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 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 30 uptr StackTrace::GetCurrentPc() { 31 return GET_CALLER_PC(); 32 } 33 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. 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 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 } 108 109 static bool MatchPc(uptr cur_pc, uptr trace_pc, uptr threshold) { 110 return cur_pc - trace_pc <= threshold || trace_pc - cur_pc <= threshold; 111 } 112 113 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 } 120 121 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