[llvm-dev] What's definition to type of function in -fsanitize=cfi-icall in llvm/clang 7?
PenYiWang via llvm-dev
llvm-dev at lists.llvm.org
Thu Jan 24 17:30:20 PST 2019
Hi
I learn llvm/clang cfi from this repo and also the usenix '14 paper.
https://github.com/trailofbits/clang-cfi-showcase/blob/master/cfi_icall.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__ZTSFiifcE_global_addr>:
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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