selftests/bpf: Add test for conditional jumps on same register

Add a test case to verify that conditional jumps on the same register
(e.g., JGT r0 > r0) do not trigger verifier BUG warnings when the register
holds a scalar with range.

Signed-off-by: KaFai Wan <[email protected]>

Author: mannkafai

tools/testing/selftests/bpf/progs/verifier_bounds.c

@@ -1709,4 +1709,21 @@ __naked void jeq_disagreeing_tnums(void *ctx)
 	: __clobber_all);
 }
 
+SEC("socket")
+__description("JGT on same register")
+__success __log_level(2)
+__naked void jgt_same_register(void *ctx)
+{
+	asm volatile("			\
+	call %[bpf_get_prandom_u32];	\
+	w8 = 0x80000000;		\
+	r0 &= r8;			\
+	if r0 > r0 goto +1;		\
+	call %[bpf_get_prandom_u32];	\
+	exit;				\
+"	:
+	: __imm(bpf_get_prandom_u32)
+	: __clobber_all);
+}
+
 char _license[] SEC("license") = "GPL";