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selftests/bpf: validate zero preservation for sub-slot loads

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Validate that 1-, 2-, and 4-byte loads from stack slots not aligned on
8-byte boundary still preserve zero, when loading from all-STACK_ZERO
sub-slots, or when stack sub-slots are covered by spilled register with
known constant zero value.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20231205184248.1502704-8-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Andrii Nakryiko 2023-12-05 10:42:45 -08:00 committed by Alexei Starovoitov
parent e322f0bcb8
commit add1cd7f22
1 changed files with 71 additions and 0 deletions
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71
tools/testing/selftests/bpf/progs/verifier_spill_fill.c
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@ -490,4 +490,75 @@ __naked void spill_subregs_preserve_stack_zero(void)
: __clobber_all);
}
char single_byte_buf[1] SEC(".data.single_byte_buf");
SEC("raw_tp")
__log_level(2)
__success
__naked void partial_stack_load_preserves_zeros(void)
{
asm volatile (
/* fp-8 is all STACK_ZERO */
".8byte %[fp8_st_zero];" /* LLVM-18+: *(u64 *)(r10 -8) = 0; */
/* fp-16 is const zero register */
"r0 = 0;"
"*(u64 *)(r10 -16) = r0;"
/* 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 U8 from non-aligned ZERO REG slot */
"r1 = %[single_byte_buf];"
"r2 = *(u8 *)(r10 -9);"
"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 U16 from non-aligned ZERO REG slot */
"r1 = %[single_byte_buf];"
"r2 = *(u16 *)(r10 -10);"
"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 */
/* load single U32 from non-aligned ZERO REG slot */
"r1 = %[single_byte_buf];"
"r2 = *(u32 *)(r10 -12);"
"r1 += r2;"
"*(u8 *)(r1 + 0) = r2;" /* this should be fine */
/* for completeness, load U64 from STACK_ZERO slot */
"r1 = %[single_byte_buf];"
"r2 = *(u64 *)(r10 -8);"
"r1 += r2;"
"*(u8 *)(r1 + 0) = r2;" /* this should be fine */
/* for completeness, load U64 from ZERO REG slot */
"r1 = %[single_byte_buf];"
"r2 = *(u64 *)(r10 -16);"
"r1 += r2;"
"*(u8 *)(r1 + 0) = r2;" /* this should be fine */
"r0 = 0;"
"exit;"
:
: __imm_ptr(single_byte_buf),
__imm_insn(fp8_st_zero, BPF_ST_MEM(BPF_DW, BPF_REG_FP, -8, 0))
: __clobber_common);
}
char _license[] SEC("license") = "GPL";