On Fri, Dec 13, 2024 at 7:13 PM Eduard Zingerman <eddyz87@xxxxxxxxx> wrote: > > On Fri, 2024-12-13 at 19:44 -0700, Daniel Xu wrote: > > [...] > > > > > + /* First handle precisely tracked STACK_ZERO, up to BPF_REG_SIZE */ > > > > + stype = state->stack[spi].slot_type; > > > > + for (i = 0; i < BPF_REG_SIZE && stype[i] == STACK_ZERO; i++) > > > > > > it's Friday and I'm lazy, but please double-check that this works for > > > both big-endian and little-endian :) > > > > Any tips? Are the existing tests running thru s390x hosts in CI > > sufficient or should I add some tests writen in C (and not BPF > > assembler)? I can never think about endianness correctly... > > I think that if test operates on a key like: > > valid key 15 > v > 0000000f <-- written to stack as a single u64 value > ^^^^^^^ > stack zero marks > > and is executed (e.g. using __retval annotation), > then CI passing for s390 should be enough. +1, something like that where for big-endian it will be all zero while for little endian it would be 0xf (and then make sure that the test should *fail* by making sure that 0xf is not a valid index, so NULL check is necessary) > > There is a guide on how to gen a s390 environment locally: > https://docs.kernel.org/bpf/s390.html > I used it recently to build a vmlinux for s390 with no or minimal > issues. Used it to boot long time ago, but don't remember if there > were any surprises. > > > > with Eduard's suggestion this also becomes interesting when you have > > > 000mmm mix (as one example), because that gives you a small range, and > > > all values might be valid keys for arrays > > > > Can you define what "small range" means? What range is there with 0's? > > Any pointers would be helpful. > > I think Andrii means that each 'm' adds 8 bits of range. > E.g. range for 0000_000m is 0-255, range for 0000_00mm is 0-65535, etc. yes, exactly, thank you, Eduard! > > [...] >
