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
17namespace __sanitizer {
18
19uptr 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
29uptr StackTrace::GetCurrentPc() {
30  return GET_CALLER_PC();
31}
32
33void 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.
48static 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 LLVM.
64  return bp_prev;
65#else
66  return (uhwptr*)bp;
67#endif
68}
69
70void 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 at offset
88    // 16 of the *caller's* stack frame.  Thus we must dereference the
89    // back chain 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    uhwptr pc1 = caller_frame[2];
95#elif defined(__s390__)
96    uhwptr pc1 = frame[14];
97#else
98    uhwptr pc1 = frame[1];
99#endif
100    // Let's assume that any pointer in the 0th page (i.e. <0x1000 on i386 and
101    // x86_64) is invalid and stop unwinding here.  If we're adding support for
102    // a platform where this isn't true, we need to reconsider this check.
103    if (pc1 < kPageSize)
104      break;
105    if (pc1 != pc) {
106      trace_buffer[size++] = (uptr) pc1;
107    }
108    bottom = (uptr)frame;
109    frame = GetCanonicFrame((uptr)frame[0], stack_top, bottom);
110  }
111}
112
113#endif  // !defined(__sparc__)
114
115void BufferedStackTrace::PopStackFrames(uptr count) {
116  CHECK_LT(count, size);
117  size -= count;
118  for (uptr i = 0; i < size; ++i) {
119    trace_buffer[i] = trace_buffer[i + count];
120  }
121}
122
123static uptr Distance(uptr a, uptr b) { return a < b ? b - a : a - b; }
124
125uptr BufferedStackTrace::LocatePcInTrace(uptr pc) {
126  uptr best = 0;
127  for (uptr i = 1; i < size; ++i) {
128    if (Distance(trace[i], pc) < Distance(trace[best], pc)) best = i;
129  }
130  return best;
131}
132
133}  // namespace __sanitizer
134