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