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![asiva](/assets/img/avatar_default.png)
read the app-jit snapshot into this memory instead of directly mapping the app-jit snapshot. use MAP_JIT option only for executable pages and do not use it on iOS. Change-Id: I8db6f29293677bbf36209473709077115b7b489e Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/113219 Reviewed-by: Ryan Macnak <rmacnak@google.com> Commit-Queue: Siva Annamalai <asiva@google.com>
302 lines
9.8 KiB
C++
302 lines
9.8 KiB
C++
// Copyright (c) 2012, the Dart project authors. Please see the AUTHORS file
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// for details. All rights reserved. Use of this source code is governed by a
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// BSD-style license that can be found in the LICENSE file.
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#include "vm/globals.h"
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#if defined(HOST_OS_ANDROID) || defined(HOST_OS_LINUX) || defined(HOST_OS_MACOS)
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#include "vm/virtual_memory.h"
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#include <errno.h>
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#include <fcntl.h>
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#include <sys/mman.h>
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#include <sys/stat.h>
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#include <sys/syscall.h>
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#include <unistd.h>
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#include "platform/assert.h"
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#include "platform/utils.h"
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#include "vm/isolate.h"
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// #define VIRTUAL_MEMORY_LOGGING 1
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#if defined(VIRTUAL_MEMORY_LOGGING)
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#define LOG_INFO(msg, ...) OS::PrintErr(msg, ##__VA_ARGS__)
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#else
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#define LOG_INFO(msg, ...)
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#endif // defined(VIRTUAL_MEMORY_LOGGING)
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namespace dart {
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// standard MAP_FAILED causes "error: use of old-style cast" as it
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// defines MAP_FAILED as ((void *) -1)
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#undef MAP_FAILED
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#define MAP_FAILED reinterpret_cast<void*>(-1)
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DECLARE_FLAG(bool, dual_map_code);
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DECLARE_FLAG(bool, write_protect_code);
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#if defined(TARGET_OS_LINUX)
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DECLARE_FLAG(bool, generate_perf_events_symbols);
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DECLARE_FLAG(bool, generate_perf_jitdump);
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#endif
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uword VirtualMemory::page_size_ = 0;
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void VirtualMemory::Init() {
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page_size_ = getpagesize();
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#if defined(DUAL_MAPPING_SUPPORTED)
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// Perf is Linux-specific and the flags aren't defined in Product.
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#if defined(TARGET_OS_LINUX) && !defined(PRODUCT)
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// Perf interacts strangely with memfds, leading it to sometimes collect
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// garbled return addresses.
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if (FLAG_generate_perf_events_symbols || FLAG_generate_perf_jitdump) {
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LOG_INFO(
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"Dual code mapping disabled to generate perf events or jitdump.\n");
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FLAG_dual_map_code = false;
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return;
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}
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#endif
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// Detect dual mapping exec permission limitation on some platforms,
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// such as on docker containers, and disable dual mapping in this case.
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// Also detect for missing support of memfd_create syscall.
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if (FLAG_dual_map_code) {
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intptr_t size = page_size_;
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intptr_t alignment = 256 * 1024; // e.g. heap page size.
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VirtualMemory* vm = AllocateAligned(size, alignment, true, NULL);
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if (vm == NULL) {
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LOG_INFO("memfd_create not supported; disabling dual mapping of code.\n");
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FLAG_dual_map_code = false;
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return;
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}
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void* region = reinterpret_cast<void*>(vm->region_.start());
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void* alias = reinterpret_cast<void*>(vm->alias_.start());
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if (region == alias ||
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mprotect(region, size, PROT_READ) != 0 || // Remove PROT_WRITE.
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mprotect(alias, size, PROT_READ | PROT_EXEC) != 0) { // Add PROT_EXEC.
