[PATCH bpf-next v1 2/2] selftests/bpf: test refining u32/s32 bounds when ranges cross min/max boundary

[Eduard Zingerman <eddyz87@gmail.com>]

Two test cases for signed/unsigned 32-bit bounds refinement
when s32 range crosses the sign boundary:
- s32 range [S32_MIN..1] overlapping with u32 range [3..U32_MAX],
  s32 range tail before sign boundary overlaps with u32 range.
- s32 range [-3..5] overlapping with u32 range [0..S32_MIN+3],
  s32 range head after the sign boundary overlaps with u32 range.

This covers both branches added in the __reg32_deduce_bounds().

Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
---
 .../selftests/bpf/progs/verifier_bounds.c     | 37 +++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/tools/testing/selftests/bpf/progs/verifier_bounds.c b/tools/testing/selftests/bpf/progs/verifier_bounds.c
index 4588e5b55b41..0c2a62b16ec4 100644
--- a/tools/testing/selftests/bpf/progs/verifier_bounds.c
+++ b/tools/testing/selftests/bpf/progs/verifier_bounds.c
@@ -2000,4 +2000,41 @@ __naked void bounds_refinement_multiple_overlaps(void *ctx)
 	: __clobber_all);
 }
 
+SEC("socket")
+__success
+__flag(BPF_F_TEST_REG_INVARIANTS)
+__naked void signed_unsigned_intersection32_case1(void *ctx)
+{
+	asm volatile("									\
+	call %[bpf_get_prandom_u32];							\
+	w0 &= 0xffffffff;								\
+	if w0 < 0x3 goto 1f;		/* on fall-through u32 range [3..U32_MAX]  */	\
+	if w0 s> 0x1 goto 1f;		/* on fall-through s32 range [S32_MIN..1]  */	\
+	if w0 s< 0x0 goto 1f;		/* range can be narrowed to  [S32_MIN..-1] */	\
+	r10 = 0;			/* thus predicting the jump. */			\
+1:	exit;										\
+"	:
+	: __imm(bpf_get_prandom_u32)
+	: __clobber_all);
+}
+
+SEC("socket")
+__success
+__flag(BPF_F_TEST_REG_INVARIANTS)
+__naked void signed_unsigned_intersection32_case2(void *ctx)
+{
+	asm volatile("									\
+	call %[bpf_get_prandom_u32];							\
+	w0 &= 0xffffffff;								\
+	if w0 > 0x80000003 goto 1f;	/* on fall-through u32 range [0..S32_MIN+3] */	\
+	if w0 s< -3 goto 1f;		/* on fall-through s32 range [-3..S32_MAX] */	\
+	if w0 s> 5 goto 1f;		/* on fall-through s32 range [-3..5] */		\
+	if w0 <= 5 goto 1f;		/* range can be narrowed to  [0..5] */		\
+	r10 = 0;			/* thus predicting the jump */			\
+1:	exit;										\
+"	:
+	: __imm(bpf_get_prandom_u32)
+	: __clobber_all);
+}
+
 char _license[] SEC("license") = "GPL";
-- 
2.51.1