mirror of
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106 lines
3.1 KiB
C++
106 lines
3.1 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifdef ANDROID
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#include "mozilla/TaggedAnonymousMemory.h"
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#include <sys/types.h>
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#include <sys/mman.h>
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#include <sys/prctl.h>
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#include <sys/syscall.h>
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#include <unistd.h>
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#include "mozilla/Assertions.h"
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// These constants are copied from <sys/prctl.h>, because the headers
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// used for building may not have them even though the running kernel
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// supports them.
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#ifndef PR_SET_VMA
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#define PR_SET_VMA 0x53564d41
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#endif
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#ifndef PR_SET_VMA_ANON_NAME
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#define PR_SET_VMA_ANON_NAME 0
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#endif
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namespace mozilla {
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// Returns 0 for success and -1 (with errno) for error.
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static int
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TagAnonymousMemoryAligned(const void* aPtr, size_t aLength, const char* aTag)
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{
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return prctl(PR_SET_VMA,
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PR_SET_VMA_ANON_NAME,
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reinterpret_cast<unsigned long>(aPtr),
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aLength,
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reinterpret_cast<unsigned long>(aTag));
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}
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// On some architectures, it's possible for the page size to be larger
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// than the PAGE_SIZE we were compiled with. This computes the
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// equivalent of PAGE_MASK.
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static uintptr_t
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GetPageMask()
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{
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static uintptr_t mask = 0;
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if (mask == 0) {
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uintptr_t pageSize = sysconf(_SC_PAGESIZE);
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mask = ~(pageSize - 1);
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MOZ_ASSERT((pageSize & (pageSize - 1)) == 0,
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"Page size must be a power of 2!");
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}
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return mask;
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}
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} // namespace mozilla
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int
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MozTaggedMemoryIsSupported(void)
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{
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static int supported = -1;
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if (supported == -1) {
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// Tagging an empty range always "succeeds" if the feature is supported,
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// regardless of the start pointer.
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supported = mozilla::TagAnonymousMemoryAligned(nullptr, 0, nullptr) == 0;
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}
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return supported;
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}
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void
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MozTagAnonymousMemory(const void* aPtr, size_t aLength, const char* aTag)
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{
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if (MozTaggedMemoryIsSupported()) {
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// The kernel will round up the end of the range to the next page
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// boundary if it's not aligned (comments indicate this behavior
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// is based on that of madvise), but it will reject the request if
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// the start is not aligned. We therefore round down the start
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// address and adjust the length accordingly.
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uintptr_t addr = reinterpret_cast<uintptr_t>(aPtr);
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uintptr_t end = addr + aLength;
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uintptr_t addrRounded = addr & mozilla::GetPageMask();
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const void* ptrRounded = reinterpret_cast<const void*>(addrRounded);
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mozilla::TagAnonymousMemoryAligned(ptrRounded, end - addrRounded, aTag);
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}
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}
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void*
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MozTaggedAnonymousMmap(void* aAddr, size_t aLength, int aProt, int aFlags,
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int aFd, off_t aOffset, const char* aTag)
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{
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void* mapped = mmap(aAddr, aLength, aProt, aFlags, aFd, aOffset);
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if (MozTaggedMemoryIsSupported() &&
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(aFlags & MAP_ANONYMOUS) == MAP_ANONYMOUS &&
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mapped != MAP_FAILED) {
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mozilla::TagAnonymousMemoryAligned(mapped, aLength, aTag);
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}
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return mapped;
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}
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#endif // ANDROID
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