Changeset 44341 in webkit for trunk/JavaScriptCore/jit/ExecutableAllocatorPosix.cpp

Timestamp:

Jun 1, 2009, 6:20:35 PM (16 years ago)

Author:

[email protected]

Message:

2009-06-01 Gavin Barraclough <​[email protected]>

Reviewed by Sam "WX" Weinig.

Allow the JIT to operate without relying on use of RWX memory, on platforms where this is supported.

This patch adds a switch to Platform.h (ENABLE_ASSEMBLER_WX_EXCLUSIVE) which enables this mode of operation.
When this flag is set, all executable memory will be allocated RX, and switched to RW only whilst being
modified. Upon completion of code generation the protection is switched back to RX to allow execution.

Further optimization will be required before it is desirable to enable this mode of operation by default;
enabling this presently incurs a 5%-10% regression.

(Submitting disabled - no performance impact).

• assembler/AbstractMacroAssembler.h: (JSC::AbstractMacroAssembler::CodeLocationInstruction::repatchLoadToLEA): (JSC::AbstractMacroAssembler::CodeLocationLabel::fromFunctionPointer): (JSC::AbstractMacroAssembler::CodeLocationJump::relink): (JSC::AbstractMacroAssembler::CodeLocationCall::relink): (JSC::AbstractMacroAssembler::CodeLocationNearCall::relink): (JSC::AbstractMacroAssembler::CodeLocationDataLabel32::repatch): (JSC::AbstractMacroAssembler::CodeLocationDataLabelPtr::repatch): (JSC::AbstractMacroAssembler::ProcessorReturnAddress::relinkCallerToTrampoline): (JSC::AbstractMacroAssembler::ProcessorReturnAddress::relinkCallerToFunction): (JSC::AbstractMacroAssembler::ProcessorReturnAddress::relinkNearCallerToTrampoline): (JSC::AbstractMacroAssembler::ProcessorReturnAddress::relinkNearCallerToFunction): (JSC::AbstractMacroAssembler::PatchBuffer::PatchBuffer): (JSC::AbstractMacroAssembler::PatchBuffer::~PatchBuffer): (JSC::AbstractMacroAssembler::PatchBuffer::link): (JSC::AbstractMacroAssembler::PatchBuffer::patch): (JSC::AbstractMacroAssembler::PatchBuffer::performFinalization): (JSC::::CodeLocationCommon::nearCallAtOffset): (JSC::::CodeLocationCall::CodeLocationCall): (JSC::::CodeLocationNearCall::CodeLocationNearCall):
• assembler/AssemblerBuffer.h: (JSC::AssemblerBuffer::executableCopy):
• assembler/X86Assembler.h: (JSC::CAN_SIGN_EXTEND_U32_64): (JSC::X86Assembler::linkJump): (JSC::X86Assembler::linkCall): (JSC::X86Assembler::patchPointer): (JSC::X86Assembler::relinkJump): (JSC::X86Assembler::relinkCall): (JSC::X86Assembler::repatchInt32): (JSC::X86Assembler::repatchPointer): (JSC::X86Assembler::repatchLoadToLEA): (JSC::X86Assembler::patchInt32): (JSC::X86Assembler::patchRel32):
• jit/ExecutableAllocator.h: (JSC::ExecutableAllocator::): (JSC::ExecutableAllocator::makeWritable): (JSC::ExecutableAllocator::makeExecutable):
• jit/ExecutableAllocatorFixedVMPool.cpp: (JSC::FixedVMPoolAllocator::FixedVMPoolAllocator):
• jit/ExecutableAllocatorPosix.cpp: (JSC::ExecutablePool::systemAlloc): (JSC::ExecutablePool::systemRelease): (JSC::ExecutableAllocator::reprotectRegion):
• jit/ExecutableAllocatorWin.cpp:
• jit/JITPropertyAccess.cpp: (JSC::JIT::patchGetByIdSelf): (JSC::JIT::patchPutByIdReplace):
• wtf/Platform.h:

File:

• trunk/JavaScriptCore/jit/ExecutableAllocatorPosix.cpp (modified) (4 diffs)

trunk/JavaScriptCore/jit/ExecutableAllocatorPosix.cpp

@@ -28 +28 @@
 #include "ExecutableAllocator.h"
 
-#if ENABLE(ASSEMBLER) && !(PLATFORM(MAC) && PLATFORM(X86_64))
+#if ENABLE(ASSEMBLER)
 
 #include <sys/mman.h>
@@ -35 +35 @@
 
 namespace JSC {
+
+#if !(PLATFORM(MAC) && PLATFORM(X86_64))
 
 void ExecutableAllocator::intializePageSize()
@@ -43 +45 @@
 ExecutablePool::Allocation ExecutablePool::systemAlloc(size_t n)
 {
-    ExecutablePool::Allocation alloc = { reinterpret_cast<char*>(mmap(NULL, n, PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE | MAP_ANON, VM_TAG_FOR_EXECUTABLEALLOCATOR_MEMORY, 0)), n };
+    ExecutablePool::Allocation alloc = { reinterpret_cast<char*>(mmap(NULL, n, INITIAL_PROTECTION_FLAGS, MAP_PRIVATE | MAP_ANON, VM_TAG_FOR_EXECUTABLEALLOCATOR_MEMORY, 0)), n };
     return alloc;
 }
 
-void ExecutablePool::systemRelease(const ExecutablePool::Allocation& alloc) 
+void ExecutablePool::systemRelease(const ExecutablePool::Allocation& alloc)
 { 
     int result = munmap(alloc.pages, alloc.size);
@@ -53 +55 @@
 }
 
+#endif // !(PLATFORM(MAC) && PLATFORM(X86_64))
+
+#if ENABLE(ASSEMBLER_WX_EXCLUSIVE)
+void ExecutableAllocator::reprotectRegion(void* start, size_t size, ProtectionSeting setting)
+{
+    if (!pageSize)
+        intializePageSize();
+
+    // Calculate the start of the page containing this region,
+    // and account for this extra memory within size.
+    intptr_t startPtr = reinterpret_cast<intptr_t>(start);
+    intptr_t pageStartPtr = startPtr & ~(pageSize - 1);
+    void* pageStart = reinterpret_cast<void*>(pageStartPtr);
+    size += (startPtr - pageStartPtr);
+
+    // Round size up
+    size += (pageSize - 1);
+    size &= ~(pageSize - 1);
+
+    mprotect(pageStart, size, (setting == Writable) ? PROTECTION_FLAGS_RW : PROTECTION_FLAGS_RX);
+}
+#endif
+
 }