libsanitizer/sanitizer_common/sanitizer_stacktrace.cpp

   1 //===-- sanitizer_stacktrace.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 is shared between AddressSanitizer and ThreadSanitizer
  10 // run-time libraries.
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "sanitizer_stacktrace.h"
  14
  15 #include "sanitizer_common.h"
  16 #include "sanitizer_flags.h"
  17 #include "sanitizer_platform.h"
  18 #include "sanitizer_ptrauth.h"
  19
  20 namespace __sanitizer {
  21
  22 uptr StackTrace::GetNextInstructionPc(uptr pc) {
  23 #if defined(__sparc__) || defined(__mips__)
  24   return pc + 8;
  25 #elif defined(__powerpc__) || defined(__arm__) || defined(__aarch64__)
  26   return pc + 4;
  27 #elif SANITIZER_RISCV64
  28   // Current check order is 4 -> 2 -> 6 -> 8
  29   u8 InsnByte = *(u8 *)(pc);
  30   if (((InsnByte & 0x3) == 0x3) && ((InsnByte & 0x1c) != 0x1c)) {
  31     // xxxxxxxxxxxbbb11 | 32 bit | bbb != 111
  32     return pc + 4;
  33   }
  34   if ((InsnByte & 0x3) != 0x3) {
  35     // xxxxxxxxxxxxxxaa | 16 bit | aa != 11
  36     return pc + 2;
  37   }
  38   // RISC-V encoding allows instructions to be up to 8 bytes long
  39   if ((InsnByte & 0x3f) == 0x1f) {
  40     // xxxxxxxxxx011111 | 48 bit |
  41     return pc + 6;
  42   }
  43   if ((InsnByte & 0x7f) == 0x3f) {
  44     // xxxxxxxxx0111111 | 64 bit |
  45     return pc + 8;
  46   }
  47   // bail-out if could not figure out the instruction size
  48   return 0;
  49 #else
  50   return pc + 1;
  51 #endif
  52 }
  53
  54 uptr StackTrace::GetCurrentPc() {
  55   return GET_CALLER_PC();
  56 }
  57
  58 void BufferedStackTrace::Init(const uptr *pcs, uptr cnt, uptr extra_top_pc) {
  59   size = cnt + !!extra_top_pc;
  60   CHECK_LE(size, kStackTraceMax);
  61   internal_memcpy(trace_buffer, pcs, cnt * sizeof(trace_buffer[0]));
  62   if (extra_top_pc)
  63     trace_buffer[cnt] = extra_top_pc;
  64   top_frame_bp = 0;
  65 }
  66
  67 // Sparc implemention is in its own file.
  68 #if !defined(__sparc__)
  69
  70 // In GCC on ARM bp points to saved lr, not fp, so we should check the next
  71 // cell in stack to be a saved frame pointer. GetCanonicFrame returns the
  72 // pointer to saved frame pointer in any case.
  73 static inline uhwptr *GetCanonicFrame(uptr bp,
  74                                       uptr stack_top,
  75                                       uptr stack_bottom) {
  76   CHECK_GT(stack_top, stack_bottom);
  77 #ifdef __arm__
  78   if (!IsValidFrame(bp, stack_top, stack_bottom)) return 0;
  79   uhwptr *bp_prev = (uhwptr *)bp;
  80   if (IsValidFrame((uptr)bp_prev[0], stack_top, stack_bottom)) return bp_prev;
  81   // The next frame pointer does not look right. This could be a GCC frame, step
  82   // back by 1 word and try again.
  83   if (IsValidFrame((uptr)bp_prev[-1], stack_top, stack_bottom))
  84     return bp_prev - 1;
  85   // Nope, this does not look right either. This means the frame after next does
  86   // not have a valid frame pointer, but we can still extract the caller PC.
  87   // Unfortunately, there is no way to decide between GCC and LLVM frame
  88   // layouts. Assume GCC.
