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selftests/bpf: Fix map_kptr test.

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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: 2cbc469a6f ("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.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
This commit is contained in:
Alexei Starovoitov 2023-02-14 15:50:51 -08:00 • committed by Martin KaFai Lau
parent 5e53e5c7ed
commit 62d101d5f4
1 changed files with 7 additions and 5 deletions
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12
tools/testing/selftests/bpf/progs/map_kptr.c
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@ -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});