This instruction has an interesting behavior for negative values of immediate, to be thorough I would test them as well. Fixed x86 should pass but who knows.
I would also welcome a test reproducing the problem with shifts. For the narrow scope of this test, Acked-by: Marat Khalili <[email protected]> > -----Original Message----- > From: Stephen Hemminger <[email protected]> > Sent: Sunday 21 June 2026 17:24 > To: [email protected] > Cc: Stephen Hemminger <[email protected]>; Konstantin Ananyev > <[email protected]>; > Marat Khalili <[email protected]> > Subject: [PATCH v3 2/6] test/bpf: add JSET test with small immediate > > The existing jump test only used a 32-bit JSET mask, > so the broken imm8 encoding of TEST in the x86 JIT was never exercised. > Add a case with a byte-sized mask; > run_test() runs it through the interpreter and the JIT. > > Signed-off-by: Stephen Hemminger <[email protected]> > --- > app/test/test_bpf.c | 82 +++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 82 insertions(+) > > diff --git a/app/test/test_bpf.c b/app/test/test_bpf.c > index dd24722450..e70dea736f 100644 > --- a/app/test/test_bpf.c > +++ b/app/test/test_bpf.c > @@ -3158,7 +3158,89 @@ static const struct ebpf_insn test_ld_mbuf3_prog[] = { > }; > > /* all bpf test cases */ > +/* > + * JSET with a byte-sized mask: exercises the imm8 path of the TEST > + * encoding in the x86 JIT (a 32-bit mask takes a different path). > + */ > +static const struct ebpf_insn test_jset1_prog[] = { > + { > + .code = (BPF_ALU | EBPF_MOV | BPF_K), > + .dst_reg = EBPF_REG_0, > + .imm = 0, > + }, > + { > + .code = (BPF_LDX | BPF_MEM | BPF_B), > + .dst_reg = EBPF_REG_2, > + .src_reg = EBPF_REG_1, > + .off = offsetof(struct dummy_offset, u8), > + }, > + /* bit 0 is set in the input: branch is taken */ > + { > + .code = (BPF_JMP | BPF_JSET | BPF_K), > + .dst_reg = EBPF_REG_2, > + .imm = 0x1, > + .off = 1, > + }, > + { > + .code = (BPF_JMP | BPF_JA), > + .off = 1, > + }, > + { > + .code = (EBPF_ALU64 | BPF_OR | BPF_K), > + .dst_reg = EBPF_REG_0, > + .imm = 0x1, > + }, > + /* bit 1 is clear in the input: branch is not taken */ > + { > + .code = (BPF_JMP | BPF_JSET | BPF_K), > + .dst_reg = EBPF_REG_2, > + .imm = 0x2, > + .off = 1, > + }, > + { > + .code = (BPF_JMP | BPF_JA), > + .off = 1, > + }, > + { > + .code = (EBPF_ALU64 | BPF_OR | BPF_K), > + .dst_reg = EBPF_REG_0, > + .imm = 0x2, > + }, > + { > + .code = (BPF_JMP | EBPF_EXIT), > + }, > +}; > + > +static void > +test_jset1_prepare(void *arg) > +{ > + struct dummy_offset *df = arg; > + > + memset(df, 0, sizeof(*df)); > + df->u8 = 0x1; /* bit 0 set, bit 1 clear */ > +} > + > +static int > +test_jset1_check(uint64_t rc, const void *arg) > +{ > + return cmp_res(__func__, 0x1, rc, arg, arg, 0); > +} > + > static const struct bpf_test tests[] = { > + { > + .name = "test_jset1", > + .arg_sz = sizeof(struct dummy_offset), > + .prm = { > + .ins = test_jset1_prog, > + .nb_ins = RTE_DIM(test_jset1_prog), > + .prog_arg = { > + .type = RTE_BPF_ARG_PTR, > + .size = sizeof(struct dummy_offset), > + }, > + }, > + .prepare = test_jset1_prepare, > + .check_result = test_jset1_check, > + }, > { > .name = "test_store1", > .arg_sz = sizeof(struct dummy_offset), > -- > 2.53.0