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LOG_INFO("mprotect fails; disabling dual mapping of code.\n");
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FLAG_dual_map_code = false;
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}
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delete vm;
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}
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#endif // defined(DUAL_MAPPING_SUPPORTED)
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}
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bool VirtualMemory::DualMappingEnabled() {
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return FLAG_dual_map_code;
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}
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static void unmap(uword start, uword end) {
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ASSERT(start <= end);
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uword size = end - start;
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if (size == 0) {
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return;
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}
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if (munmap(reinterpret_cast<void*>(start), size) != 0) {
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int error = errno;
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const int kBufferSize = 1024;
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char error_buf[kBufferSize];
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FATAL2("munmap error: %d (%s)", error,
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Utils::StrError(error, error_buf, kBufferSize));
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}
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}
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#if defined(DUAL_MAPPING_SUPPORTED)
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// Do not leak file descriptors to child processes.
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#if !defined(MFD_CLOEXEC)
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#define MFD_CLOEXEC 0x0001U
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#endif
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// Wrapper to call memfd_create syscall.
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static inline int memfd_create(const char* name, unsigned int flags) {
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#if !defined(__NR_memfd_create)
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errno = ENOSYS;
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return -1;
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#else
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return syscall(__NR_memfd_create, name, flags);
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#endif
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}
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static void* MapAligned(int fd,
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int prot,
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intptr_t size,
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intptr_t alignment,
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intptr_t allocated_size) {
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void* address =
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mmap(NULL, allocated_size, PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
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LOG_INFO("mmap(NULL, 0x%" Px ", PROT_NONE, ...): %p\n", allocated_size,
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address);
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if (address == MAP_FAILED) {
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return NULL;
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}
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const uword base = reinterpret_cast<uword>(address);
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const uword aligned_base = Utils::RoundUp(base, alignment);
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// Guarantee the alignment by mapping at a fixed address inside the above
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// mapping. Overlapping region will be automatically discarded in the above
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// mapping. Manually discard non-overlapping regions.
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address = mmap(reinterpret_cast<void*>(aligned_base), size, prot,
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MAP_SHARED | MAP_FIXED, fd, 0);
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LOG_INFO("mmap(0x%" Px ", 0x%" Px ", %u, ...): %p\n", aligned_base, size,
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prot, address);
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if (address == MAP_FAILED) {
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unmap(base, base + allocated_size);
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return NULL;
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}
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ASSERT(address == reinterpret_cast<void*>(aligned_base));
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unmap(base, aligned_base);
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unmap(aligned_base + size, base + allocated_size);
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return address;
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}
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#endif // defined(DUAL_MAPPING_SUPPORTED)
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VirtualMemory* VirtualMemory::AllocateAligned(intptr_t size,
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intptr_t alignment,
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bool is_executable,
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const char* name) {
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#if defined(TARGET_ARCH_DBC)
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RELEASE_ASSERT(!is_executable);
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#endif
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// When FLAG_write_protect_code is active, code memory (indicated by
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// is_executable = true) is allocated as non-executable and later
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// changed to executable via VirtualMemory::Protect.
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//
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// If FLAG_dual_map_code is active, the executable mapping will be mapped RX
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// immediately and never changes protection until it is eventually unmapped.
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ASSERT(Utils::IsAligned(size, page_size_));
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ASSERT(Utils::IsPowerOfTwo(alignment));
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ASSERT(Utils::IsAligned(alignment, page_size_));
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const intptr_t allocated_size = size + alignment - page_size_;
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#if defined(DUAL_MAPPING_SUPPORTED)
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int fd = -1;
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const bool dual_mapping =
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is_executable && FLAG_write_protect_code && FLAG_dual_map_code;
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if (dual_mapping) {
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fd = memfd_create("dart_vm", MFD_CLOEXEC);
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if (fd == -1) {
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return NULL;
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}
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if (ftruncate(fd, size) == -1) {
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close(fd);
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return NULL;
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}
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const int region_prot = PROT_READ | PROT_WRITE;
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void* region_ptr =
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MapAligned(fd, region_prot, size, alignment, allocated_size);
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if (region_ptr == NULL) {
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close(fd);
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return NULL;
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}
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// The mapping will be RX and stays that way until it will eventually be
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// unmapped.
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MemoryRegion region(region_ptr, size);
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// DUAL_MAPPING_SUPPORTED is false in TARGET_OS_MACOS and hence support
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// for MAP_JIT is not required here.
