Re: [PATCH bpf-next v3 2/3] selftests/bpf: add cmp_map_pointer_with_const test

[Ihor Solodrai <ihor.solodrai@linux.dev>]

On 6/5/25 9:20 AM, Andrii Nakryiko wrote:
> On Wed, Jun 4, 2025 at 3:28 PM Ihor Solodrai <isolodrai@meta.com> wrote:
>>
>> Add a test for CONST_PTR_TO_MAP comparison with a non-0 constant. A
>> BPF program with this code must not pass verification in unpriv.
>>
>> Signed-off-by: Ihor Solodrai <isolodrai@meta.com>
>> ---
>>   .../selftests/bpf/progs/verifier_unpriv.c       | 17 +++++++++++++++++
>>   1 file changed, 17 insertions(+)
>>
>> diff --git a/tools/testing/selftests/bpf/progs/verifier_unpriv.c b/tools/testing/selftests/bpf/progs/verifier_unpriv.c
>> index 28200f068ce5..c4a48b57e167 100644
>> --- a/tools/testing/selftests/bpf/progs/verifier_unpriv.c
>> +++ b/tools/testing/selftests/bpf/progs/verifier_unpriv.c
>> @@ -634,6 +634,23 @@ l0_%=:     r0 = 0;                                         \
>>          : __clobber_all);
>>   }
>>
>> +SEC("socket")
>> +__description("unpriv: cmp map pointer with const")
>> +__success __failure_unpriv __msg_unpriv("R1 pointer comparison prohibited")
>> +__retval(0)
>> +__naked void cmp_map_pointer_with_const(void)
>> +{
>> +       asm volatile ("                                 \
>> +       r1 = 0;                                         \
> 
> Does this assignment serve any purpose?

I don't think so. This was copypasted from
cmp_map_pointer_with_zero. I'll try removing in both.

> 
>> +       r1 = %[map_hash_8b] ll;                         \
>> +       if r1 == 0xdeadbeef goto l0_%=;         \
>> +l0_%=: r0 = 0;                                         \
>> +       exit;                                           \
>> +"      :
>> +       : __imm_addr(map_hash_8b)
>> +       : __clobber_all);
>> +}
>> +
>>   SEC("socket")
>>   __description("unpriv: write into frame pointer")
>>   __failure __msg("frame pointer is read only")
>> --
>> 2.47.1
>>