selftests/bpf: check if imprecise stack spills confuse infinite loop detection

Verify that infinite loop detection logic separates states with
identical register states but different imprecise scalars spilled to
stack.

Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20240108205209.838365-4-maxtram95@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/tools/testing/selftests/bpf/progs/verifier_loops1.c b/tools/testing/selftests/bpf/progs/verifier_loops1.c
index 71735dbf33d4f868e32197fe5e6e051da9fa87da..e07b43b78fd21071f3386ab8d3a481f534c99749 100644 (file)
--- a/tools/testing/selftests/bpf/progs/verifier_loops1.c
+++ b/tools/testing/selftests/bpf/progs/verifier_loops1.c
@@ -259,4 +259,28 @@ l0_%=:     r2 += r1;                                       \
 "      ::: __clobber_all);
 }
 
+SEC("xdp")
+__success
+__naked void not_an_inifinite_loop(void)
+{
+       asm volatile ("                                 \
+       call %[bpf_get_prandom_u32];                    \
+       r0 &= 0xff;                                     \
+       *(u64 *)(r10 - 8) = r0;                         \
+       r0 = 0;                                         \
+loop_%=:                                               \
+       r0 = *(u64 *)(r10 - 8);                         \
+       if r0 > 10 goto exit_%=;                        \
+       r0 += 1;                                        \
+       *(u64 *)(r10 - 8) = r0;                         \
+       r0 = 0;                                         \
+       goto loop_%=;                                   \
+exit_%=:                                               \
+       r0 = 0;                                         \
+       exit;                                           \
+"      :
+       : __imm(bpf_get_prandom_u32)
+       : __clobber_all);
+}
+
 char _license[] SEC("license") = "GPL";