| /* |
| * 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" |
| |
| #include "PageAllocation.h" |
| #include <errno.h> |
| #include <sys/mman.h> |
| #include <wtf/Assertions.h> |
| #include <wtf/UnusedParam.h> |
| |
| namespace WTF { |
| |
| void* OSAllocator::reserveUncommitted(size_t bytes, Usage usage, bool writable, bool executable, bool includesGuardPages) |
| { |
| #if OS(QNX) |
| // 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(); |
| #else // OS(QNX) |
| |
| void* result = reserveAndCommit(bytes, usage, writable, executable, includesGuardPages); |
| #if OS(LINUX) |
| madvise(result, bytes, MADV_DONTNEED); |
| #elif 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(LINUX) && CPU(X86_64)) |
| // Linux distros usually do not allow overcommit by default, so |
| // JSC's strategy of mmaping a large amount of memory upfront |
| // won't work very well on some systems. Fortunately there's a |
| // flag we can pass to mmap to disable the overcommit check for |
| // this particular call, so we can get away with it as long as the |
| // overcommit flag value in /proc/sys/vm/overcommit_memory is 0 |
| // ('heuristic') and not 2 (always check). 0 is the usual default |
| // value, so this should work well in general. |
| flags |= MAP_NORESERVE; |
| #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) |
| UNUSED_PARAM(writable); |
| UNUSED_PARAM(executable); |
| 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); |
| #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 |