[llvm-dev] What's definition to type of function in -fsanitize=cfi-icall in llvm/clang 7? (original) (raw)

Chandler Carruth via llvm-dev llvm-dev at lists.llvm.org
Fri Jan 25 01:56:14 PST 2019

+Peter Collingbourne <pcc at google.com>

On Thu, Jan 24, 2019 at 5:30 PM PenYiWang via llvm-dev < llvm-dev at lists.llvm.org> wrote:

Hi

I learn llvm/clang cfi from this repo and also the usenix '14 paper. https://github.com/trailofbits/clang-cfi-showcase/blob/master/cfiicall.c As usenix '14 paper says, the type of functoin is determined only by number of argument. But I try in llvm/clang 7, I found that it is getting complicated. For example, #include<stdio.h> int func(int a,float b,char c){ printf("hi %d,%f,%c\n",a,b,c); return a+1; } int main(){ int (*fp)(int,float,char); fp = func; fp(1,1.0,'c'); return 0; } clang -flto -fsanitize=cfi -fvisibility=hidden -O0 ./test.c And the use objdump to see the executable : 00000000004005a0 <_typeid_ZTSFiifcEglobaladdr>: 4005a0: e9 4b ff ff ff jmpq 4004f0 <func.cfi> 4005a5: cc int3 4005a6: cc int3 4005a7: cc int3 4005a8: 0f 1f 84 00 00 00 00 nopl 0x0(%rax,%rax,1) 4005af: 00 From the type id mangling "iifc", I can guess that the type of return value and the type of every argument are the factors to determine the type of a function. I wonder that what's the definition of type of a function in llvm/clang 7. Is there any document I can study? Or I should study the code in compiler fronted (clang)? Thank you.

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