nickdesaulniers added a comment.
In D126137#3530777 <https://reviews.llvm.org/D126137#3530777>, @kristof.beyls
wrote:
> Therefore, I wonder if it wouldn't be better to name this -mharden-sls=retbr
> for more consistency across architectures?
I think it's best to maintain compatibility with GCC; to do so otherwise might
be surprising for users.
> Or is the indirect function call case not relevant for x86 (sorry - I'm not
> up to speed on the details on the x86 side)?
Looks like GCC does not instrument indirect calls from what I can tell:
$ cat x.c
void bar(void (*x)(void)) {
x();
x();
}
$ gcc -mharden-sls=all x.c -c -O2
$ llvm-objdump -dr x.o
...
0000000000000000 <bar>:
0: 53 pushq %rbx
1: 48 89 fb movq %rdi, %rbx
4: ff d7 callq *%rdi
6: 48 89 d8 movq %rbx, %rax
9: 5b popq %rbx
a: ff e0 jmpq *%rax
c: cc int3
so the indirect `call` instruction is not hardened. The indirect jmp (tail
call) is.
Repository:
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https://reviews.llvm.org/D126137/new/
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