crashpad/util/misc/capture_context.h
Scott Graham e83103c805 fuchsia: Implement CaptureContext() for x64
Fuchsia enables safe-stack by default in the compiler. Disable it for
the test function so that a candidate RSP value can be found by using
the value of locals on the stack.

(This also reduces the function prolog size sufficiently for the PC
comparison to work, otherwise it required 75 bytes for the delta
comparison.)

Bug: crashpad:196
Change-Id: I2adbcee93c90dbc415309b79e3d16e9c4635f989
Reviewed-on: https://chromium-review.googlesource.com/1000140
Reviewed-by: Joshua Peraza <jperaza@chromium.org>
Commit-Queue: Scott Graham <scottmg@chromium.org>
2018-04-09 20:33:33 +00:00

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// Copyright 2014 The Crashpad Authors. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#ifndef CRASHPAD_UTIL_MISC_CAPTURE_CONTEXT_H_
#define CRASHPAD_UTIL_MISC_CAPTURE_CONTEXT_H_
#include "build/build_config.h"
#if defined(OS_MACOSX)
#include <mach/mach.h>
#elif defined(OS_WIN)
#include <windows.h>
#elif defined(OS_LINUX) || defined(OS_ANDROID)
#include <ucontext.h>
#elif defined(OS_FUCHSIA)
#include <signal.h>
#endif // OS_MACOSX
namespace crashpad {
#if defined(OS_MACOSX)
#if defined(ARCH_CPU_X86_FAMILY)
using NativeCPUContext = x86_thread_state;
#endif
#elif defined(OS_WIN)
using NativeCPUContext = CONTEXT;
#elif defined(OS_LINUX) || defined(OS_ANDROID) || defined(OS_FUCHSIA)
using NativeCPUContext = ucontext_t;
#endif // OS_MACOSX
//! \brief Saves the CPU context.
//!
//! The CPU context will be captured as accurately and completely as possible,
//! containing an atomic snapshot at the point of this functions return. This
//! function does not modify any registers.
//!
//! This function is a replacement for `RtlCaptureContext()` and `getcontext()`
//! which contain bugs and/or limitations.
//!
//! On 32-bit x86, `RtlCaptureContext()` requires that `ebp` be used as a frame
//! pointer, and returns `ebp`, `esp`, and `eip` out of sync with the other
//! registers. Both the 32-bit x86 and 64-bit x86_64 versions of
//! `RtlCaptureContext()` capture only the state of the integer registers,
//! ignoring floating-point and vector state.
//!
//! \param[out] cpu_context The structure to store the context in.
//!
//! \note The ABI may require that this function's argument is passed by
//! register, preventing this fuction from saving the original value of that
//! register. This occurs in the following circumstances:
//!
//! OS | Architecture | Register
//! --------------------|--------------|---------
//! Win | x86_64 | `%%rcx`
//! macOS/Linux/Fuchsia | x86_64 | `%%rdi`
//! Linux | ARM/ARM64 | `r0`/`x0`
//!
//! Additionally, the value `LR` on ARM/ARM64 will be the return address of
//! this function.
//!
//! If the value of these register prior to calling this function are needed
//! they must be obtained separately prior to calling this function. For
//! example:
//! \code
//! uint64_t rdi;
//! asm("movq %%rdi, %0" : "=m"(rdi));
//! \endcode
void CaptureContext(NativeCPUContext* cpu_context);
} // namespace crashpad
#endif // CRASHPAD_UTIL_MISC_CAPTURE_CONTEXT_H_