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![Vyacheslav Egorov](/assets/img/avatar_default.png)
Previous workaround was only compilable by GCC - new one is compilable with both but is less robust because theoretically compiler can simply use registers r0-r2 as temporaries whenever it desires. Bug: https://github.com/flutter/flutter/issues/22172 Change-Id: Ic73fde8d3342c1455ab01ed8b7d4b267aebda136 Reviewed-on: https://dart-review.googlesource.com/76021 Reviewed-by: Zach Anderson <zra@google.com> Commit-Queue: Vyacheslav Egorov <vegorov@google.com>
126 lines
4.8 KiB
C++
126 lines
4.8 KiB
C++
// Copyright (c) 2013, the Dart project authors. Please see the AUTHORS file
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// for details. All rights reserved. Use of this source code is governed by a
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// BSD-style license that can be found in the LICENSE file.
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#ifndef RUNTIME_VM_SIGNAL_HANDLER_H_
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#define RUNTIME_VM_SIGNAL_HANDLER_H_
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#include "vm/allocation.h"
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#include "vm/globals.h"
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#if defined(HOST_OS_LINUX)
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#include <signal.h> // NOLINT
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#include <ucontext.h> // NOLINT
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#elif defined(HOST_OS_ANDROID)
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#include <signal.h> // NOLINT
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#if !defined(__BIONIC_HAVE_UCONTEXT_T)
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#include <asm/sigcontext.h> // NOLINT
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// If ucontext_t is not defined on Android, define it here.
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typedef struct sigcontext mcontext_t;
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typedef struct ucontext {
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uint32_t uc_flags;
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struct ucontext* uc_link;
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stack_t uc_stack;
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struct sigcontext uc_mcontext;
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uint32_t uc_sigmask;
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} ucontext_t;
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#endif // !defined(__BIONIC_HAVE_UCONTEXT_T)
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#elif defined(HOST_OS_MACOS)
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#include <signal.h> // NOLINT
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#include <sys/ucontext.h> // NOLINT
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#elif defined(HOST_OS_WINDOWS)
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// Stub out for windows.
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struct siginfo_t;
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struct mcontext_t;
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struct sigset_t {};
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#elif defined(HOST_OS_FUCHSIA)
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#include <signal.h> // NOLINT
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#include <ucontext.h> // NOLINT
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#endif
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// Old linux kernels on ARM might require a trampoline to
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// work around incorrect Thumb -> ARM transitions. See SignalHandlerTrampoline
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// below for more details.
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#if defined(HOST_ARCH_ARM) && \
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(defined(HOST_OS_LINUX) || defined(HOST_OS_ANDROID)) && \
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!defined(__thumb__)
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#define USE_SIGNAL_HANDLER_TRAMPOLINE
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#endif
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namespace dart {
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typedef void (*SignalAction)(int signal, siginfo_t* info, void* context);
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class SignalHandler : public AllStatic {
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public:
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template <SignalAction action>
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static void Install() {
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#if defined(USE_SIGNAL_HANDLER_TRAMPOLINE)
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InstallImpl(SignalHandlerTrampoline<action>);
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#else
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InstallImpl(action);
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#endif // defined(USE_SIGNAL_HANDLER_TRAMPOLINE)
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}
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static void Remove();
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static uintptr_t GetProgramCounter(const mcontext_t& mcontext);
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static uintptr_t GetFramePointer(const mcontext_t& mcontext);
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static uintptr_t GetCStackPointer(const mcontext_t& mcontext);
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static uintptr_t GetDartStackPointer(const mcontext_t& mcontext);
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static uintptr_t GetLinkRegister(const mcontext_t& mcontext);
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private:
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static void InstallImpl(SignalAction action);
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#if defined(USE_SIGNAL_HANDLER_TRAMPOLINE)
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// Work around for a bug in old kernels (only fixed in 3.18 Android kernel):
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//
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// Kernel does not clear If-Then execution state bits when entering ARM signal
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// handler which violates requirements imposed by ARM architecture reference.
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// Some CPUs look at these bits even while in ARM mode which causes them
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// to skip some instructions in the prologue of the signal handler.
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//
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// To work around the issue we insert enough NOPs in the prologue to ensure
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// that no actual instructions are skipped and then branch to the actual
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// signal handler.
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//
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// For the kernel patch that fixes the issue see:
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// http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=6ecf830e5029598732e04067e325d946097519cb
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//
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// Note: this function is marked "naked" because we must guarantee that
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// our NOPs occur before any compiler generated prologue.
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template <SignalAction action>
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static __attribute__((naked)) void SignalHandlerTrampoline(int signal,
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siginfo_t* info,
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void* context_) {
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// IT (If-Then) instruction makes up to four instructions that follow it
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// conditional.
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// Note: clobber all register so that compiler does not attempt to hoist
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// anything from the next assembly block past this one.
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asm volatile("nop; nop; nop; nop;"
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:
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:
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: "r0", "r1", "r2", "r3", "r4", "r5", "r6", "r7", "r8", "r9",
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"r10", "r11", "r12", "r13", "r14", "memory");
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// Tail-call into the actual signal handler.
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//
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// Note: this code is split into a separate inline assembly block because
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// any code that compiler generates to satisfy register constraints must
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// be generated after four NOPs.
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//
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// Note: there is no portable way to specify that we want to have
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// signal, info and context_ in r0 - r2 respectively. So we just mark them
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// as clobbered and hope that compiler does not emit any code that uses
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// these registers to satisfy action constraint (we tested on clang and
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// the generated code looks like one would expect).
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asm volatile("bx %0;" : : "r"(action) : "r0", "r1", "r2", "memory");
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}
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#endif // defined(USE_SIGNAL_HANDLER_TRAMPOLINE)
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};
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#undef USE_SIGNAL_HANDLER_TRAMPOLINE
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} // namespace dart
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#endif // RUNTIME_VM_SIGNAL_HANDLER_H_
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