compiler-rt/lib/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(__aarch64__)
  24   return STRIP_PAC_PC((void *)pc) + 4;
  25 #elif defined(__sparc__) || defined(__mips__)
  26   return pc + 8;
  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 #elif SANITIZER_S390 || SANITIZER_I386 || SANITIZER_X32 || SANITIZER_X64
  50   return pc + 1;
  51 #else
  52   return pc + 4;
  53 #endif
  54 }
  55
  56 uptr StackTrace::GetCurrentPc() {
  57   return GET_CALLER_PC();
  58 }
  59
  60 void BufferedStackTrace::Init(const uptr *pcs, uptr cnt, uptr extra_top_pc) {
  61   size = cnt + !!extra_top_pc;
  62   CHECK_LE(size, kStackTraceMax);
  63   internal_memcpy(trace_buffer, pcs, cnt * sizeof(trace_buffer[0]));
  64   if (extra_top_pc)
  65     trace_buffer[cnt] = extra_top_pc;
  66   top_frame_bp = 0;
  67 }
  68
  69 // Sparc implementation is in its own file.
  70 #if !defined(__sparc__)
  71
  72 // In GCC on ARM bp points to saved lr, not fp, so we should check the next
  73 // cell in stack to be a saved frame pointer. GetCanonicFrame returns the
  74 // pointer to saved frame pointer in any case.
  75 static inline uhwptr *GetCanonicFrame(uptr bp,
  76                                       uptr stack_top,
  77                                       uptr stack_bottom) {
  78   CHECK_GT(stack_top, stack_bottom);
  79 #ifdef __arm__
  80   if (!IsValidFrame(bp, stack_top, stack_bottom)) return 0;
  81   uhwptr *bp_prev = (uhwptr *)bp;
  82   if (IsValidFrame((uptr)bp_prev[0], stack_top, stack_bottom)) return bp_prev;
  83   // The next frame pointer does not look right. This could be a GCC frame, step
  84   // back by 1 word and try again.
  85   if (IsValidFrame((uptr)bp_prev[-1], stack_top, stack_bottom))
  86     return bp_prev - 1;
  87   // Nope, this does not look right either. This means the frame after next does
  88   // not have a valid frame pointer, but we can still extract the caller PC.
  89   // Unfortunately, there is no way to decide between GCC and LLVM frame
  90   // layouts. Assume LLVM.
  91   return bp_prev;
  92 #else
  93   return (uhwptr*)bp;
  94 #endif
  95 }
  96
  97 void BufferedStackTrace::UnwindFast(uptr pc, uptr bp, uptr stack_top,
  98                                     uptr stack_bottom, u32 max_depth) {
  99   // TODO(yln): add arg sanity check for stack_top/stack_bottom
 100   CHECK_GE(max_depth, 2);
 101   const uptr kPageSize = GetPageSizeCached();
 102   trace_buffer[0] = pc;
 103   size = 1;
 104   if (stack_top < 4096) return;  // Sanity check for stack top.
 105   uhwptr *frame = GetCanonicFrame(bp, stack_top, stack_bottom);
 106   // Lowest possible address that makes sense as the next frame pointer.
 107   // Goes up as we walk the stack.
 108   uptr bottom = stack_bottom;
 109   // Avoid infinite loop when frame == frame[0] by using frame > prev_frame.
 110   while (IsValidFrame((uptr)frame, stack_top, bottom) &&
 111          IsAligned((uptr)frame, sizeof(*frame)) &&
 112          size < max_depth) {
 113 #ifdef __powerpc__
 114     // PowerPC ABIs specify that the return address is saved at offset
 115     // 16 of the *caller's* stack frame.  Thus we must dereference the
 116     // back chain to find the caller frame before extracting it.
 117     uhwptr *caller_frame = (uhwptr*)frame[0];
 118     if (!IsValidFrame((uptr)caller_frame, stack_top, bottom) ||
 119         !IsAligned((uptr)caller_frame, sizeof(uhwptr)))
 120       break;
 121     uhwptr pc1 = caller_frame[2];
 122 #elif defined(__s390__)
 123     uhwptr pc1 = frame[14];
 124 #elif defined(__riscv)
 125     // frame[-1] contains the return address
 126     uhwptr pc1 = frame[-1];
 127 #else
 128     uhwptr pc1 = STRIP_PAC_PC((void *)frame[1]);
 129 #endif
 130     // Let's assume that any pointer in the 0th page (i.e. <0x1000 on i386 and
 131     // x86_64) is invalid and stop unwinding here.  If we're adding support for
 132     // a platform where this isn't true, we need to reconsider this check.
 133     if (pc1 < kPageSize)
 134       break;
 135     if (pc1 != pc) {
 136       trace_buffer[size++] = (uptr) pc1;
 137     }
 138     bottom = (uptr)frame;
 139 #if defined(__riscv)
 140     // frame[-2] contain fp of the previous frame
 141     uptr new_bp = (uptr)frame[-2];
 142 #else
 143     uptr new_bp = (uptr)frame[0];
 144 #endif
 145     frame = GetCanonicFrame(new_bp, stack_top, bottom);
 146   }
 147 }
 148
 149 #endif  // !defined(__sparc__)
 150
 151 void BufferedStackTrace::PopStackFrames(uptr count) {
 152   CHECK_LT(count, size);
 153   size -= count;
 154   for (uptr i = 0; i < size; ++i) {
 155     trace_buffer[i] = trace_buffer[i + count];
 156   }
 157 }
 158
 159 static uptr Distance(uptr a, uptr b) { return a < b ? b - a : a - b; }
 160
 161 uptr BufferedStackTrace::LocatePcInTrace(uptr pc) {
 162   uptr best = 0;
 163   for (uptr i = 1; i < size; ++i) {
 164     if (Distance(trace[i], pc) < Distance(trace[best], pc)) best = i;
 165   }
 166   return best;
 167 }
 168
 169 }  // namespace __sanitizer