259 lines
10 KiB
C++
259 lines
10 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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// Produce stack trace. I'm guessing (hoping!) the code is much like
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// for x86. For apple machines, at least, it seems to be; see
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// https://developer.apple.com/documentation/mac/runtimehtml/RTArch-59.html
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// https://www.linux-foundation.org/spec/ELF/ppc64/PPC-elf64abi-1.9.html#STACK
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// Linux has similar code: http://patchwork.ozlabs.org/linuxppc/patch?id=8882
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#ifndef ABSL_DEBUGGING_INTERNAL_STACKTRACE_POWERPC_INL_H_
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#define ABSL_DEBUGGING_INTERNAL_STACKTRACE_POWERPC_INL_H_
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#if defined(__linux__)
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#include <asm/ptrace.h> // for PT_NIP.
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#include <ucontext.h> // for ucontext_t
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#endif
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#include <unistd.h>
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#include <cassert>
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#include <cstdint>
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#include <cstdio>
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#include "absl/base/attributes.h"
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#include "absl/base/optimization.h"
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#include "absl/base/port.h"
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#include "absl/debugging/stacktrace.h"
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#include "absl/debugging/internal/address_is_readable.h"
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#include "absl/debugging/internal/vdso_support.h" // a no-op on non-elf or non-glibc systems
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// Given a stack pointer, return the saved link register value.
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// Note that this is the link register for a callee.
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static inline void *StacktracePowerPCGetLR(void **sp) {
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// PowerPC has 3 main ABIs, which say where in the stack the
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// Link Register is. For DARWIN and AIX (used by apple and
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// linux ppc64), it's in sp[2]. For SYSV (used by linux ppc),
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// it's in sp[1].
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#if defined(_CALL_AIX) || defined(_CALL_DARWIN)
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return *(sp+2);
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#elif defined(_CALL_SYSV)
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return *(sp+1);
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#elif defined(__APPLE__) || defined(__FreeBSD__) || \
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(defined(__linux__) && defined(__PPC64__))
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// This check is in case the compiler doesn't define _CALL_AIX/etc.
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return *(sp+2);
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#elif defined(__linux)
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// This check is in case the compiler doesn't define _CALL_SYSV.
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return *(sp+1);
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#else
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#error Need to specify the PPC ABI for your archiecture.
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#endif
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}
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// Given a pointer to a stack frame, locate and return the calling
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// stackframe, or return null 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, bool IS_WITH_CONTEXT>
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ABSL_ATTRIBUTE_NO_SANITIZE_ADDRESS // May read random elements from stack.
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ABSL_ATTRIBUTE_NO_SANITIZE_MEMORY // May read random elements from stack.
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static void **NextStackFrame(void **old_sp, const void *uc) {
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void **new_sp = (void **) *old_sp;
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enum { kStackAlignment = 16 };
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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 % kStackAlignment != 0) return nullptr;
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#if defined(__linux__)
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enum StackTraceKernelSymbolStatus {
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kNotInitialized = 0, kAddressValid, kAddressInvalid };
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if (IS_WITH_CONTEXT && uc != nullptr) {
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static StackTraceKernelSymbolStatus kernel_symbol_status =
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kNotInitialized; // Sentinel: not computed yet.
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// Initialize with sentinel value: __kernel_rt_sigtramp_rt64 can not
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// possibly be there.
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static const unsigned char *kernel_sigtramp_rt64_address = nullptr;
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if (kernel_symbol_status == kNotInitialized) {
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absl::debugging_internal::VDSOSupport vdso;
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if (vdso.IsPresent()) {
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absl::debugging_internal::VDSOSupport::SymbolInfo
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sigtramp_rt64_symbol_info;
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if (!vdso.LookupSymbol(
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"__kernel_sigtramp_rt64", "LINUX_2.6.15",
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absl::debugging_internal::VDSOSupport::kVDSOSymbolType,
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&sigtramp_rt64_symbol_info) ||
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sigtramp_rt64_symbol_info.address == nullptr) {
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// Unexpected: VDSO is present, yet the expected symbol is missing
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// or null.
