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