On Mon, Jan 8, 2024 at 12:53 PM Maxim Mikityanskiy <maxtram95@xxxxxxxxx> wrote:
>
> From: Maxim Mikityanskiy <maxim@xxxxxxxxxxxxx>
>
> The previous commit implemented assigning IDs to registers holding
> scalars before spill. Add the test cases to check the new functionality.
>
> Signed-off-by: Maxim Mikityanskiy <maxim@xxxxxxxxxxxxx>
> Acked-by: Eduard Zingerman <eddyz87@xxxxxxxxx>
> ---
> .../selftests/bpf/progs/verifier_spill_fill.c | 133 ++++++++++++++++++
> 1 file changed, 133 insertions(+)
>
> diff --git a/tools/testing/selftests/bpf/progs/verifier_spill_fill.c b/tools/testing/selftests/bpf/progs/verifier_spill_fill.c
> index f303ac19cf41..b05aab925ee5 100644
> --- a/tools/testing/selftests/bpf/progs/verifier_spill_fill.c
> +++ b/tools/testing/selftests/bpf/progs/verifier_spill_fill.c
> @@ -766,4 +766,137 @@ l0_%=: r0 = 0; \
> : __clobber_all);
> }
>
[...]
> +
> +SEC("xdp")
> +__description("8-bit spill of 8-bit reg should assign ID")
> +__success __retval(0)
> +__naked void spill_8bit_of_8bit_ok(void)
> +{
> + asm volatile (" \
> + /* Roll one bit to make the register inexact. */\
> + call %[bpf_get_prandom_u32]; \
> + r0 &= 0x80; \
> + /* 8-bit spill r0 to stack - should assign an ID. */\
> + *(u8*)(r10 - 8) = r0; \
> + /* 8-bit fill r1 from stack - should preserve the ID. */\
> + r1 = *(u8*)(r10 - 8); \
> + /* Compare r1 with another register to trigger find_equal_scalars.\
> + * Having one random bit is important here, otherwise the verifier cuts\
> + * the corners. \
> + */ \
> + r2 = 0; \
> + if r1 != r2 goto l0_%=; \
> + /* The result of this comparison is predefined. */\
> + if r0 == r2 goto l0_%=; \
> + /* Dead branch: the verifier should prune it. Do an invalid memory\
> + * access if the verifier follows it. \
> + */ \
> + r0 = *(u64*)(r9 + 0); \
> + exit; \
> +l0_%=: r0 = 0; \
> + exit; \
> +" :
> + : __imm(bpf_get_prandom_u32)
> + : __clobber_all);
> +}
> +
Can you add a test where we spill register of one size and fill a
different size? And what should the behavior be? Should we or should
we not preserve linked IDs in such situation?
> char _license[] SEC("license") = "GPL";
> --
> 2.43.0
>
