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__)
24 return pc + 4;
25 #else
26 return pc + 1;
27 #endif
28 }
29
GetCurrentPc()30 uptr StackTrace::GetCurrentPc() {
31 return GET_CALLER_PC();
32 }
33
Init(const uptr * pcs,uptr cnt,uptr extra_top_pc)34 void BufferedStackTrace::Init(const uptr *pcs, uptr cnt, uptr extra_top_pc) {
35 size = cnt + !!extra_top_pc;
36 CHECK_LE(size, kStackTraceMax);
37 internal_memcpy(trace_buffer, pcs, cnt * sizeof(trace_buffer[0]));
38 if (extra_top_pc)
39 trace_buffer[cnt] = extra_top_pc;
40 top_frame_bp = 0;
41 }
42
43 // In GCC on ARM bp points to saved lr, not fp, so we should check the next
44 // cell in stack to be a saved frame pointer. GetCanonicFrame returns the
45 // pointer to saved frame pointer in any case.
GetCanonicFrame(uptr bp,uptr stack_top,uptr stack_bottom)46 static inline uhwptr *GetCanonicFrame(uptr bp,
47 uptr stack_top,
48 uptr stack_bottom) {
49 #ifdef __arm__
50 if (!IsValidFrame(bp, stack_top, stack_bottom)) return 0;
51 uhwptr *bp_prev = (uhwptr *)bp;
52 if (IsValidFrame((uptr)bp_prev[0], stack_top, stack_bottom)) return bp_prev;
53 // The next frame pointer does not look right. This could be a GCC frame, step
54 // back by 1 word and try again.
55 if (IsValidFrame((uptr)bp_prev[-1], stack_top, stack_bottom))
56 return bp_prev - 1;
57 // Nope, this does not look right either. This means the frame after next does
58 // not have a valid frame pointer, but we can still extract the caller PC.
59 // Unfortunately, there is no way to decide between GCC and LLVM frame
60 // layouts. Assume LLVM.
61 return bp_prev;
62 #else
63 return (uhwptr*)bp;
64 #endif
65 }
66
FastUnwindStack(uptr pc,uptr bp,uptr stack_top,uptr stack_bottom,u32 max_depth)67 void BufferedStackTrace::FastUnwindStack(uptr pc, uptr bp, uptr stack_top,
68 uptr stack_bottom, u32 max_depth) {
69 const uptr kPageSize = GetPageSizeCached();
70 CHECK_GE(max_depth, 2);
71 trace_buffer[0] = pc;
72 size = 1;
73 if (stack_top < 4096) return; // Sanity check for stack top.
74 uhwptr *frame = GetCanonicFrame(bp, stack_top, stack_bottom);
75 // Lowest possible address that makes sense as the next frame pointer.
76 // Goes up as we walk the stack.
77 uptr bottom = stack_bottom;
78 // Avoid infinite loop when frame == frame[0] by using frame > prev_frame.
79 while (IsValidFrame((uptr)frame, stack_top, bottom) &&
80 IsAligned((uptr)frame, sizeof(*frame)) &&
81 size < max_depth) {
82 #ifdef __powerpc__
83 // PowerPC ABIs specify that the return address is saved at offset
84 // 16 of the *caller's* stack frame. Thus we must dereference the
85 // back chain to find the caller frame before extracting it.
86 uhwptr *caller_frame = (uhwptr*)frame[0];
87 if (!IsValidFrame((uptr)caller_frame, stack_top, bottom) ||
88 !IsAligned((uptr)caller_frame, sizeof(uhwptr)))
89 break;
90 uhwptr pc1 = caller_frame[2];
91 #elif defined(__s390__)
92 uhwptr pc1 = frame[14];
93 #else
94 uhwptr pc1 = frame[1];
95 #endif
96 // Let's assume that any pointer in the 0th page (i.e. <0x1000 on i386 and
97 // x86_64) is invalid and stop unwinding here. If we're adding support for
98 // a platform where this isn't true, we need to reconsider this check.
99 if (pc1 < kPageSize)
100 break;
101 if (pc1 != pc) {
102 trace_buffer[size++] = (uptr) pc1;
103 }
104 bottom = (uptr)frame;
105 frame = GetCanonicFrame((uptr)frame[0], stack_top, bottom);
106 }
107 }
108
MatchPc(uptr cur_pc,uptr trace_pc,uptr threshold)109 static bool MatchPc(uptr cur_pc, uptr trace_pc, uptr threshold) {
110 return cur_pc - trace_pc <= threshold || trace_pc - cur_pc <= threshold;
111 }
112
PopStackFrames(uptr count)113 void BufferedStackTrace::PopStackFrames(uptr count) {
114 CHECK_LT(count, size);
115 size -= count;
116 for (uptr i = 0; i < size; ++i) {
117 trace_buffer[i] = trace_buffer[i + count];
118 }
119 }
120
LocatePcInTrace(uptr pc)121 uptr BufferedStackTrace::LocatePcInTrace(uptr pc) {
122 // Use threshold to find PC in stack trace, as PC we want to unwind from may
123 // slightly differ from return address in the actual unwinded stack trace.
124 const int kPcThreshold = 350;
125 for (uptr i = 0; i < size; ++i) {
126 if (MatchPc(pc, trace[i], kPcThreshold))
127 return i;
128 }
129 return 0;
130 }
131
132 } // namespace __sanitizer
133