1 //===-- sanitizer_stacktrace.cc -------------------------------------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file is shared between AddressSanitizer and ThreadSanitizer
11 // run-time libraries.
12 //===----------------------------------------------------------------------===//
13
14 #include "sanitizer_common.h"
15 #include "sanitizer_flags.h"
16 #include "sanitizer_stacktrace.h"
17
18 namespace __sanitizer {
19
GetNextInstructionPc(uptr pc)20 uptr StackTrace::GetNextInstructionPc(uptr pc) {
21 #if defined(__mips__)
22 return pc + 8;
23 #elif defined(__powerpc__) || defined(__sparc__) || defined(__arm__) || \
24 defined(__aarch64__)
25 return pc + 4;
26 #else
27 return pc + 1;
28 #endif
29 }
30
GetCurrentPc()31 uptr StackTrace::GetCurrentPc() {
32 return GET_CALLER_PC();
33 }
34
Init(const uptr * pcs,uptr cnt,uptr extra_top_pc)35 void BufferedStackTrace::Init(const uptr *pcs, uptr cnt, uptr extra_top_pc) {
36 size = cnt + !!extra_top_pc;
37 CHECK_LE(size, kStackTraceMax);
38 internal_memcpy(trace_buffer, pcs, cnt * sizeof(trace_buffer[0]));
39 if (extra_top_pc)
40 trace_buffer[cnt] = extra_top_pc;
41 top_frame_bp = 0;
42 }
43
44 // Sparc implemention is in its own file.
45 #if !defined(__sparc__)
46
47 // In GCC on ARM bp points to saved lr, not fp, so we should check the next
48 // cell in stack to be a saved frame pointer. GetCanonicFrame returns the
49 // pointer to saved frame pointer in any case.
GetCanonicFrame(uptr bp,uptr stack_top,uptr stack_bottom)50 static inline uhwptr *GetCanonicFrame(uptr bp,
51 uptr stack_top,
52 uptr stack_bottom) {
53 #ifdef __arm__
54 if (!IsValidFrame(bp, stack_top, stack_bottom)) return 0;
55 uhwptr *bp_prev = (uhwptr *)bp;
56 if (IsValidFrame((uptr)bp_prev[0], stack_top, stack_bottom)) return bp_prev;
57 // The next frame pointer does not look right. This could be a GCC frame, step
58 // back by 1 word and try again.
59 if (IsValidFrame((uptr)bp_prev[-1], stack_top, stack_bottom))
60 return bp_prev - 1;
61 // Nope, this does not look right either. This means the frame after next does
62 // not have a valid frame pointer, but we can still extract the caller PC.
63 // Unfortunately, there is no way to decide between GCC and LLVM frame
64 // layouts. Assume LLVM.
65 return bp_prev;
66 #else
67 return (uhwptr*)bp;
68 #endif
69 }
70
FastUnwindStack(uptr pc,uptr bp,uptr stack_top,uptr stack_bottom,u32 max_depth)71 void BufferedStackTrace::FastUnwindStack(uptr pc, uptr bp, uptr stack_top,
72 uptr stack_bottom, u32 max_depth) {
73 const uptr kPageSize = GetPageSizeCached();
74 CHECK_GE(max_depth, 2);
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
PopStackFrames(uptr count)115 void 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
Distance(uptr a,uptr b)123 static uptr Distance(uptr a, uptr b) { return a < b ? b - a : a - b; }
124
LocatePcInTrace(uptr pc)125 uptr 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