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selftests/bpf: validate precision logic in partial_stack_load_preserves_zeros

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Enhance partial_stack_load_preserves_zeros subtest with detailed
precision propagation log checks. We know expect fp-16 to be spilled,
initially imprecise, zero const register, which is later marked as
precise even when partial stack slot load is performed, even if it's not
a register fill (!).

Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20231205184248.1502704-10-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Andrii Nakryiko 2023-12-05 10:42:47 -08:00 committed by Alexei Starovoitov
parent 18a433b620
commit 064e0bea19
1 changed files with 16 additions and 0 deletions
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16
tools/testing/selftests/bpf/progs/verifier_spill_fill.c
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@ -495,6 +495,22 @@ char single_byte_buf[1] SEC(".data.single_byte_buf");
SEC("raw_tp")
__log_level(2)
__success
/* make sure fp-8 is all STACK_ZERO */
__msg("2: (7a) *(u64 *)(r10 -8) = 0 ; R10=fp0 fp-8_w=00000000")
/* but fp-16 is spilled IMPRECISE zero const reg */
__msg("4: (7b) *(u64 *)(r10 -16) = r0 ; R0_w=0 R10=fp0 fp-16_w=0")
/* and now check that precision propagation works even for such tricky case */
__msg("10: (71) r2 = *(u8 *)(r10 -9) ; R2_w=P0 R10=fp0 fp-16_w=0")
__msg("11: (0f) r1 += r2")
__msg("mark_precise: frame0: last_idx 11 first_idx 0 subseq_idx -1")
__msg("mark_precise: frame0: regs=r2 stack= before 10: (71) r2 = *(u8 *)(r10 -9)")
__msg("mark_precise: frame0: regs= stack=-16 before 9: (bf) r1 = r6")
__msg("mark_precise: frame0: regs= stack=-16 before 8: (73) *(u8 *)(r1 +0) = r2")
__msg("mark_precise: frame0: regs= stack=-16 before 7: (0f) r1 += r2")
__msg("mark_precise: frame0: regs= stack=-16 before 6: (71) r2 = *(u8 *)(r10 -1)")
__msg("mark_precise: frame0: regs= stack=-16 before 5: (bf) r1 = r6")
__msg("mark_precise: frame0: regs= stack=-16 before 4: (7b) *(u64 *)(r10 -16) = r0")
__msg("mark_precise: frame0: regs=r0 stack= before 3: (b7) r0 = 0")
__naked void partial_stack_load_preserves_zeros(void)
{
asm volatile (