On Thu, Dec 03, 2020 at 09:27:04PM -0800, Yonghong Song wrote:
> On 12/3/20 8:02 AM, Brendan Jackman wrote:
[...]
> > diff --git a/kernel/bpf/disasm.c b/kernel/bpf/disasm.c
> > index 37c8d6e9b4cc..3ee2246a52ef 100644
> > --- a/kernel/bpf/disasm.c
> > +++ b/kernel/bpf/disasm.c
> > @@ -160,6 +160,13 @@ void print_bpf_insn(const struct bpf_insn_cbs *cbs,
> > bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
> > insn->dst_reg, insn->off,
> > insn->src_reg);
> > + } else if (BPF_MODE(insn->code) == BPF_ATOMIC &&
> > + insn->imm == (BPF_ADD | BPF_FETCH)) {
> > + verbose(cbs->private_data, "(%02x) r%d =
> > atomic%s_fetch_add(*(%s *)(r%d %+d), r%d)\n",
>
> We should not do dereference here (withough first *), right? since the input
> is actually an address. something like below?
> r2 = atomic[64]_fetch_add((u64/u32 *)(r3 +40), r2)
Ah yep - thanks!
[...]
> > diff --git a/tools/include/linux/filter.h b/tools/include/linux/filter.h
> > index 95ff51d97f25..ac7701678e1a 100644
> > --- a/tools/include/linux/filter.h
> > +++ b/tools/include/linux/filter.h
> > @@ -180,6 +180,16 @@
> > .imm = BPF_ADD })
> > #define BPF_STX_XADD BPF_ATOMIC_ADD /* alias */
> > +/* Atomic memory add with fetch, src_reg = atomic_fetch_add(*(dst_reg +
> > off), src_reg); */
>
> Maybe src_reg = atomic_fetch_add(dst_reg + off, src_reg)?
Yep - and the same for the bitwise ops in the later patch.
