ExecutableAllocator.h [plain text]
#ifndef ExecutableAllocator_h
#define ExecutableAllocator_h
#include <limits>
#include <wtf/Assertions.h>
#include <wtf/PassRefPtr.h>
#include <wtf/RefCounted.h>
#include <wtf/UnusedParam.h>
#include <wtf/Vector.h>
#if PLATFORM(IPHONE)
#include <libkern/OSCacheControl.h>
#include <sys/mman.h>
#endif
#define JIT_ALLOCATOR_PAGE_SIZE (ExecutableAllocator::pageSize)
#define JIT_ALLOCATOR_LARGE_ALLOC_SIZE (ExecutableAllocator::pageSize * 4)
#if ENABLE(ASSEMBLER_WX_EXCLUSIVE)
#define PROTECTION_FLAGS_RW (PROT_READ | PROT_WRITE)
#define PROTECTION_FLAGS_RX (PROT_READ | PROT_EXEC)
#define INITIAL_PROTECTION_FLAGS PROTECTION_FLAGS_RX
#else
#define INITIAL_PROTECTION_FLAGS (PROT_READ | PROT_WRITE | PROT_EXEC)
#endif
namespace JSC {
inline size_t roundUpAllocationSize(size_t request, size_t granularity)
{
if ((std::numeric_limits<size_t>::max() - granularity) <= request)
CRASH();
size_t size = request + (granularity - 1);
size = size & ~(granularity - 1);
ASSERT(size >= request);
return size;
}
}
#if ENABLE(ASSEMBLER)
namespace JSC {
class ExecutablePool : public RefCounted<ExecutablePool> {
private:
struct Allocation {
char* pages;
size_t size;
};
typedef Vector<Allocation, 2> AllocationList;
public:
static PassRefPtr<ExecutablePool> create(size_t n)
{
return adoptRef(new ExecutablePool(n));
}
void* alloc(size_t n)
{
ASSERT(m_freePtr <= m_end);
n = roundUpAllocationSize(n, sizeof(void*));
if (static_cast<ptrdiff_t>(n) < (m_end - m_freePtr)) {
void* result = m_freePtr;
m_freePtr += n;
return result;
}
return poolAllocate(n);
}
~ExecutablePool()
{
AllocationList::const_iterator end = m_pools.end();
for (AllocationList::const_iterator ptr = m_pools.begin(); ptr != end; ++ptr)
ExecutablePool::systemRelease(*ptr);
}
size_t available() const { return (m_pools.size() > 1) ? 0 : m_end - m_freePtr; }
private:
static Allocation systemAlloc(size_t n);
static void systemRelease(const Allocation& alloc);
ExecutablePool(size_t n);
void* poolAllocate(size_t n);
char* m_freePtr;
char* m_end;
AllocationList m_pools;
};
class ExecutableAllocator {
enum ProtectionSeting { Writable, Executable };
public:
static size_t pageSize;
ExecutableAllocator()
{
if (!pageSize)
intializePageSize();
m_smallAllocationPool = ExecutablePool::create(JIT_ALLOCATOR_LARGE_ALLOC_SIZE);
}
PassRefPtr<ExecutablePool> poolForSize(size_t n)
{
if (n < m_smallAllocationPool->available())
return m_smallAllocationPool;
if (n > JIT_ALLOCATOR_LARGE_ALLOC_SIZE)
return ExecutablePool::create(n);
RefPtr<ExecutablePool> pool = ExecutablePool::create(JIT_ALLOCATOR_LARGE_ALLOC_SIZE);
if ((pool->available() - n) > m_smallAllocationPool->available())
m_smallAllocationPool = pool;
return pool.release();
}
#if ENABLE(ASSEMBLER_WX_EXCLUSIVE) || !(PLATFORM(X86) || PLATFORM(X86_64))
static void makeWritable(void* start, size_t size)
{
reprotectRegion(start, size, Writable);
}
static void makeExecutable(void* start, size_t size)
{
reprotectRegion(start, size, Executable);
cacheFlush(start, size);
}
class MakeWritable {
public:
MakeWritable(void* start, size_t size)
: m_start(start)
, m_size(size)
{
makeWritable(start, size);
}
~MakeWritable()
{
makeExecutable(m_start, m_size);
}
private:
void* m_start;
size_t m_size;
};
#else
static void makeWritable(void*, size_t) {}
static void makeExecutable(void*, size_t) {}
class MakeWritable { public: MakeWritable(void*, size_t) {} };
#endif
private:
#if ENABLE(ASSEMBLER_WX_EXCLUSIVE) || !(PLATFORM(X86) || PLATFORM(X86_64))
#if ENABLE(ASSEMBLER_WX_EXCLUSIVE)
static void reprotectRegion(void*, size_t, ProtectionSeting);
#else
static void reprotectRegion(void*, size_t, ProtectionSeting) {}
#endif
static void cacheFlush(void* code, size_t size)
{
#if PLATFORM(X86) || PLATFORM(X86_64)
UNUSED_PARAM(code);
UNUSED_PARAM(size);
#elif PLATFORM_ARM_ARCH(7) && PLATFORM(IPHONE)
sys_dcache_flush(code, size);
sys_icache_invalidate(code, size);
#else
#error "ExecutableAllocator::cacheFlush not implemented on this platform."
#endif
}
#endif
RefPtr<ExecutablePool> m_smallAllocationPool;
static void intializePageSize();
};
inline ExecutablePool::ExecutablePool(size_t n)
{
size_t allocSize = roundUpAllocationSize(n, JIT_ALLOCATOR_PAGE_SIZE);
Allocation mem = systemAlloc(allocSize);
m_pools.append(mem);
m_freePtr = mem.pages;
if (!m_freePtr)
CRASH(); m_end = m_freePtr + allocSize;
}
inline void* ExecutablePool::poolAllocate(size_t n)
{
size_t allocSize = roundUpAllocationSize(n, JIT_ALLOCATOR_PAGE_SIZE);
Allocation result = systemAlloc(allocSize);
if (!result.pages)
CRASH();
ASSERT(m_end >= m_freePtr);
if ((allocSize - n) > static_cast<size_t>(m_end - m_freePtr)) {
m_freePtr = result.pages + n;
m_end = result.pages + allocSize;
}
m_pools.append(result);
return result.pages;
}
}
#endif // ENABLE(ASSEMBLER)
#endif // !defined(ExecutableAllocator)