  89   return bp_prev - 1;
  90 #else
  91   return (uhwptr*)bp;
  92 #endif
  93 }
  94
  95 void BufferedStackTrace::UnwindFast(uptr pc, uptr bp, uptr stack_top,
  96                                     uptr stack_bottom, u32 max_depth) {
  97   // TODO(yln): add arg sanity check for stack_top/stack_bottom
  98   CHECK_GE(max_depth, 2);
  99   const uptr kPageSize = GetPageSizeCached();
 100   trace_buffer[0] = pc;
 101   size = 1;
 102   if (stack_top < 4096) return;  // Sanity check for stack top.
 103   uhwptr *frame = GetCanonicFrame(bp, stack_top, stack_bottom);
 104   // Lowest possible address that makes sense as the next frame pointer.
 105   // Goes up as we walk the stack.
 106   uptr bottom = stack_bottom;
 107   // Avoid infinite loop when frame == frame[0] by using frame > prev_frame.
 108   while (IsValidFrame((uptr)frame, stack_top, bottom) &&
 109          IsAligned((uptr)frame, sizeof(*frame)) &&
 110          size < max_depth) {
 111 #ifdef __powerpc__
 112     // PowerPC ABIs specify that the return address is saved on the
 113     // *caller's* stack frame.  Thus we must dereference the back chain
 114     // to find the caller frame before extracting it.
 115     uhwptr *caller_frame = (uhwptr*)frame[0];
 116     if (!IsValidFrame((uptr)caller_frame, stack_top, bottom) ||
 117         !IsAligned((uptr)caller_frame, sizeof(uhwptr)))
 118       break;
 119     // For most ABIs the offset where the return address is saved is two
 120     // register sizes.  The exception is the SVR4 ABI, which uses an
 121     // offset of only one register size.
 122 #ifdef _CALL_SYSV
 123     uhwptr pc1 = caller_frame[1];
 124 #else
 125     uhwptr pc1 = caller_frame[2];
 126 #endif
 127 #elif defined(__s390__)
 128     uhwptr pc1 = frame[14];
 129 #elif defined(__riscv)
 130     // frame[-1] contains the return address
 131     uhwptr pc1 = frame[-1];
 132 #else
 133     uhwptr pc1 = STRIP_PAC_PC((void *)frame[1]);
 134 #endif
 135     // Let's assume that any pointer in the 0th page (i.e. <0x1000 on i386 and
 136     // x86_64) is invalid and stop unwinding here.  If we're adding support for
 137     // a platform where this isn't true, we need to reconsider this check.
 138     if (pc1 < kPageSize)
 139       break;
 140     if (pc1 != pc) {
 141       trace_buffer[size++] = (uptr) pc1;
 142     }
 143     bottom = (uptr)frame;
 144 #if defined(__riscv)
 145     // frame[-2] contain fp of the previous frame
 146     uptr new_bp = (uptr)frame[-2];
 147 #else
 148     uptr new_bp = (uptr)frame[0];
 149 #endif
 150     frame = GetCanonicFrame(new_bp, stack_top, bottom);
 151   }
 152 }
 153
 154 #endif  // !defined(__sparc__)
 155
 156 void BufferedStackTrace::PopStackFrames(uptr count) {
 157   CHECK_LT(count, size);
 158   size -= count;
 159   for (uptr i = 0; i < size; ++i) {
 160     trace_buffer[i] = trace_buffer[i + count];
 161   }
 162 }
 163
 164 static uptr Distance(uptr a, uptr b) { return a < b ? b - a : a - b; }
 165
 166 uptr BufferedStackTrace::LocatePcInTrace(uptr pc) {
 167   uptr best = 0;
 168   for (uptr i = 1; i < size; ++i) {
 169     if (Distance(trace[i], pc) < Distance(trace[best], pc)) best = i;
 170   }
 171   return best;
 172 }
 173
 174 }  // namespace __sanitizer