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selftests/bpf: add testcase to verifier_bounds.c for BPF_JNE

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Add testcase for the logic that the verifier tracks the BPF_JNE for regs.
The assembly function "reg_not_equal_const()" and "reg_equal_const" that
we add is exactly converted from the following case:

  u32 a = bpf_get_prandom_u32();
  u64 b = 0;

  a %= 8;
  /* the "a > 0" here will be optimized to "a != 0" */
  if (a > 0) {
    /* now the range of a should be [1, 7] */
    bpf_skb_store_bytes(skb, 0, &b, a, 0);
  }

Signed-off-by: Menglong Dong <menglong8.dong@gmail.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20231219134800.1550388-5-menglong8.dong@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Menglong Dong
2023-12-19 21:48:00 +08:00
committed by Alexei Starovoitov
parent 31d9cc96b1
commit 463ea64eb0
1 changed files with 62 additions and 0 deletions
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62
tools/testing/selftests/bpf/progs/verifier_bounds.c
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@@ -1075,4 +1075,66 @@ l0_%=: r0 = 0; \
: __clobber_all);
}
SEC("tc")
__description("bounds check with JMP_NE for reg edge")
__success __retval(0)
__naked void reg_not_equal_const(void)
{
asm volatile (" \
r6 = r1; \
r1 = 0; \
*(u64*)(r10 - 8) = r1; \
call %[bpf_get_prandom_u32]; \
r4 = r0; \
r4 &= 7; \
if r4 != 0 goto l0_%=; \
r0 = 0; \
exit; \
l0_%=: r1 = r6; \
r2 = 0; \
r3 = r10; \
r3 += -8; \
r5 = 0; \
/* The 4th argument of bpf_skb_store_bytes is defined as \
* ARG_CONST_SIZE, so 0 is not allowed. The 'r4 != 0' \
* is providing us this exclusion of zero from initial \
* [0, 7] range. \
*/ \
call %[bpf_skb_store_bytes]; \
r0 = 0; \
exit; \
" :
: __imm(bpf_get_prandom_u32),
__imm(bpf_skb_store_bytes)
: __clobber_all);
}
SEC("tc")
__description("bounds check with JMP_EQ for reg edge")
__success __retval(0)
__naked void reg_equal_const(void)
{
asm volatile (" \
r6 = r1; \
r1 = 0; \
*(u64*)(r10 - 8) = r1; \
call %[bpf_get_prandom_u32]; \
r4 = r0; \
r4 &= 7; \
if r4 == 0 goto l0_%=; \
r1 = r6; \
r2 = 0; \
r3 = r10; \
r3 += -8; \
r5 = 0; \
/* Just the same as what we do in reg_not_equal_const() */ \
call %[bpf_skb_store_bytes]; \
l0_%=: r0 = 0; \
exit; \
" :
: __imm(bpf_get_prandom_u32),
__imm(bpf_skb_store_bytes)
: __clobber_all);
}
char _license[] SEC("license") = "GPL";