From: Alexei Starovoitov ast@kernel.org
[ Upstream commit 62d101d5f422cde39b269f7eb4cbbe2f1e26f9d4 ]
The compiler is optimizing out majority of unref_ptr read/writes, so the test wasn't testing much. For example, one could delete '__kptr' tag from 'struct prog_test_ref_kfunc __kptr *unref_ptr;' and the test would still "pass".
Convert it to volatile stores. Confirmed by comparing bpf asm before/after.
Fixes: 2cbc469a6fc3 ("selftests/bpf: Add C tests for kptr") Signed-off-by: Alexei Starovoitov ast@kernel.org Acked-by: Stanislav Fomichev sdf@google.com Acked-by: Kumar Kartikeya Dwivedi memxor@gmail.com Link: https://lore.kernel.org/r/20230214235051.22938-1-alexei.starovoitov@gmail.co... Signed-off-by: Martin KaFai Lau martin.lau@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- tools/testing/selftests/bpf/progs/map_kptr.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-)
diff --git a/tools/testing/selftests/bpf/progs/map_kptr.c b/tools/testing/selftests/bpf/progs/map_kptr.c index eb82178034934..228ec45365a8d 100644 --- a/tools/testing/selftests/bpf/progs/map_kptr.c +++ b/tools/testing/selftests/bpf/progs/map_kptr.c @@ -62,21 +62,23 @@ extern struct prog_test_ref_kfunc * bpf_kfunc_call_test_kptr_get(struct prog_test_ref_kfunc **p, int a, int b) __ksym; extern void bpf_kfunc_call_test_release(struct prog_test_ref_kfunc *p) __ksym;
+#define WRITE_ONCE(x, val) ((*(volatile typeof(x) *) &(x)) = (val)) + static void test_kptr_unref(struct map_value *v) { struct prog_test_ref_kfunc *p;
p = v->unref_ptr; /* store untrusted_ptr_or_null_ */ - v->unref_ptr = p; + WRITE_ONCE(v->unref_ptr, p); if (!p) return; if (p->a + p->b > 100) return; /* store untrusted_ptr_ */ - v->unref_ptr = p; + WRITE_ONCE(v->unref_ptr, p); /* store NULL */ - v->unref_ptr = NULL; + WRITE_ONCE(v->unref_ptr, NULL); }
static void test_kptr_ref(struct map_value *v) @@ -85,7 +87,7 @@ static void test_kptr_ref(struct map_value *v)
p = v->ref_ptr; /* store ptr_or_null_ */ - v->unref_ptr = p; + WRITE_ONCE(v->unref_ptr, p); if (!p) return; if (p->a + p->b > 100) @@ -99,7 +101,7 @@ static void test_kptr_ref(struct map_value *v) return; } /* store ptr_ */ - v->unref_ptr = p; + WRITE_ONCE(v->unref_ptr, p); bpf_kfunc_call_test_release(p);
p = bpf_kfunc_call_test_acquire(&(unsigned long){0});