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 #include "sanitizer_ptrauth.h" 19 20 namespace __sanitizer { 21 22 uptr StackTrace::GetNextInstructionPc(uptr pc) { 23 #if defined(__aarch64__) 24 return STRIP_PAC_PC((void *)pc) + 4; 25 #elif defined(__sparc__) || defined(__mips__) 26 return pc + 8; 27 #elif SANITIZER_RISCV64 28 // Current check order is 4 -> 2 -> 6 -> 8 29 u8 InsnByte = *(u8 *)(pc); 30 if (((InsnByte & 0x3) == 0x3) && ((InsnByte & 0x1c) != 0x1c)) { 31 // xxxxxxxxxxxbbb11 | 32 bit | bbb != 111 32 return pc + 4; 33 } 34 if ((InsnByte & 0x3) != 0x3) { 35 // xxxxxxxxxxxxxxaa | 16 bit | aa != 11 36 return pc + 2; 37 } 38 // RISC-V encoding allows instructions to be up to 8 bytes long 39 if ((InsnByte & 0x3f) == 0x1f) { 40 // xxxxxxxxxx011111 | 48 bit | 41 return pc + 6; 42 } 43 if ((InsnByte & 0x7f) == 0x3f) { 44 // xxxxxxxxx0111111 | 64 bit | 45 return pc + 8; 46 } 47 // bail-out if could not figure out the instruction size 48 return 0; 49 #elif SANITIZER_S390 || SANITIZER_I386 || SANITIZER_X32 || SANITIZER_X64 50 return pc + 1; 51 #else 52 return pc + 4; 53 #endif 54 } 55 56 uptr StackTrace::GetCurrentPc() { 57 return GET_CALLER_PC(); 58 } 59 60 void BufferedStackTrace::Init(const uptr *pcs, uptr cnt, uptr extra_top_pc) { 61 size = cnt + !!extra_top_pc; 62 CHECK_LE(size, kStackTraceMax); 63 internal_memcpy(trace_buffer, pcs, cnt * sizeof(trace_buffer[0])); 64 if (extra_top_pc) 65 trace_buffer[cnt] = extra_top_pc; 66 top_frame_bp = 0; 67 } 68 69 // Sparc implementation is in its own file. 70 #if !defined(__sparc__) 71 72 // In GCC on ARM bp points to saved lr, not fp, so we should check the next 73 // cell in stack to be a saved frame pointer. GetCanonicFrame returns the 74 // pointer to saved frame pointer in any case. 75 static inline uhwptr *GetCanonicFrame(uptr bp, 76 uptr stack_top, 77 uptr stack_bottom) { 78 CHECK_GT(stack_top, stack_bottom); 79 #ifdef __arm__ 80 if (!IsValidFrame(bp, stack_top, stack_bottom)) return 0; 81 uhwptr *bp_prev = (uhwptr *)bp; 82 if (IsValidFrame((uptr)bp_prev[0], stack_top, stack_bottom)) return bp_prev; 83 // The next frame pointer does not look right. This could be a GCC frame, step 84 // back by 1 word and try again. 85 if (IsValidFrame((uptr)bp_prev[-1], stack_top, stack_bottom)) 86 return bp_prev - 1; 87 // Nope, this does not look right either. This means the frame after next does 88 // not have a valid frame pointer, but we can still extract the caller PC. 89 // Unfortunately, there is no way to decide between GCC and LLVM frame 90 // layouts. Assume LLVM. 91 return bp_prev; 92 #else 93 return (uhwptr*)bp; 94 #endif 95 } 96 97 void BufferedStackTrace::UnwindFast(uptr pc, uptr bp, uptr stack_top, 98 uptr stack_bottom, u32 max_depth) { 99 // TODO(yln): add arg sanity check for stack_top/stack_bottom 100 CHECK_GE(max_depth, 2); 101 const uptr kPageSize = GetPageSizeCached(); 102 trace_buffer[0] = pc; 103 size = 1; 104 if (stack_top < 4096) return; // Sanity check for stack top. 105 uhwptr *frame = GetCanonicFrame(bp, stack_top, stack_bottom); 106 // Lowest possible address that makes sense as the next frame pointer. 107 // Goes up as we walk the stack. 108 uptr bottom = stack_bottom; 109 // Avoid infinite loop when frame == frame[0] by using frame > prev_frame. 110 while (IsValidFrame((uptr)frame, stack_top, bottom) && 111 IsAligned((uptr)frame, sizeof(*frame)) && 112 size < max_depth) { 113 #ifdef __powerpc__ 114 // PowerPC ABIs specify that the return address is saved at offset 115 // 16 of the *caller's* stack frame. Thus we must dereference the 116 // back chain to find the caller frame before extracting it. 117 uhwptr *caller_frame = (uhwptr*)frame[0]; 118 if (!IsValidFrame((uptr)caller_frame, stack_top, bottom) || 119 !IsAligned((uptr)caller_frame, sizeof(uhwptr))) 120 break; 121 uhwptr pc1 = caller_frame[2]; 122 #elif defined(__s390__) 123 uhwptr pc1 = frame[14]; 124 #elif defined(__loongarch__) || defined(__riscv) 125 // frame[-1] contains the return address 126 uhwptr pc1 = frame[-1]; 127 #else 128 uhwptr pc1 = STRIP_PAC_PC((void *)frame[1]); 129 #endif 130 // Let's assume that any pointer in the 0th page (i.e. <0x1000 on i386 and 131 // x86_64) is invalid and stop unwinding here. If we're adding support for 132 // a platform where this isn't true, we need to reconsider this check. 133 if (pc1 < kPageSize) 134 break; 135 if (pc1 != pc) { 136 trace_buffer[size++] = (uptr) pc1; 137 } 138 bottom = (uptr)frame; 139 #if defined(__loongarch__) || defined(__riscv) 140 // frame[-2] contain fp of the previous frame 141 uptr new_bp = (uptr)frame[-2]; 142 #else 143 uptr new_bp = (uptr)frame[0]; 144 #endif 145 frame = GetCanonicFrame(new_bp, stack_top, bottom); 146 } 147 } 148 149 #endif // !defined(__sparc__) 150 151 void BufferedStackTrace::PopStackFrames(uptr count) { 152 CHECK_LT(count, size); 153 size -= count; 154 for (uptr i = 0; i < size; ++i) { 155 trace_buffer[i] = trace_buffer[i + count]; 156 } 157 } 158 159 static uptr Distance(uptr a, uptr b) { return a < b ? b - a : a - b; } 160 161 uptr BufferedStackTrace::LocatePcInTrace(uptr pc) { 162 uptr best = 0; 163 for (uptr i = 1; i < size; ++i) { 164 if (Distance(trace[i], pc) < Distance(trace[best], pc)) best = i; 165 } 166 return best; 167 } 168 169 } // namespace __sanitizer 170