On 5/10/24 16:29, Eduard Zingerman wrote:
On Fri, 2024-05-10 at 16:17 -0700, Eduard Zingerman wrote:
On Fri, 2024-05-10 at 16:04 -0700, Kui-Feng Lee wrote:
[...]
I am not sure if I read you question correctly.
For example, we have 3 correct info.
[info(offset=0x8), info(offset=0x10), info(offset=0x18)]
And We have program that includes 3 instructions to access the offset
0x8, 0x10, and 0x18. (let's assume these load instructions would be
checked against infos)
load r1, [0x8]
load r1, [0x10]
load r1, [0x18]
If everything works as expected, the verifier would accept the program.
Otherwise, like you said, all 3 info are pointing to the same offset.
[info(0offset=0x8), info(offset=0x8), info(offset=0x8)]
Then, the later two instructions should fail the check.
Ok, what you are saying is possible not with load but with some kfunc
that accepts a special pointer. E.g. when verifier.c:check_kfunc_args()
expects an argument of KF_ARG_PTR_TO_LIST_HEAD type it would report an
error if special field is not found.
So the structure of the test would be:
- define a nested data structure with list head at some leafs;
- in the BPF program call a kfunc accessing each of the list heads;
- if all offsets are computed correctly there would be no load time error;
- this is a load time test, no need to actually run the BPF program.
[...]
Yes, that is what I meant.
Sorry for replying late.
