On 7/27/19 11:24 AM, Andrii Nakryiko wrote:
> On Sat, Jul 27, 2019 at 10:00 AM Alexei Starovoitov <ast@xxxxxx> wrote:
>>
>> On 7/26/19 11:25 PM, Andrii Nakryiko wrote:
>>>>> + } else if (class == BPF_ST && BPF_MODE(insn->code) == BPF_MEM) {
>>>>> + if (insn->imm != orig_off)
>>>>> + return -EINVAL;
>>>>> + insn->imm = new_off;
>>>>> + pr_debug("prog '%s': patched insn #%d (ST | MEM) imm %d -> %d\n",
>>>>> + bpf_program__title(prog, false),
>>>>> + insn_idx, orig_off, new_off);
>>>> I'm pretty sure llvm was not capable of emitting BPF_ST insn.
>>>> When did that change?
>>> I just looked at possible instructions that could have 32-bit
>>> immediate value. This is `*(rX) = offsetof(struct s, field)`, which I
>>> though is conceivable. Do you think I should drop it?
>>
>> Just trying to point out that since it's not emitted by llvm
>> this code is likely untested ?
>> Or you've created a bpf asm test for this?
>
>
> Yeah, it's untested right now. Let me try to come up with LLVM
> assembly + relocation (not yet sure how/whether builtin works with
> inline assembly), if that works out, I'll leave this, if not, I'll
> drop BPF_ST|BPF_MEM part.
FYI. The llvm does not have assembly code format for BPF_ST instructions
as it does not generate code for it. So inline asm through llvm won't
work. llvm disasseembler won't be able to decode BPF_ST either.
>>
>>
