mfbt/LinuxSignal.h
author Chris Manchester <cmanchester@mozilla.com>
Wed, 16 Jan 2019 22:46:38 +0000
changeset 514323 471d9fab61b34671f974dfa349e7972c200faa2b
parent 508163 6f3709b3878117466168c40affa7bca0b60cf75b
child 514505 5f4630838d46dd81dadb13220a4af0da9e23a619
permissions -rw-r--r--
Bug 1507631 - Remove mentions of MOZ_SIGN_CMD from the build system. r=nalexander Differential Revision: https://phabricator.services.mozilla.com/D16754

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef mozilla_LinuxSignal_h
#define mozilla_LinuxSignal_h

namespace mozilla {

#if defined(__arm__)

// Some (old) Linux kernels on ARM have a bug where a signal handler
// can be called without clearing the IT bits in CPSR first. The result
// is that the first few instructions of the handler could be skipped,
// ultimately resulting in crashes. To workaround this bug, the handler
// on ARM is a trampoline that starts with enough NOP instructions, so
// that even if the IT bits are not cleared, only the NOP instructions
// will be skipped over.

template <void (*H)(int, siginfo_t*, void*)>
__attribute__((naked)) void SignalTrampoline(int aSignal, siginfo_t* aInfo,
                                             void* aContext) {
  asm volatile("nop; nop; nop; nop" : : : "memory");

  asm volatile("b %0" : : "X"(H) : "memory");
}

#define MOZ_SIGNAL_TRAMPOLINE(h) (mozilla::SignalTrampoline<h>)

#else  // __arm__

#define MOZ_SIGNAL_TRAMPOLINE(h) (h)

#endif  // __arm__

}  // namespace mozilla

#endif  // mozilla_LinuxSignal_h