From 7d1a7c0417c0e570c8126b373af76fc2fa609841 Mon Sep 17 00:00:00 2001 From: Dale Johannesen Date: Tue, 15 Sep 2009 18:32:14 +0000 Subject: [PATCH] Change the marker byte for stubs from 0xcd to 0xce (another form of interrupt instruction, which shouldn't arise any other way). 0xcd is also used by JITMemoryManager to initialize the buffer to garbage, which means it could appear following a noreturn call even when that is not a stub, confusing X86CompilationCallback2. PR 4929. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@81888 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Target/X86/X86JITInfo.cpp | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/lib/Target/X86/X86JITInfo.cpp b/lib/Target/X86/X86JITInfo.cpp index 9ea42ac93a3..62ca47ff787 100644 --- a/lib/Target/X86/X86JITInfo.cpp +++ b/lib/Target/X86/X86JITInfo.cpp @@ -338,7 +338,7 @@ X86CompilationCallback2(intptr_t *StackPtr, intptr_t RetAddr) { "Could not find return address on the stack!"); // It's a stub if there is an interrupt marker after the call. - bool isStub = ((unsigned char*)RetAddr)[0] == 0xCD; + bool isStub = ((unsigned char*)RetAddr)[0] == 0xCE; // The call instruction should have pushed the return value onto the stack... #if defined (X86_64_JIT) @@ -377,7 +377,7 @@ X86CompilationCallback2(intptr_t *StackPtr, intptr_t RetAddr) { // If this is a stub, rewrite the call into an unconditional branch // instruction so that two return addresses are not pushed onto the stack // when the requested function finally gets called. This also makes the - // 0xCD byte (interrupt) dead, so the marker doesn't effect anything. + // 0xCE byte (interrupt) dead, so the marker doesn't effect anything. #if defined (X86_64_JIT) // If the target address is within 32-bit range of the stub, use a // PC-relative branch instead of loading the actual address. (This is @@ -480,7 +480,10 @@ void *X86JITInfo::emitFunctionStub(const Function* F, void *Fn, JCE.emitWordLE((intptr_t)Fn-JCE.getCurrentPCValue()-4); #endif - JCE.emitByte(0xCD); // Interrupt - Just a marker identifying the stub! + // This used to use 0xCD, but that value is used by JITMemoryManager to + // initialize the buffer with garbage, which means it may follow a + // noreturn function call, confusing X86CompilationCallback2. PR 4929. + JCE.emitByte(0xCE); // Interrupt - Just a marker identifying the stub! return JCE.finishGVStub(F); } -- 2.34.1