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assert(false && "VDSO is present, but doesn't have expected symbol");
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kernel_symbol_status = kAddressInvalid;
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} else {
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kernel_sigtramp_rt64_address =
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reinterpret_cast<const unsigned char *>(
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sigtramp_rt64_symbol_info.address);
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kernel_symbol_status = kAddressValid;
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}
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} else {
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kernel_symbol_status = kAddressInvalid;
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}
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}
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if (new_sp != nullptr &&
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kernel_symbol_status == kAddressValid &&
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StacktracePowerPCGetLR(new_sp) == kernel_sigtramp_rt64_address) {
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const ucontext_t* signal_context =
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reinterpret_cast<const ucontext_t*>(uc);
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void **const sp_before_signal =
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#if defined(__PPC64__)
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reinterpret_cast<void **>(signal_context->uc_mcontext.gp_regs[PT_R1]);
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#else
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reinterpret_cast<void **>(
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signal_context->uc_mcontext.uc_regs->gregs[PT_R1]);
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#endif
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// Check that alleged sp before signal is nonnull and is reasonably
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// aligned.
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if (sp_before_signal != nullptr &&
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((uintptr_t)sp_before_signal % kStackAlignment) == 0) {
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// Check that alleged stack pointer is actually readable. This is to
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// prevent a "double fault" in case we hit the first fault due to e.g.
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// a stack corruption.
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if (absl::debugging_internal::AddressIsReadable(sp_before_signal)) {
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// Alleged stack pointer is readable, use it for further unwinding.
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new_sp = sp_before_signal;
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}
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}
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}
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}
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#endif
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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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ABSL_ATTRIBUTE_NOINLINE static void AbslStacktracePowerPCDummyFunction() {
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ABSL_BLOCK_TAIL_CALL_OPTIMIZATION();
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}
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template <bool IS_STACK_FRAMES, bool IS_WITH_CONTEXT>
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ABSL_ATTRIBUTE_NO_SANITIZE_ADDRESS // May read random elements from stack.
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ABSL_ATTRIBUTE_NO_SANITIZE_MEMORY // May read random elements from stack.
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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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void **sp;
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// Apple macOS uses an old version of gnu as -- both Darwin 7.9.0 (Panther)
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// and Darwin 8.8.1 (Tiger) use as 1.38. This means we have to use a
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// different asm syntax. I don't know quite the best way to discriminate
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// systems using the old as from the new one; I've gone with __APPLE__.
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#ifdef __APPLE__
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__asm__ volatile ("mr %0,r1" : "=r" (sp));
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#else
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__asm__ volatile ("mr %0,1" : "=r" (sp));
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#endif
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// On PowerPC, the "Link Register" or "Link Record" (LR), is a stack
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// entry that holds the return address of the subroutine call (what
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// instruction we run after our function finishes). This is the
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// same as the stack-pointer of our parent routine, which is what we
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// want here. While the compiler will always(?) set up LR for
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// subroutine calls, it may not for leaf functions (such as this one).
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// This routine forces the compiler (at least gcc) to push it anyway.
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AbslStacktracePowerPCDummyFunction();
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// The LR save area is used by the callee, so the top entry is bogus.
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skip_count++;
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int n = 0;
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// Unlike ABIs of X86 and ARM, PowerPC ABIs say that return address (in
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// the link register) of a function call is stored in the caller's stack
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// frame instead of the callee's. When we look for the return address
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// associated with a stack frame, we need to make sure that there is a
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// caller frame before it. So we call NextStackFrame before entering the
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// loop below and check next_sp instead of sp for loop termination.
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// The outermost frame is set up by runtimes and it does not have a
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// caller frame, so it is skipped.
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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
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// bogus entries in some rare cases).
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void **next_sp = NextStackFrame<!IS_STACK_FRAMES, IS_WITH_CONTEXT>(sp, ucp);
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while (next_sp && n < max_depth) {
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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] = StacktracePowerPCGetLR(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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next_sp = NextStackFrame<!IS_STACK_FRAMES, IS_WITH_CONTEXT>(sp, ucp);
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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 = 1000;
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int num_dropped_frames = 0;
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for (int j = 0; next_sp != nullptr && j < kMaxUnwind; j++) {
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if (skip_count > 0) {
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skip_count--;
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} else {
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num_dropped_frames++;
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}
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next_sp = NextStackFrame<!IS_STACK_FRAMES, IS_WITH_CONTEXT>(next_sp, ucp);
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}
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*min_dropped_frames = num_dropped_frames;
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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 true;
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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_POWERPC_INL_H_
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