JitCode*
Linker::newCode(JSContext* cx, CodeKind kind)
{
JS::AutoAssertNoGC nogc(cx);
if (masm.oom())
return fail(cx);
masm.performPendingReadBarriers();
static const size_t ExecutableAllocatorAlignment = sizeof(void*);
static_assert(CodeAlignment >= ExecutableAllocatorAlignment,
"Unexpected alignment requirements");
// We require enough bytes for the code, header, and worst-case alignment padding.
size_t bytesNeeded = masm.bytesNeeded() +
sizeof(JitCodeHeader) +
(CodeAlignment - ExecutableAllocatorAlignment);
if (bytesNeeded >= MAX_BUFFER_SIZE)
return fail(cx);
// ExecutableAllocator requires bytesNeeded to be aligned.
bytesNeeded = AlignBytes(bytesNeeded, ExecutableAllocatorAlignment);
ExecutablePool* pool;
uint8_t* result =
(uint8_t*)cx->runtime()->jitRuntime()->execAlloc().alloc(cx, bytesNeeded, &pool, kind);
if (!result)
return fail(cx);
// The JitCodeHeader will be stored right before the code buffer.
uint8_t* codeStart = result + sizeof(JitCodeHeader);
// Bump the code up to a nice alignment.
codeStart = (uint8_t*)AlignBytes((uintptr_t)codeStart, CodeAlignment);
MOZ_ASSERT(codeStart + masm.bytesNeeded() <= result + bytesNeeded);
uint32_t headerSize = codeStart - result;
JitCode* code = JitCode::New<NoGC>(cx, codeStart, bytesNeeded - headerSize,
headerSize, pool, kind);
if (!code)
return fail(cx);
if (masm.oom())
return fail(cx);
awjc.emplace(result, bytesNeeded);
code->copyFrom(masm);
masm.link(code);
if (masm.embedsNurseryPointers())
cx->runtime()->gc.storeBuffer().putWholeCell(code);
return code;
}
static void*
MapAlignedPagesSlow(size_t size, size_t alignment)
{
/*
* Windows requires that there be a 1:1 mapping between VM allocation
* and deallocation operations. Therefore, take care here to acquire the
* final result via one mapping operation. This means unmapping any
* preliminary result that is not correctly aligned.
*/
void* p;
do {
/*
* Over-allocate in order to map a memory region that is definitely
* large enough, then deallocate and allocate again the correct size,
* within the over-sized mapping.
*
* Since we're going to unmap the whole thing anyway, the first
* mapping doesn't have to commit pages.
*/
size_t reserveSize = size + alignment - pageSize;
p = MapMemory(reserveSize, MEM_RESERVE);
if (!p)
return nullptr;
void* chunkStart = (void*)AlignBytes(uintptr_t(p), alignment);
UnmapPages(p, reserveSize);
p = MapMemoryAt(chunkStart, size, MEM_COMMIT | MEM_RESERVE);
/* Failure here indicates a race with another thread, so try again. */
} while (!p);
return p;
}
JitCode*
Linker::newCode(JSContext* cx, CodeKind kind, bool hasPatchableBackedges /* = false */)
{
MOZ_ASSERT(masm.numAsmJSAbsoluteAddresses() == 0);
MOZ_ASSERT_IF(hasPatchableBackedges, kind == ION_CODE);
gc::AutoSuppressGC suppressGC(cx);
if (masm.oom())
return fail(cx);
ExecutablePool* pool;
size_t bytesNeeded = masm.bytesNeeded() + sizeof(JitCode*) + CodeAlignment;
if (bytesNeeded >= MAX_BUFFER_SIZE)
return fail(cx);
// ExecutableAllocator requires bytesNeeded to be word-size aligned.
bytesNeeded = AlignBytes(bytesNeeded, sizeof(void*));
ExecutableAllocator& execAlloc = hasPatchableBackedges
? cx->runtime()->jitRuntime()->backedgeExecAlloc()
: cx->runtime()->jitRuntime()->execAlloc();
uint8_t* result = (uint8_t*)execAlloc.alloc(bytesNeeded, &pool, kind);
if (!result)
return fail(cx);
// The JitCode pointer will be stored right before the code buffer.
uint8_t* codeStart = result + sizeof(JitCode*);
// Bump the code up to a nice alignment.
codeStart = (uint8_t*)AlignBytes((uintptr_t)codeStart, CodeAlignment);
uint32_t headerSize = codeStart - result;
JitCode* code = JitCode::New<allowGC>(cx, codeStart, bytesNeeded - headerSize,
headerSize, pool, kind);
if (!code)
return nullptr;
if (masm.oom())
return fail(cx);
awjc.emplace(result, bytesNeeded);
code->copyFrom(masm);
masm.link(code);
if (masm.embedsNurseryPointers())
cx->runtime()->gc.storeBuffer.putWholeCell(code);
return code;
}