Commit 62d101d5 authored by Alexei Starovoitov's avatar Alexei Starovoitov Committed by Martin KaFai Lau
Browse files

selftests/bpf: Fix map_kptr test. 



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: 2cbc469a ("selftests/bpf: Add C tests for kptr")
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarStanislav Fomichev <sdf@google.com>
Acked-by: default avatarKumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20230214235051.22938-1-alexei.starovoitov@gmail.com


Signed-off-by: default avatarMartin KaFai Lau <martin.lau@kernel.org>
parent 5e53e5c7

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

+7 −5
Original line number Diff line number Diff line
@@ -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});