libsanitizer/sanitizer_common/sanitizer_unwind_linux_libcdep.cpp

   1 //===-- sanitizer_unwind_linux_libcdep.cpp --------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file contains the unwind.h-based (aka "slow") stack unwinding routines
  10 // available to the tools on Linux, Android, NetBSD, FreeBSD, and Solaris.
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "sanitizer_platform.h"
  14 #if SANITIZER_FREEBSD || SANITIZER_LINUX || SANITIZER_NETBSD || \
  15     SANITIZER_SOLARIS
  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 namespace {
  31
  32 //---------------------------- UnwindSlow --------------------------------------
  33
  34 typedef struct {
  35   uptr absolute_pc;
  36   uptr stack_top;
  37   uptr stack_size;
  38 } backtrace_frame_t;
  39
  40 extern "C" {
  41 typedef void *(*acquire_my_map_info_list_func)();
  42 typedef void (*release_my_map_info_list_func)(void *map);
  43 typedef sptr (*unwind_backtrace_signal_arch_func)(
  44     void *siginfo, void *sigcontext, void *map_info_list,
  45     backtrace_frame_t *backtrace, uptr ignore_depth, uptr max_depth);
  46 acquire_my_map_info_list_func acquire_my_map_info_list;
  47 release_my_map_info_list_func release_my_map_info_list;
  48 unwind_backtrace_signal_arch_func unwind_backtrace_signal_arch;
  49 } // extern "C"
  50
  51 #if defined(__arm__) && !SANITIZER_NETBSD
  52 // NetBSD uses dwarf EH
  53 #define UNWIND_STOP _URC_END_OF_STACK
  54 #define UNWIND_CONTINUE _URC_NO_REASON
  55 #else
  56 #define UNWIND_STOP _URC_NORMAL_STOP
  57 #define UNWIND_CONTINUE _URC_NO_REASON
  58 #endif
  59
  60 uptr Unwind_GetIP(struct _Unwind_Context *ctx) {
  61 #if defined(__arm__) && !SANITIZER_APPLE
  62   uptr val;
  63   _Unwind_VRS_Result res = _Unwind_VRS_Get(ctx, _UVRSC_CORE,
  64       15 /* r15 = PC */, _UVRSD_UINT32, &val);
  65   CHECK(res == _UVRSR_OK && "_Unwind_VRS_Get failed");
  66   // Clear the Thumb bit.
  67   return val & ~(uptr)1;
  68 #else
  69   return (uptr)_Unwind_GetIP(ctx);
  70 #endif
  71 }
  72
  73 struct UnwindTraceArg {
  74   BufferedStackTrace *stack;
  75   u32 max_depth;
  76 };
  77
  78 _Unwind_Reason_Code Unwind_Trace(struct _Unwind_Context *ctx, void *param) {
  79   UnwindTraceArg *arg = (UnwindTraceArg*)param;
  80   CHECK_LT(arg->stack->size, arg->max_depth);
  81   uptr pc = Unwind_GetIP(ctx);
  82   const uptr kPageSize = GetPageSizeCached();
  83   // Let's assume that any pointer in the 0th page (i.e. <0x1000 on i386 and
  84   // x86_64) is invalid and stop unwinding here.  If we're adding support for
  85   // a platform where this isn't true, we need to reconsider this check.
  86   if (pc < kPageSize) return UNWIND_STOP;
  87   arg->stack->trace_buffer[arg->stack->size++] = pc;
  88   if (arg->stack->size == arg->max_depth) return UNWIND_STOP;
  89   return UNWIND_CONTINUE;
  90 }
  91
  92 }  // namespace
  93
  94 #if SANITIZER_ANDROID
  95 void SanitizerInitializeUnwinder() {
  96   if (AndroidGetApiLevel() >= ANDROID_LOLLIPOP_MR1) return;
  97
  98   // Pre-lollipop Android can not unwind through signal handler frames with
  99   // libgcc unwinder, but it has a libcorkscrew.so library with the necessary
 100   // workarounds.
 101   void *p = dlopen("libcorkscrew.so", RTLD_LAZY);
 102   if (!p) {
 103     VReport(1,
 104             "Failed to open libcorkscrew.so. You may see broken stack traces "
 105             "in SEGV reports.");
 106     return;
 107   }
 108   acquire_my_map_info_list =
 109       (acquire_my_map_info_list_func)(uptr)dlsym(p, "acquire_my_map_info_list");
 110   release_my_map_info_list =
 111       (release_my_map_info_list_func)(uptr)dlsym(p, "release_my_map_info_list");
 112   unwind_backtrace_signal_arch = (unwind_backtrace_signal_arch_func)(uptr)dlsym(
 113       p, "unwind_backtrace_signal_arch");
 114   if (!acquire_my_map_info_list || !release_my_map_info_list ||
 115       !unwind_backtrace_signal_arch) {
 116     VReport(1,
 117             "Failed to find one of the required symbols in libcorkscrew.so. "
 118             "You may see broken stack traces in SEGV reports.");
 119     acquire_my_map_info_list = 0;
 120     unwind_backtrace_signal_arch = 0;
 121     release_my_map_info_list = 0;
 122   }
 123 }
 124 #endif
 125
 126 void BufferedStackTrace::UnwindSlow(uptr pc, u32 max_depth) {
 127   CHECK_GE(max_depth, 2);
 128   size = 0;
 129   UnwindTraceArg arg = {this, Min(max_depth + 1, kStackTraceMax)};
 130   _Unwind_Backtrace(Unwind_Trace, &arg);
 131   // We need to pop a few frames so that pc is on top.
 132   uptr to_pop = LocatePcInTrace(pc);
 133   // trace_buffer[0] belongs to the current function so we always pop it,
 134   // unless there is only 1 frame in the stack trace (1 frame is always better
 135   // than 0!).
 136   // 1-frame stacks don't normally happen, but this depends on the actual
 137   // unwinder implementation (libgcc, libunwind, etc) which is outside of our
 138   // control.
 139   if (to_pop == 0 && size > 1)
 140     to_pop = 1;
 141   PopStackFrames(to_pop);
 142   trace_buffer[0] = pc;
 143 }
 144
 145 void BufferedStackTrace::UnwindSlow(uptr pc, void *context, u32 max_depth) {
 146   CHECK(context);
 147   CHECK_GE(max_depth, 2);
 148   if (!unwind_backtrace_signal_arch) {
 149     UnwindSlow(pc, max_depth);
 150     return;
 151   }
 152
 153   void *map = acquire_my_map_info_list();
 154   CHECK(map);
 155   InternalMmapVector<backtrace_frame_t> frames(kStackTraceMax);
 156   // siginfo argument appears to be unused.
 157   sptr res = unwind_backtrace_signal_arch(/* siginfo */ 0, context, map,
 158                                           frames.data(),
 159                                           /* ignore_depth */ 0, max_depth);
 160   release_my_map_info_list(map);
 161   if (res < 0) return;
 162   CHECK_LE((uptr)res, kStackTraceMax);
 163
 164   size = 0;
 165   // +2 compensate for libcorkscrew unwinder returning addresses of call
 166   // instructions instead of raw return addresses.
 167   for (sptr i = 0; i < res; ++i)
 168     trace_buffer[size++] = frames[i].absolute_pc + 2;
 169 }
 170
 171 }  // namespace __sanitizer
 172
 173 #endif  // SANITIZER_FREEBSD || SANITIZER_LINUX || SANITIZER_NETBSD ||
 174         // SANITIZER_SOLARIS