On Thu, 04 Jan 2024 at 04:27:00 +0200, Eduard Zingerman wrote:
> On Wed, 2023-12-20 at 23:40 +0200, Maxim Mikityanskiy wrote:
>
> [...]
>
> The two tests below were added by the following commit:
> ef979017b837 ("bpf: selftest: Add verifier tests for <8-byte scalar spill and refill")
>
> As far as I understand, the original intent was to check the behavior
> for stack read/write with non-matching size.
> I think these tests are redundant after patch #13. Wdyt?
_6_offset_to_skb_data is for sure not redundant. I don't test a partial
fill from the most significant bits in my patch 13.
u16_offset_to_skb_data is somewhat similar to
fill_32bit_after_spill_64bit, but they aren't exactly the same: the
former spills (u32)20 and fills (u16)20 (the same value), while my test
spills (u64)0xXXXXXXXX00000000 and fills (u32)0 (the most significant
bits are stripped). Maybe u16_offset_to_skb_data is redundant, but more
coverage is better than less coverage, isn't it?
> > diff --git a/tools/testing/selftests/bpf/progs/verifier_spill_fill.c b/tools/testing/selftests/bpf/progs/verifier_spill_fill.c
> > index 809a09732168..de03e72e07a9 100644
> > --- a/tools/testing/selftests/bpf/progs/verifier_spill_fill.c
> > +++ b/tools/testing/selftests/bpf/progs/verifier_spill_fill.c
> > @@ -217,7 +217,7 @@ __naked void uninit_u32_from_the_stack(void)
> >
> > SEC("tc")
> > __description("Spill a u32 const scalar. Refill as u16. Offset to skb->data")
> > -__failure __msg("invalid access to packet")
> > +__success __retval(0)
> > __naked void u16_offset_to_skb_data(void)
> > {
> > asm volatile (" \
> > @@ -225,19 +225,24 @@ __naked void u16_offset_to_skb_data(void)
> > r3 = *(u32*)(r1 + %[__sk_buff_data_end]); \
> > w4 = 20; \
> > *(u32*)(r10 - 8) = r4; \
> > - r4 = *(u16*)(r10 - 8); \
> > + r4 = *(u16*)(r10 - %[offset]); \
> > r0 = r2; \
> > - /* r0 += r4 R0=pkt R2=pkt R3=pkt_end R4=umax=65535 */\
> > + /* r0 += r4 R0=pkt R2=pkt R3=pkt_end R4=20 */\
> > r0 += r4; \
> > - /* if (r0 > r3) R0=pkt,umax=65535 R2=pkt R3=pkt_end R4=umax=65535 */\
> > + /* if (r0 > r3) R0=pkt,off=20 R2=pkt R3=pkt_end R4=20 */\
> > if r0 > r3 goto l0_%=; \
> > - /* r0 = *(u32 *)r2 R0=pkt,umax=65535 R2=pkt R3=pkt_end R4=20 */\
> > + /* r0 = *(u32 *)r2 R0=pkt,off=20 R2=pkt R3=pkt_end R4=20 */\
> > r0 = *(u32*)(r2 + 0); \
> > l0_%=: r0 = 0; \
> > exit; \
> > " :
> > : __imm_const(__sk_buff_data, offsetof(struct __sk_buff, data)),
> > - __imm_const(__sk_buff_data_end, offsetof(struct __sk_buff, data_end))
> > + __imm_const(__sk_buff_data_end, offsetof(struct __sk_buff, data_end)),
> > +#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
> > + __imm_const(offset, 8)
> > +#else
> > + __imm_const(offset, 6)
> > +#endif
> > : __clobber_all);
> > }
> >
> > @@ -270,7 +275,7 @@ l0_%=: r0 = 0; \
> > }
> >
> > SEC("tc")
> > -__description("Spill a u32 const scalar. Refill as u16 from fp-6. Offset to skb->data")
> > +__description("Spill a u32 const scalar. Refill as u16 from MSB. Offset to skb->data")
> > __failure __msg("invalid access to packet")
> > __naked void _6_offset_to_skb_data(void)
> > {
> > @@ -279,7 +284,7 @@ __naked void _6_offset_to_skb_data(void)
> > r3 = *(u32*)(r1 + %[__sk_buff_data_end]); \
> > w4 = 20; \
> > *(u32*)(r10 - 8) = r4; \
> > - r4 = *(u16*)(r10 - 6); \
> > + r4 = *(u16*)(r10 - %[offset]); \
> > r0 = r2; \
> > /* r0 += r4 R0=pkt R2=pkt R3=pkt_end R4=umax=65535 */\
> > r0 += r4; \
> > @@ -291,7 +296,12 @@ l0_%=: r0 = 0; \
> > exit; \
> > " :
> > : __imm_const(__sk_buff_data, offsetof(struct __sk_buff, data)),
> > - __imm_const(__sk_buff_data_end, offsetof(struct __sk_buff, data_end))
> > + __imm_const(__sk_buff_data_end, offsetof(struct __sk_buff, data_end)),
> > +#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
> > + __imm_const(offset, 6)
> > +#else
> > + __imm_const(offset, 8)
> > +#endif
> > : __clobber_all);
> > }
> >
>
>
>
