selftests/bpf: Expand coverage of preempt tests to sleepable kfunc

JIRA: https://issues.redhat.com/browse/RHEL-78201

commit e8c6c80
Author: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Date:   Tue Dec 3 19:03:59 2024 -0800

    selftests/bpf: Expand coverage of preempt tests to sleepable kfunc

    For preemption-related kfuncs, we don't test their interaction with
    sleepable kfuncs (we do test helpers) even though the verifier has
    code to protect against such a pattern. Expand coverage of the selftest
    to include this case.

    Acked-by: Eduard Zingerman <eddyz87@gmail.com>
    Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
    Link: https://lore.kernel.org/r/20241204030400.208005-7-memxor@gmail.com
    Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Signed-off-by: Jerome Marchand <jmarchan@redhat.com>

Author: jeromemarchand

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

@@ -5,6 +5,8 @@
 #include "bpf_misc.h"
 #include "bpf_experimental.h"
 
+extern int bpf_copy_from_user_str(void *dst, u32 dst__sz, const void *unsafe_ptr__ign, u64 flags) __weak __ksym;
+
 SEC("?tc")
 __failure __msg("BPF_EXIT instruction in main prog cannot be used inside bpf_preempt_disable-ed region")
 int preempt_lock_missing_1(struct __sk_buff *ctx)
@@ -113,6 +115,18 @@ int preempt_sleepable_helper(void *ctx)
 	return 0;
 }
 
+SEC("?fentry.s/" SYS_PREFIX "sys_getpgid")
+__failure __msg("kernel func bpf_copy_from_user_str is sleepable within non-preemptible region")
+int preempt_sleepable_kfunc(void *ctx)
+{
+	u32 data;
+
+	bpf_preempt_disable();
+	bpf_copy_from_user_str(&data, sizeof(data), NULL, 0);
+	bpf_preempt_enable();
+	return 0;
+}
+
 int __noinline preempt_global_subprog(void)
 {
 	preempt_balance_subprog();