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selftests/bpf: Add test for bpf_ksym_exists().

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Add load and run time test for bpf_ksym_exists() and check that the verifier
performs dead code elimination for non-existing kfunc.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Reviewed-by: Martin KaFai Lau <martin.lau@kernel.org>
Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20230317201920.62030-5-alexei.starovoitov@gmail.com
This commit is contained in:
Alexei Starovoitov 2023-03-17 13:19:20 -07:00 committed by Andrii Nakryiko
parent 5cbd3fe3a9
commit 95fdf6e313
1 changed files with 19 additions and 1 deletions
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20
tools/testing/selftests/bpf/progs/task_kfunc_success.c
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@ -17,6 +17,10 @@ int err, pid;
* TP_PROTO(struct task_struct *p, u64 clone_flags)
*/
struct task_struct *bpf_task_acquire(struct task_struct *p) __ksym __weak;
void invalid_kfunc(void) __ksym __weak;
void bpf_testmod_test_mod_kfunc(int i) __ksym __weak;
static bool is_test_kfunc_task(void)
{
int cur_pid = bpf_get_current_pid_tgid() >> 32;
@ -26,7 +30,21 @@ static bool is_test_kfunc_task(void)
static int test_acquire_release(struct task_struct *task)
{
struct task_struct *acquired;
struct task_struct *acquired = NULL;
if (!bpf_ksym_exists(bpf_task_acquire)) {
err = 3;
return 0;
}
if (!bpf_ksym_exists(bpf_testmod_test_mod_kfunc)) {
err = 4;
return 0;
}
if (bpf_ksym_exists(invalid_kfunc)) {
/* the verifier's dead code elimination should remove this */
err = 5;
asm volatile ("goto -1"); /* for (;;); */
}
acquired = bpf_task_acquire(task);
bpf_task_release(acquired);