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