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selftests/bpf: Add a selftest with not-8-byte aligned BPF_ST

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Add a selftest with a 4 bytes BPF_ST of 0 where the store is not
8-byte aligned. The goal is to ensure that STACK_ZERO is properly
marked in stack slots and the STACK_ZERO value can propagate
properly during the load.

Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20240110051355.2737232-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Yonghong Song
2024-01-09 21:13:55 -08:00
committed by Alexei Starovoitov
parent 9a4c57f52b
commit 6ae99ac8b7
1 changed files with 41 additions and 0 deletions
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41
tools/testing/selftests/bpf/progs/verifier_spill_fill.c
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@@ -581,6 +581,47 @@ __naked void partial_stack_load_preserves_zeros(void)
: __clobber_common);
}
SEC("raw_tp")
__log_level(2)
__success
/* fp-4 is STACK_ZERO */
__msg("2: (62) *(u32 *)(r10 -4) = 0 ; R10=fp0 fp-8=0000????")
__msg("4: (71) r2 = *(u8 *)(r10 -1) ; R2_w=0 R10=fp0 fp-8=0000????")
__msg("5: (0f) r1 += r2")
__msg("mark_precise: frame0: last_idx 5 first_idx 0 subseq_idx -1")
__msg("mark_precise: frame0: regs=r2 stack= before 4: (71) r2 = *(u8 *)(r10 -1)")
__naked void partial_stack_load_preserves_partial_zeros(void)
{
asm volatile (
/* fp-4 is value zero */
".8byte %[fp4_st_zero];" /* LLVM-18+: *(u32 *)(r10 -4) = 0; */
/* load single U8 from non-aligned stack zero slot */
"r1 = %[single_byte_buf];"
"r2 = *(u8 *)(r10 -1);"
"r1 += r2;"
"*(u8 *)(r1 + 0) = r2;" /* this should be fine */
/* load single U16 from non-aligned stack zero slot */
"r1 = %[single_byte_buf];"
"r2 = *(u16 *)(r10 -2);"
"r1 += r2;"
"*(u8 *)(r1 + 0) = r2;" /* this should be fine */
/* load single U32 from non-aligned stack zero slot */
"r1 = %[single_byte_buf];"
"r2 = *(u32 *)(r10 -4);"
"r1 += r2;"
"*(u8 *)(r1 + 0) = r2;" /* this should be fine */
"r0 = 0;"
"exit;"
:
: __imm_ptr(single_byte_buf),
__imm_insn(fp4_st_zero, BPF_ST_MEM(BPF_W, BPF_REG_FP, -4, 0))
: __clobber_common);
}
char two_byte_buf[2] SEC(".data.two_byte_buf");
SEC("raw_tp")