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?
> 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);
> }
>
