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//===-- sanitizer_stacktrace.cpp ------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file is shared between AddressSanitizer and ThreadSanitizer
// run-time libraries.
//===----------------------------------------------------------------------===//
#include "sanitizer_stacktrace.h"
#include "sanitizer_common.h"
#include "sanitizer_flags.h"
#include "sanitizer_platform.h"
#include "sanitizer_ptrauth.h"
namespace __sanitizer {
uptr StackTrace::GetNextInstructionPc(uptr pc) {
#if defined(__sparc__) || defined(__mips__)
return pc + 8;
#elif defined(__powerpc__) || defined(__arm__) || defined(__aarch64__) || \
defined(__hexagon__)
return STRIP_PAC_PC((void *)pc) + 4;
#elif SANITIZER_RISCV64
// Current check order is 4 -> 2 -> 6 -> 8
u8 InsnByte = *(u8 *)(pc);
if (((InsnByte & 0x3) == 0x3) && ((InsnByte & 0x1c) != 0x1c)) {
// xxxxxxxxxxxbbb11 | 32 bit | bbb != 111
return pc + 4;
}
if ((InsnByte & 0x3) != 0x3) {
// xxxxxxxxxxxxxxaa | 16 bit | aa != 11
return pc + 2;
}
// RISC-V encoding allows instructions to be up to 8 bytes long
if ((InsnByte & 0x3f) == 0x1f) {
// xxxxxxxxxx011111 | 48 bit |
return pc + 6;
}
if ((InsnByte & 0x7f) == 0x3f) {
// xxxxxxxxx0111111 | 64 bit |
return pc + 8;
}
// bail-out if could not figure out the instruction size
return 0;
#else
return pc + 1;
#endif
}
uptr StackTrace::GetCurrentPc() {
return GET_CALLER_PC();
}
void BufferedStackTrace::Init(const uptr *pcs, uptr cnt, uptr extra_top_pc) {
size = cnt + !!extra_top_pc;
CHECK_LE(size, kStackTraceMax);
internal_memcpy(trace_buffer, pcs, cnt * sizeof(trace_buffer[0]));
if (extra_top_pc)
trace_buffer[cnt] = extra_top_pc;
top_frame_bp = 0;
}
// Sparc implementation is in its own file.
#if !defined(__sparc__)
// In GCC on ARM bp points to saved lr, not fp, so we should check the next
// cell in stack to be a saved frame pointer. GetCanonicFrame returns the
// pointer to saved frame pointer in any case.
static inline uhwptr *GetCanonicFrame(uptr bp,
uptr stack_top,
uptr stack_bottom) {
CHECK_GT(stack_top, stack_bottom);
#ifdef __arm__
if (!IsValidFrame(bp, stack_top, stack_bottom)) return 0;
uhwptr *bp_prev = (uhwptr *)bp;
if (IsValidFrame((uptr)bp_prev[0], stack_top, stack_bottom)) return bp_prev;
// The next frame pointer does not look right. This could be a GCC frame, step
// back by 1 word and try again.
if (IsValidFrame((uptr)bp_prev[-1], stack_top, stack_bottom))
return bp_prev - 1;
// Nope, this does not look right either. This means the frame after next does
// not have a valid frame pointer, but we can still extract the caller PC.
// Unfortunately, there is no way to decide between GCC and LLVM frame
// layouts. Assume GCC.
return bp_prev - 1;
#else
return (uhwptr*)bp;
#endif
}
void BufferedStackTrace::UnwindFast(uptr pc, uptr bp, uptr stack_top,
uptr stack_bottom, u32 max_depth) {
// TODO(yln): add arg sanity check for stack_top/stack_bottom
CHECK_GE(max_depth, 2);
const uptr kPageSize = GetPageSizeCached();
trace_buffer[0] = pc;
size = 1;
if (stack_top < 4096) return; // Sanity check for stack top.
uhwptr *frame = GetCanonicFrame(bp, stack_top, stack_bottom);
// Lowest possible address that makes sense as the next frame pointer.
// Goes up as we walk the stack.
uptr bottom = stack_bottom;
// Avoid infinite loop when frame == frame[0] by using frame > prev_frame.
while (IsValidFrame((uptr)frame, stack_top, bottom) &&
IsAligned((uptr)frame, sizeof(*frame)) &&
size < max_depth) {
#ifdef __powerpc__
// PowerPC ABIs specify that the return address is saved on the
// *caller's* stack frame. Thus we must dereference the back chain
// to find the caller frame before extracting it.
uhwptr *caller_frame = (uhwptr*)frame[0];
if (!IsValidFrame((uptr)caller_frame, stack_top, bottom) ||
!IsAligned((uptr)caller_frame, sizeof(uhwptr)))
break;
// For most ABIs the offset where the return address is saved is two
// register sizes. The exception is the SVR4 ABI, which uses an
// offset of only one register size.
#ifdef _CALL_SYSV
uhwptr pc1 = caller_frame[1];
#else
uhwptr pc1 = caller_frame[2];
#endif
#elif defined(__s390__)
uhwptr pc1 = frame[14];
#elif defined(__riscv)
// frame[-1] contains the return address
uhwptr pc1 = frame[-1];
#else
uhwptr pc1 = STRIP_PAC_PC((void *)frame[1]);
#endif
// Let's assume that any pointer in the 0th page (i.e. <0x1000 on i386 and
// x86_64) is invalid and stop unwinding here. If we're adding support for
// a platform where this isn't true, we need to reconsider this check.
if (pc1 < kPageSize)
break;
if (pc1 != pc) {
trace_buffer[size++] = (uptr) pc1;
}
bottom = (uptr)frame;
#if defined(__riscv)
// frame[-2] contain fp of the previous frame
uptr new_bp = (uptr)frame[-2];
#else
uptr new_bp = (uptr)frame[0];
#endif
frame = GetCanonicFrame(new_bp, stack_top, bottom);
}
}
#endif // !defined(__sparc__)
void BufferedStackTrace::PopStackFrames(uptr count) {
CHECK_LT(count, size);
size -= count;
for (uptr i = 0; i < size; ++i) {
trace_buffer[i] = trace_buffer[i + count];
}
}
static uptr Distance(uptr a, uptr b) { return a < b ? b - a : a - b; }
uptr BufferedStackTrace::LocatePcInTrace(uptr pc) {
uptr best = 0;
for (uptr i = 1; i < size; ++i) {
if (Distance(trace[i], pc) < Distance(trace[best], pc)) best = i;
}
return best;
}
} // namespace __sanitizer
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