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 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 53 uptr StackTrace::GetCurrentPc() { 54 return GET_CALLER_PC(); 55 } 56 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. 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 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__) 147 148 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 } 155 156 static uptr Distance(uptr a, uptr b) { return a < b ? b - a : a - b; } 157 158 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