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/*
* Copyright (C) 2010 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
* THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "config.h"
#include "OSAllocator.h"
#if OS(UNIX)
#include "PageAllocation.h"
#include <errno.h>
#include <sys/mman.h>
#include <wtf/Assertions.h>
namespace WTF {
#if CPU(MIPS)
static bool isWithin256MB(const void* ptr, size_t length)
{
const intptr_t start = reinterpret_cast<intptr_t>(ptr);
const intptr_t end = start + length - 1;
return (start & 0xf0000000) == (end & 0xf0000000);
}
#endif // CPU(MIPS)
void* OSAllocator::reserveUncommitted(size_t bytes, Usage usage, bool writable, bool executable, bool includesGuardPages)
{
#if OS(QNX)
UNUSED_PARAM(usage);
UNUSED_PARAM(writable);
UNUSED_PARAM(executable);
UNUSED_PARAM(includesGuardPages);
// Reserve memory with PROT_NONE and MAP_LAZY so it isn't committed now.
void* result = mmap(0, bytes, PROT_NONE, MAP_LAZY | MAP_PRIVATE | MAP_ANON, -1, 0);
if (result == MAP_FAILED)
CRASH();
#elif OS(LINUX)
UNUSED_PARAM(usage);
UNUSED_PARAM(writable);
#if !CPU(MIPS)
UNUSED_PARAM(executable);
#endif
UNUSED_PARAM(includesGuardPages);
void* result = mmap(0, bytes, PROT_NONE, MAP_NORESERVE | MAP_PRIVATE | MAP_ANON, -1, 0);
if (result == MAP_FAILED)
CRASH();
#if CPU(MIPS)
// On MIPS we can use shorter j <address> jump instructions if the executable
// memory resides entirely within a single 256MB page (e.g. 0x3000.0000 to 0x3fff.ffff).
// Usually this is true for the small buffers we allocate, but we test, and upon failure
// we reallocate a double-size region, choose a valid region, and unmap the remainder.
if (executable && UNLIKELY(!isWithin256MB(result, bytes))) {
// Not in 256MB region, try to map double size.
if (munmap(result, bytes))
CRASH();
result = mmap(0, 2 * bytes, PROT_NONE, MAP_NORESERVE | MAP_PRIVATE | MAP_ANON, -1, 0);
if (result == MAP_FAILED)
CRASH();
if (isWithin256MB(result, bytes)) {
// 1st half is good, release 2nd half.
if (munmap(reinterpret_cast<int8_t*>(result) + bytes, bytes))
CRASH();
} else if (isWithin256MB(reinterpret_cast<int8_t*>(result) + bytes, bytes)) {
// 2nd half is good, release 1st half.
if (munmap(result, bytes))
CRASH();
result = reinterpret_cast<int8_t*>(result) + bytes;
} else
ASSERT_NOT_REACHED();
}
#endif // CPU(MIPS)
madvise(result, bytes, MADV_DONTNEED);
#else
void* result = reserveAndCommit(bytes, usage, writable, executable, includesGuardPages);
#if HAVE(MADV_FREE_REUSE)
// To support the "reserve then commit" model, we have to initially decommit.
while (madvise(result, bytes, MADV_FREE_REUSABLE) == -1 && errno == EAGAIN) { }
#endif
#endif // OS(QNX)
return result;
}
void* OSAllocator::reserveAndCommit(size_t bytes, Usage usage, bool writable, bool executable, bool includesGuardPages)
{
// All POSIX reservations start out logically committed.
int protection = PROT_READ;
if (writable)
protection |= PROT_WRITE;
if (executable)
protection |= PROT_EXEC;
int flags = MAP_PRIVATE | MAP_ANON;
#if PLATFORM(IOS)
if (executable)
flags |= MAP_JIT;
#endif
#if OS(DARWIN)
int fd = usage;
#else
UNUSED_PARAM(usage);
int fd = -1;
#endif
void* result = 0;
#if (OS(DARWIN) && CPU(X86_64))
if (executable) {
ASSERT(includesGuardPages);
// Cook up an address to allocate at, using the following recipe:
// 17 bits of zero, stay in userspace kids.
