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selftests/bpf: adjust OP_EQ/OP_NE handling to use subranges for branch taken

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Similar to kernel-side BPF verifier logic enhancements, use 32-bit
subrange knowledge for is_branch_taken() logic in reg_bounds selftests.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20231112010609.848406-9-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Andrii Nakryiko 2023-11-11 17:06:04 -08:00 committed by Alexei Starovoitov
parent 8863238993
commit 774f94c5e7
1 changed files with 26 additions and 4 deletions
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30
tools/testing/selftests/bpf/prog_tests/reg_bounds.c
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@ -748,16 +748,38 @@ static int reg_state_branch_taken_op(enum num_t t, struct reg_state *x, struct r
/* OP_EQ and OP_NE are sign-agnostic */
enum num_t tu = t_unsigned(t);
enum num_t ts = t_signed(t);
int br_u, br_s;
int br_u, br_s, br;
br_u = range_branch_taken_op(tu, x->r[tu], y->r[tu], op);
br_s = range_branch_taken_op(ts, x->r[ts], y->r[ts], op);
if (br_u >= 0 && br_s >= 0 && br_u != br_s)
ASSERT_FALSE(true, "branch taken inconsistency!\n");
if (br_u >= 0)
return br_u;
return br_s;
/* if 64-bit ranges are indecisive, use 32-bit subranges to
* eliminate always/never taken branches, if possible
*/
if (br_u == -1 && (t == U64 || t == S64)) {
br = range_branch_taken_op(U32, x->r[U32], y->r[U32], op);
/* we can only reject for OP_EQ, never take branch
* based on lower 32 bits
*/
if (op == OP_EQ && br == 0)
return 0;
/* for OP_NEQ we can be conclusive only if lower 32 bits
* differ and thus inequality branch is always taken
*/
if (op == OP_NE && br == 1)
return 1;
br = range_branch_taken_op(S32, x->r[S32], y->r[S32], op);
if (op == OP_EQ && br == 0)
return 0;
if (op == OP_NE && br == 1)
return 1;
}
return br_u >= 0 ? br_u : br_s;
}
return range_branch_taken_op(t, x->r[t], y->r[t], op);
}