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 //---------------------------- UnwindSlow --------------------------------------
  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
  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 #if defined(__arm__) && !SANITIZER_NETBSD
  82 // NetBSD uses dwarf EH
  83 #define UNWIND_STOP _URC_END_OF_STACK
  84 #define UNWIND_CONTINUE _URC_NO_REASON
  85 #else
  86 #define UNWIND_STOP _URC_NORMAL_STOP
  87 #define UNWIND_CONTINUE _URC_NO_REASON
  88 #endif
  89
  90 uptr Unwind_GetIP(struct _Unwind_Context *ctx) {
  91 #if defined(__arm__) && !SANITIZER_MAC
  92   uptr val;
  93   _Unwind_VRS_Result res = _Unwind_VRS_Get(ctx, _UVRSC_CORE,
  94       15 /* r15 = PC */, _UVRSD_UINT32, &val);
  95   CHECK(res == _UVRSR_OK && "_Unwind_VRS_Get failed");
  96   // Clear the Thumb bit.
  97   return val & ~(uptr)1;
  98 #else
  99   return (uptr)_Unwind_GetIP(ctx);
 100 #endif
 101 }
 102
 103 struct UnwindTraceArg {
 104   BufferedStackTrace *stack;
 105   u32 max_depth;
 106 };
 107
 108 _Unwind_Reason_Code Unwind_Trace(struct _Unwind_Context *ctx, void *param) {
 109   UnwindTraceArg *arg = (UnwindTraceArg*)param;
 110   CHECK_LT(arg->stack->size, arg->max_depth);
 111   uptr pc = Unwind_GetIP(ctx);
 112   const uptr kPageSize = GetPageSizeCached();
 113   // Let's assume that any pointer in the 0th page (i.e. <0x1000 on i386 and
 114   // x86_64) is invalid and stop unwinding here.  If we're adding support for
 115   // a platform where this isn't true, we need to reconsider this check.
 116   if (pc < kPageSize) return UNWIND_STOP;
 117   arg->stack->trace_buffer[arg->stack->size++] = pc;
 118   if (arg->stack->size == arg->max_depth) return UNWIND_STOP;
 119   return UNWIND_CONTINUE;
 120 }
 121
 122 void BufferedStackTrace::UnwindSlow(uptr pc, u32 max_depth) {
 123   CHECK_GE(max_depth, 2);
 124   size = 0;
 125   UnwindTraceArg arg = {this, Min(max_depth + 1, kStackTraceMax)};
 126   _Unwind_Backtrace(Unwind_Trace, &arg);
 127   // We need to pop a few frames so that pc is on top.
 128   uptr to_pop = LocatePcInTrace(pc);
 129   // trace_buffer[0] belongs to the current function so we always pop it,
 130   // unless there is only 1 frame in the stack trace (1 frame is always better
 131   // than 0!).
 132   // 1-frame stacks don't normally happen, but this depends on the actual
 133   // unwinder implementation (libgcc, libunwind, etc) which is outside of our
 134   // control.
 135   if (to_pop == 0 && size > 1)
 136     to_pop = 1;
 137   PopStackFrames(to_pop);
 138 #if defined(__GNUC__) && defined(__sparc__)
 139   // __builtin_return_address returns the address of the call instruction
 140   // on the SPARC and not the return address, so we need to compensate.
 141   trace_buffer[0] = GetNextInstructionPc(pc);
 142 #else
 143   trace_buffer[0] = pc;
 144 #endif
 145 }
 146
 147 void BufferedStackTrace::UnwindSlow(uptr pc, void *context, u32 max_depth) {
 148   CHECK(context);
 149   CHECK_GE(max_depth, 2);
 150   if (!unwind_backtrace_signal_arch) {
 151     UnwindSlow(pc, max_depth);
 152     return;
 153   }
 154
 155   void *map = acquire_my_map_info_list();
 156   CHECK(map);
 157   InternalMmapVector<backtrace_frame_t> frames(kStackTraceMax);
 158   // siginfo argument appears to be unused.
 159   sptr res = unwind_backtrace_signal_arch(/* siginfo */ 0, context, map,
 160                                           frames.data(),
 161                                           /* ignore_depth */ 0, max_depth);
 162   release_my_map_info_list(map);
 163   if (res < 0) return;
 164   CHECK_LE((uptr)res, kStackTraceMax);
 165
 166   size = 0;
 167   // +2 compensate for libcorkscrew unwinder returning addresses of call
 168   // instructions instead of raw return addresses.
 169   for (sptr i = 0; i < res; ++i)
 170     trace_buffer[size++] = frames[i].absolute_pc + 2;
 171 }
 172
 173 }  // namespace __sanitizer
 174
 175 #endif  // SANITIZER_FREEBSD || SANITIZER_LINUX || SANITIZER_NETBSD ||
 176         // SANITIZER_SOLARIS