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, NetBSD and FreeBSD.
  10 //===----------------------------------------------------------------------===//
  11
  12 #include "sanitizer_platform.h"
  13 #if SANITIZER_FREEBSD || SANITIZER_LINUX || SANITIZER_NETBSD
  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 #if defined(__arm__) && !SANITIZER_NETBSD
  80 // NetBSD uses dwarf EH
  81 #define UNWIND_STOP _URC_END_OF_STACK
  82 #define UNWIND_CONTINUE _URC_NO_REASON
  83 #else
  84 #define UNWIND_STOP _URC_NORMAL_STOP
  85 #define UNWIND_CONTINUE _URC_NO_REASON
  86 #endif
  87
  88 uptr Unwind_GetIP(struct _Unwind_Context *ctx) {
  89 #if defined(__arm__) && !SANITIZER_MAC
  90   uptr val;
  91   _Unwind_VRS_Result res = _Unwind_VRS_Get(ctx, _UVRSC_CORE,
  92       15 /* r15 = PC */, _UVRSD_UINT32, &val);
  93   CHECK(res == _UVRSR_OK && "_Unwind_VRS_Get failed");
  94   // Clear the Thumb bit.
  95   return val & ~(uptr)1;
  96 #else
  97   return _Unwind_GetIP(ctx);
  98 #endif
  99 }
 100
 101 struct UnwindTraceArg {
 102   BufferedStackTrace *stack;
 103   u32 max_depth;
 104 };
 105
 106 _Unwind_Reason_Code Unwind_Trace(struct _Unwind_Context *ctx, void *param) {
 107   UnwindTraceArg *arg = (UnwindTraceArg*)param;
 108   CHECK_LT(arg->stack->size, arg->max_depth);
 109   uptr pc = Unwind_GetIP(ctx);
 110   const uptr kPageSize = GetPageSizeCached();
 111   // Let's assume that any pointer in the 0th page (i.e. <0x1000 on i386 and
 112   // x86_64) is invalid and stop unwinding here.  If we're adding support for
 113   // a platform where this isn't true, we need to reconsider this check.
 114   if (pc < kPageSize) return UNWIND_STOP;
 115   arg->stack->trace_buffer[arg->stack->size++] = pc;
 116   if (arg->stack->size == arg->max_depth) return UNWIND_STOP;
 117   return UNWIND_CONTINUE;
 118 }
 119
 120 void BufferedStackTrace::SlowUnwindStack(uptr pc, u32 max_depth) {
 121   CHECK_GE(max_depth, 2);
 122   size = 0;
 123   UnwindTraceArg arg = {this, Min(max_depth + 1, kStackTraceMax)};
 124   _Unwind_Backtrace(Unwind_Trace, &arg);
 125   // We need to pop a few frames so that pc is on top.
 126   uptr to_pop = LocatePcInTrace(pc);
 127   // trace_buffer[0] belongs to the current function so we always pop it,
 128   // unless there is only 1 frame in the stack trace (1 frame is always better
 129   // than 0!).
 130   // 1-frame stacks don't normally happen, but this depends on the actual
 131   // unwinder implementation (libgcc, libunwind, etc) which is outside of our
 132   // control.
 133   if (to_pop == 0 && size > 1)
 134     to_pop = 1;
 135   PopStackFrames(to_pop);
 136   trace_buffer[0] = pc;
 137 }
 138
 139 void BufferedStackTrace::SlowUnwindStackWithContext(uptr pc, void *context,
 140                                                     u32 max_depth) {
 141   CHECK_GE(max_depth, 2);
 142   if (!unwind_backtrace_signal_arch) {
 143     SlowUnwindStack(pc, max_depth);
 144     return;
 145   }
 146
 147   void *map = acquire_my_map_info_list();
 148   CHECK(map);
 149   InternalScopedBuffer<backtrace_frame_t> frames(kStackTraceMax);
 150   // siginfo argument appears to be unused.
 151   sptr res = unwind_backtrace_signal_arch(/* siginfo */ 0, context, map,
 152                                           frames.data(),
 153                                           /* ignore_depth */ 0, max_depth);
 154   release_my_map_info_list(map);
 155   if (res < 0) return;
 156   CHECK_LE((uptr)res, kStackTraceMax);
 157
 158   size = 0;
 159   // +2 compensate for libcorkscrew unwinder returning addresses of call
 160   // instructions instead of raw return addresses.
 161   for (sptr i = 0; i < res; ++i)
 162     trace_buffer[size++] = frames[i].absolute_pc + 2;
 163 }
 164
 165 }  // namespace __sanitizer
 166
 167 #endif  // SANITIZER_FREEBSD || SANITIZER_LINUX || SANITIZER_NETBSD