On Fri, Jan 20, 2023 at 11:50:41AM IST, Alexei Starovoitov wrote:
> On Fri, Jan 20, 2023 at 09:13:11AM +0530, Kumar Kartikeya Dwivedi wrote:
> > +
> > +SEC("?tc")
> > +__failure __msg("cannot overwrite referenced dynptr") __log_level(2)
> > +int dynptr_pruning_overwrite(struct __sk_buff *ctx)
> > +{
> > + asm volatile (
> > + "r9 = 0xeB9F;"
> > + "r6 = %[ringbuf] ll;"
> > + "r1 = r6;"
> > + "r2 = 8;"
> > + "r3 = 0;"
> > + "r4 = r10;"
> > + "r4 += -16;"
> > + "call %[bpf_ringbuf_reserve_dynptr];"
> > + "if r0 == 0 goto pjmp1;"
> > + "goto pjmp2;"
> > + "pjmp1:"
> > + "*(u64 *)(r10 - 16) = r9;"
> > + "pjmp2:"
> > + "r1 = r10;"
> > + "r1 += -16;"
> > + "r2 = 0;"
> > + "call %[bpf_ringbuf_discard_dynptr];"
>
> It should still work if we remove "" from every line, right?
> Would it be easier to read?
You mean write it like this?
asm volatile (
"r9 = 0xeB9F; \
r6 = %[ringbuf] ll; \
r1 = r6; \
r2 = 8; \
r3 = 0; \
r4 = r10; \
r4 += -16; \
call %[bpf_ringbuf_reserve_dynptr]; \
if r0 == 0 goto pjmp1; \
goto pjmp2; \
pjmp1: \
*(u64 *)(r10 - 16) = r9; \
pjmp2: \
r1 = r10; \
r1 += -16; \
r2 = 0; \
call %[bpf_ringbuf_discard_dynptr]; "
:
: __imm(bpf_ringbuf_reserve_dynptr),
__imm(bpf_ringbuf_discard_dynptr),
__imm_addr(ringbuf)
: __clobber_all
);
I guess that does look a bit cleaner, if you think the same I can try converting
them.
