January 28, 2025 at 5:06 PM, "Eduard Zingerman" <eddyz87@xxxxxxxxx> wrote:
>
> On Sat, 2025-01-25 at 02:19 +0000, Peilin Ye wrote:
>
> >
> > Add several ./test_progs tests:
> >
> >
> >
> > - atomics/load_acquire
> >
> > - atomics/store_release
> >
> > - arena_atomics/load_acquire
> >
> > - arena_atomics/store_release
> >
> > - verifier_load_acquire/*
> >
> > - verifier_store_release/*
> >
> > - verifier_precision/bpf_load_acquire
> >
> > - verifier_precision/bpf_store_release
> >
> >
> >
> > The last two tests are added to check if backtrack_insn() handles the
> >
> > new instructions correctly.
> >
> >
> >
> > Additionally, the last test also makes sure that the verifier
> >
> > "remembers" the value (in src_reg) we store-release into e.g. a stack
> >
> > slot. For example, if we take a look at the test program:
> >
> >
> >
> > #0: "r1 = 8;"
> >
> > #1: "store_release((u64 *)(r10 - 8), r1);"
> >
> > #2: "r1 = *(u64 *)(r10 - 8);"
> >
> > #3: "r2 = r10;"
> >
> > #4: "r2 += r1;" /* mark_precise */
> >
> > #5: "r0 = 0;"
> >
> > #6: "exit;"
> >
> >
> >
> > At #1, if the verifier doesn't remember that we wrote 8 to the stack,
> >
> > then later at #4 we would be adding an unbounded scalar value to the
> >
> > stack pointer, which would cause the program to be rejected:
> >
> >
> >
> > VERIFIER LOG:
> >
> > =============
> >
> > ...
> >
> > math between fp pointer and register with unbounded min value is not allowed
> >
> >
> >
> > All new tests depend on the pre-defined __BPF_FEATURE_LOAD_ACQ_STORE_REL
> >
> > feature macro, which implies -mcpu>=v4.
> >
>
> This restriction would mean that tests are skipped on BPF CI, as it
>
> currently runs using llvm 17 and 18. Instead, I suggest using some
Eduard, if this feature requires a particular version of LLVM, it's
not difficult to add a configuration for it to BPF CI.
Whether we want to do it is an open question though. Issues may come
up with other tests when newer LLVM is used.
>
> macro hiding an inline assembly as below:
>
> asm volatile (".8byte %[insn];"
>
> :
>
> : [insn]"i"(*(long *)&(BPF_RAW_INSN(...)))
>
> : /* correct clobbers here */);
>
> See the usage of the __imm_insn() macro in the test suite.
>
> Also, "BPF_ATOMIC loads from R%d %s is not allowed\n" and
>
> "BPF_ATOMIC stores into R%d %s is not allowed\n"
>
> situations are not tested.
>
> [...]
>
> >
>
> [...]
>
