind_Trace, &arg);
 124   // We need to pop a few frames so that pc is on top.
 125   uptr to_pop = LocatePcInTrace(pc);
 126   // trace_buffer[0] belongs to the current function so we always pop it,
 127   // unless there is only 1 frame in the stack trace (1 frame is always better
 128   // than 0!).
 129   // 1-frame stacks don't normally happen, but this depends on the actual
 130   // unwinder implementation (libgcc, libunwind, etc) which is outside of our
 131   // control.
 132   if (to_pop == 0 && size > 1)
 133     to_pop = 1;
 134   PopStackFrames(to_pop);
 135   trace_buffer[0] = pc;
 136 }
 137
 138 void BufferedStackTrace::SlowUnwindStackWithContext(uptr pc, void *context,
 139                                                     u32 max_depth) {
 140   CHECK_GE(max_depth, 2);
 141   if (!unwind_backtrace_signal_arch) {
 142     SlowUnwindStack(pc, max_depth);
 143     return;
 144   }
 145
 146   void *map = acquire_my_map_info_list();
 147   CHECK(map);
 148   InternalScopedBuffer<backtrace_frame_t> frames(kStackTraceMax);
 149   // siginfo argument appears to be unused.
 150   sptr res = unwind_backtrace_signal_arch(/* siginfo */ 0, context, map,
 151                                           frames.data(),
 152                                           /* ignore_depth */ 0, max_depth);
 153   release_my_map_info_list(map);
 154   if (res < 0) return;
 155   CHECK_LE((uptr)res, kStackTraceMax);
 156
 157   size = 0;
 158   // +2 compensate for libcorkscrew unwinder returning addresses of call
 159   // instructions instead of raw return addresses.
 160   for (sptr i = 0; i < res; ++i)
 161     trace_buffer[size++] = frames[i].absolute_pc + 2;
 162 }
 163
 164 }  // namespace __sanitizer
 165
 166 #endif  // SANITIZER_FREEBSD || SANITIZER_LINUX