On Tue, 2024-03-05 at 19:19 -0800, Alexei Starovoitov wrote:
> From: Alexei Starovoitov <ast@xxxxxxxxxx>
>
> Use may_goto instruction to implement cond_break macro.
> Ideally the macro should be written as:
> asm volatile goto(".byte 0xe5;
> .byte 0;
> .short %l[l_break] ...
> .long 0;
> but LLVM doesn't recognize fixup of 2 byte PC relative yet.
> Hence use
> asm volatile goto(".byte 0xe5;
> .byte 0;
> .long %l[l_break] ...
> .short 0;
> that produces correct asm on little endian.
>
> Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
Acked-by: Eduard Zingerman <eddyz87@xxxxxxxxx>
I tried rewriting with offset +1 and an additional goto:
({ __label__ l_break, l_continue; \
asm volatile goto("%[jcond]; goto %l[l_break];"\
:: __imm_insn(jcond, BPF_RAW_INSN(BPF_JMP | BPF_JCOND, 0, 0, 1, 0)) \
:: l_break); \
goto l_continue; \
l_break: break; \
l_continue:; \
})
But BPF_RAW_INSN needs filter.h, which can't be included because of vmlinux.h,
unfortunate :(