// 26 bits of randomness for ASLR.
// 21 bits of zero, at least stay aligned within one level of the pagetables.
//
// But! - as a temporary workaround for some plugin problems (rdar://problem/6812854),
// for now instead of 2^26 bits of ASLR lets stick with 25 bits of randomization plus
// 2^24, which should put up somewhere in the middle of userspace (in the address range
// 0x200000000000 .. 0x5fffffffffff).
intptr_t randomLocation = 0;
randomLocation = arc4random() & ((1 << 25) - 1);
randomLocation += (1 << 24);
randomLocation <<= 21;
result = reinterpret_cast<void*>(randomLocation);
}
#endif
result = mmap(result, bytes, protection, flags, fd, 0);
if (result == MAP_FAILED) {
#if ENABLE(LLINT)
if (executable)
result = 0;
else
#endif
CRASH();
}
if (result && includesGuardPages) {
// We use mmap to remap the guardpages rather than using mprotect as
// mprotect results in multiple references to the code region. This
// breaks the madvise based mechanism we use to return physical memory
// to the OS.
mmap(result, pageSize(), PROT_NONE, MAP_FIXED | MAP_PRIVATE | MAP_ANON, fd, 0);
mmap(static_cast<char*>(result) + bytes - pageSize(), pageSize(), PROT_NONE, MAP_FIXED | MAP_PRIVATE | MAP_ANON, fd, 0);
}
return result;
}
void OSAllocator::commit(void* address, size_t bytes, bool writable, bool executable)
{
#if OS(QNX)
int protection = PROT_READ;
if (writable)
protection |= PROT_WRITE;
if (executable)
protection |= PROT_EXEC;
if (MAP_FAILED == mmap(address, bytes, protection, MAP_FIXED | MAP_PRIVATE | MAP_ANON, -1, 0))
CRASH();
#elif OS(LINUX)
int protection = PROT_READ;
if (writable)
protection |= PROT_WRITE;
if (executable)
protection |= PROT_EXEC;
if (mprotect(address, bytes, protection))
CRASH();
madvise(address, bytes, MADV_WILLNEED);
#elif HAVE(MADV_FREE_REUSE)
UNUSED_PARAM(writable);
UNUSED_PARAM(executable);
while (madvise(address, bytes, MADV_FREE_REUSE) == -1 && errno == EAGAIN) { }
#else
// Non-MADV_FREE_REUSE reservations automatically commit on demand.
UNUSED_PARAM(address);
UNUSED_PARAM(bytes);
UNUSED_PARAM(writable);
UNUSED_PARAM(executable);
#endif
}
void OSAllocator::decommit(void* address, size_t bytes)
{
#if OS(QNX)
// Use PROT_NONE and MAP_LAZY to decommit the pages.
mmap(address, bytes, PROT_NONE, MAP_FIXED | MAP_LAZY | MAP_PRIVATE | MAP_ANON, -1, 0);
#elif OS(LINUX)
madvise(address, bytes, MADV_DONTNEED);
if (mprotect(address, bytes, PROT_NONE))
CRASH();
#elif HAVE(MADV_FREE_REUSE)
while (madvise(address, bytes, MADV_FREE_REUSABLE) == -1 && errno == EAGAIN) { }
#elif HAVE(MADV_FREE)
while (madvise(address, bytes, MADV_FREE) == -1 && errno == EAGAIN) { }
#elif HAVE(MADV_DONTNEED)
while (madvise(address, bytes, MADV_DONTNEED) == -1 && errno == EAGAIN) { }
#else
UNUSED_PARAM(address);
UNUSED_PARAM(bytes);
#endif
}
void OSAllocator::releaseDecommitted(void* address, size_t bytes)
{
int result = munmap(address, bytes);
if (result == -1)
CRASH();
}
} // namespace WTF
#endif // OS(UNIX)
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