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const int alias_prot = PROT_READ | PROT_EXEC;
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void* alias_ptr =
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MapAligned(fd, alias_prot, size, alignment, allocated_size);
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close(fd);
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if (alias_ptr == NULL) {
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const uword region_base = reinterpret_cast<uword>(region_ptr);
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unmap(region_base, region_base + size);
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return NULL;
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}
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ASSERT(region_ptr != alias_ptr);
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MemoryRegion alias(alias_ptr, size);
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return new VirtualMemory(region, alias, region);
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}
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#endif // defined(DUAL_MAPPING_SUPPORTED)
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const int prot =
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PROT_READ | PROT_WRITE |
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((is_executable && !FLAG_write_protect_code) ? PROT_EXEC : 0);
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int map_flags = MAP_PRIVATE | MAP_ANONYMOUS;
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#if (defined(HOST_OS_MACOS) && !defined(HOST_OS_IOS))
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if (is_executable && IsAtLeastOS10_14()) {
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map_flags |= MAP_JIT;
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}
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#endif // defined(HOST_OS_MACOS)
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void* address = mmap(NULL, allocated_size, prot, map_flags, -1, 0);
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LOG_INFO("mmap(NULL, 0x%" Px ", %u, ...): %p\n", allocated_size, prot,
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address);
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if (address == MAP_FAILED) {
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return NULL;
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}
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const uword base = reinterpret_cast<uword>(address);
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const uword aligned_base = Utils::RoundUp(base, alignment);
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unmap(base, aligned_base);
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unmap(aligned_base + size, base + allocated_size);
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MemoryRegion region(reinterpret_cast<void*>(aligned_base), size);
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return new VirtualMemory(region, region);
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}
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VirtualMemory::~VirtualMemory() {
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if (vm_owns_region()) {
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unmap(reserved_.start(), reserved_.end());
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const intptr_t alias_offset = AliasOffset();
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if (alias_offset != 0) {
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unmap(reserved_.start() + alias_offset, reserved_.end() + alias_offset);
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}
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}
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}
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void VirtualMemory::FreeSubSegment(void* address,
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intptr_t size) {
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const uword start = reinterpret_cast<uword>(address);
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unmap(start, start + size);
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}
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void VirtualMemory::Protect(void* address, intptr_t size, Protection mode) {
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#if defined(TARGET_ARCH_DBC)
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RELEASE_ASSERT((mode != kReadExecute) && (mode != kReadWriteExecute));
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#endif
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#if defined(DEBUG)
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Thread* thread = Thread::Current();
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ASSERT((thread == nullptr) || thread->IsMutatorThread() ||
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thread->isolate()->mutator_thread()->IsAtSafepoint());
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#endif
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uword start_address = reinterpret_cast<uword>(address);
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uword end_address = start_address + size;
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uword page_address = Utils::RoundDown(start_address, PageSize());
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int prot = 0;
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switch (mode) {
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case kNoAccess:
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prot = PROT_NONE;
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break;
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case kReadOnly:
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prot = PROT_READ;
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break;
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case kReadWrite:
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prot = PROT_READ | PROT_WRITE;
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break;
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case kReadExecute:
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prot = PROT_READ | PROT_EXEC;
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break;
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case kReadWriteExecute:
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prot = PROT_READ | PROT_WRITE | PROT_EXEC;
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break;
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}
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if (mprotect(reinterpret_cast<void*>(page_address),
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end_address - page_address, prot) != 0) {
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int error = errno;
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const int kBufferSize = 1024;
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char error_buf[kBufferSize];
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LOG_INFO("mprotect(0x%" Px ", 0x%" Px ", %u) failed\n", page_address,
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end_address - page_address, prot);
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FATAL2("mprotect error: %d (%s)", error,
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Utils::StrError(error, error_buf, kBufferSize));
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}
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LOG_INFO("mprotect(0x%" Px ", 0x%" Px ", %u) ok\n", page_address,
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end_address - page_address, prot);
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}
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} // namespace dart
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#endif // defined(HOST_OS_ANDROID ... HOST_OS_LINUX ... HOST_OS_MACOS)
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