llvm-project

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(__loongarch__) || 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(__loongarch__) || 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
170