135 lines
4.9 KiB
C++
135 lines
4.9 KiB
C++
// Copyright 2017 The Abseil Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// https://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//
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// This is inspired by Craig Silverstein's PowerPC stacktrace code.
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#ifndef ABSL_DEBUGGING_INTERNAL_STACKTRACE_ARM_INL_H_
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#define ABSL_DEBUGGING_INTERNAL_STACKTRACE_ARM_INL_H_
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#include <cstdint>
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#include "absl/debugging/stacktrace.h"
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// WARNING:
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// This only works if all your code is in either ARM or THUMB mode. With
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// interworking, the frame pointer of the caller can either be in r11 (ARM
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// mode) or r7 (THUMB mode). A callee only saves the frame pointer of its
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// mode in a fixed location on its stack frame. If the caller is a different
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// mode, there is no easy way to find the frame pointer. It can either be
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// still in the designated register or saved on stack along with other callee
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// saved registers.
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// Given a pointer to a stack frame, locate and return the calling
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// stackframe, or return nullptr if no stackframe can be found. Perform sanity
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// checks (the strictness of which is controlled by the boolean parameter
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// "STRICT_UNWINDING") to reduce the chance that a bad pointer is returned.
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template<bool STRICT_UNWINDING>
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static void **NextStackFrame(void **old_sp) {
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void **new_sp = (void**) old_sp[-1];
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// Check that the transition from frame pointer old_sp to frame
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// pointer new_sp isn't clearly bogus
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if (STRICT_UNWINDING) {
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// With the stack growing downwards, older stack frame must be
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// at a greater address that the current one.
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if (new_sp <= old_sp) return nullptr;
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// Assume stack frames larger than 100,000 bytes are bogus.
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if ((uintptr_t)new_sp - (uintptr_t)old_sp > 100000) return nullptr;
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} else {
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// In the non-strict mode, allow discontiguous stack frames.
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// (alternate-signal-stacks for example).
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if (new_sp == old_sp) return nullptr;
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// And allow frames upto about 1MB.
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if ((new_sp > old_sp)
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&& ((uintptr_t)new_sp - (uintptr_t)old_sp > 1000000)) return nullptr;
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}
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if ((uintptr_t)new_sp & (sizeof(void *) - 1)) return nullptr;
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return new_sp;
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}
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// This ensures that absl::GetStackTrace sets up the Link Register properly.
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#ifdef __GNUC__
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void StacktraceArmDummyFunction() __attribute__((noinline));
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void StacktraceArmDummyFunction() { __asm__ volatile(""); }
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#else
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# error StacktraceArmDummyFunction() needs to be ported to this platform.
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#endif
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template <bool IS_STACK_FRAMES, bool IS_WITH_CONTEXT>
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static int UnwindImpl(void** result, int* sizes, int max_depth, int skip_count,
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const void * /* ucp */, int *min_dropped_frames) {
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#ifdef __GNUC__
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void **sp = reinterpret_cast<void**>(__builtin_frame_address(0));
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#else
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# error reading stack point not yet supported on this platform.
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#endif
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// On ARM, the return address is stored in the link register (r14).
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// This is not saved on the stack frame of a leaf function. To
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// simplify code that reads return addresses, we call a dummy
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// function so that the return address of this function is also
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// stored in the stack frame. This works at least for gcc.
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StacktraceArmDummyFunction();
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int n = 0;
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while (sp && n < max_depth) {
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// The absl::GetStackFrames routine is called when we are in some
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// informational context (the failure signal handler for example).
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// Use the non-strict unwinding rules to produce a stack trace
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// that is as complete as possible (even if it contains a few bogus
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// entries in some rare cases).
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void **next_sp = NextStackFrame<!IS_STACK_FRAMES>(sp);
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if (skip_count > 0) {
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skip_count--;
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} else {
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result[n] = *sp;
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if (IS_STACK_FRAMES) {
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if (next_sp > sp) {
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sizes[n] = (uintptr_t)next_sp - (uintptr_t)sp;
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} else {
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// A frame-size of 0 is used to indicate unknown frame size.
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sizes[n] = 0;
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}
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}
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n++;
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}
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sp = next_sp;
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}
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if (min_dropped_frames != nullptr) {
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// Implementation detail: we clamp the max of frames we are willing to
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// count, so as not to spend too much time in the loop below.
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const int kMaxUnwind = 200;
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int j = 0;
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for (; sp != nullptr && j < kMaxUnwind; j++) {
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sp = NextStackFrame<!IS_STACK_FRAMES>(sp);
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}
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*min_dropped_frames = j;
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}
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return n;
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}
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namespace absl {
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ABSL_NAMESPACE_BEGIN
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namespace debugging_internal {
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bool StackTraceWorksForTest() {
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return false;
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}
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} // namespace debugging_internal
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ABSL_NAMESPACE_END
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} // namespace absl
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#endif // ABSL_DEBUGGING_INTERNAL_STACKTRACE_ARM_INL_H_
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