Re: [PATCH bpf-next v2 09/15] selftests/bpf: Test assigning ID to scalars on spill

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



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
>





[Index of Archives]     [Linux Wireless]     [Linux Kernel]     [ATH6KL]     [Linux Bluetooth]     [Linux Netdev]     [Kernel Newbies]     [Share Photos]     [IDE]     [Security]     [Git]     [Netfilter]     [Bugtraq]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Linux ATA RAID]     [Samba]     [Device Mapper]

  Powered by Linux