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. [...]
