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selftests/bpf: Add tests for rbtree API interaction in sleepable progs

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Confirm that the following sleepable prog states fail verification:
  * bpf_rcu_read_unlock before bpf_spin_unlock
     * RCU CS will last at least as long as spin_lock CS

Also confirm that correct usage passes verification, specifically:
  * Explicit use of bpf_rcu_read_{lock, unlock} in sleepable test prog
  * Implied RCU CS due to spin_lock CS

None of the selftest progs actually attach to bpf_testmod's
bpf_testmod_test_read.

Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com>
Link: https://lore.kernel.org/r/20230821193311.3290257-8-davemarchevsky@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Dave Marchevsky 2023-08-21 12:33:11 -07:00 committed by Alexei Starovoitov
parent 5861d1e8db
commit 312aa5bde8
2 changed files with 99 additions and 0 deletions
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71
tools/testing/selftests/bpf/progs/refcounted_kptr.c
View file

@ -8,6 +8,9 @@
#include "bpf_misc.h"
#include "bpf_experimental.h"
extern void bpf_rcu_read_lock(void) __ksym;
extern void bpf_rcu_read_unlock(void) __ksym;
struct node_data {
long key;
long list_data;
@ -497,4 +500,72 @@ long rbtree_wrong_owner_remove_fail_a2(void *ctx)
return 0;
}
SEC("?fentry.s/bpf_testmod_test_read")
__success
int BPF_PROG(rbtree_sleepable_rcu,
struct file *file, struct kobject *kobj,
struct bin_attribute *bin_attr, char *buf, loff_t off, size_t len)
{
struct bpf_rb_node *rb;
struct node_data *n, *m = NULL;
n = bpf_obj_new(typeof(*n));
if (!n)
return 0;
bpf_rcu_read_lock();
bpf_spin_lock(&lock);
bpf_rbtree_add(&root, &n->r, less);
rb = bpf_rbtree_first(&root);
if (!rb)
goto err_out;
rb = bpf_rbtree_remove(&root, rb);
if (!rb)
goto err_out;
m = container_of(rb, struct node_data, r);
err_out:
bpf_spin_unlock(&lock);
bpf_rcu_read_unlock();
if (m)
bpf_obj_drop(m);
return 0;
}
SEC("?fentry.s/bpf_testmod_test_read")
__success
int BPF_PROG(rbtree_sleepable_rcu_no_explicit_rcu_lock,
struct file *file, struct kobject *kobj,
struct bin_attribute *bin_attr, char *buf, loff_t off, size_t len)
{
struct bpf_rb_node *rb;
struct node_data *n, *m = NULL;
n = bpf_obj_new(typeof(*n));
if (!n)
return 0;
/* No explicit bpf_rcu_read_lock */
bpf_spin_lock(&lock);
bpf_rbtree_add(&root, &n->r, less);
rb = bpf_rbtree_first(&root);
if (!rb)
goto err_out;
rb = bpf_rbtree_remove(&root, rb);
if (!rb)
goto err_out;
m = container_of(rb, struct node_data, r);
err_out:
bpf_spin_unlock(&lock);
/* No explicit bpf_rcu_read_unlock */
if (m)
bpf_obj_drop(m);
return 0;
}
char _license[] SEC("license") = "GPL";

28
tools/testing/selftests/bpf/progs/refcounted_kptr_fail.c
View file

@ -13,6 +13,9 @@ struct node_acquire {
struct bpf_refcount refcount;
};
extern void bpf_rcu_read_lock(void) __ksym;
extern void bpf_rcu_read_unlock(void) __ksym;
#define private(name) SEC(".data." #name) __hidden __attribute__((aligned(8)))
private(A) struct bpf_spin_lock glock;
private(A) struct bpf_rb_root groot __contains(node_acquire, node);
@ -71,4 +74,29 @@ long rbtree_refcounted_node_ref_escapes_owning_input(void *ctx)
return 0;
}
SEC("?fentry.s/bpf_testmod_test_read")
__failure __msg("function calls are not allowed while holding a lock")
int BPF_PROG(rbtree_fail_sleepable_lock_across_rcu,
struct file *file, struct kobject *kobj,
struct bin_attribute *bin_attr, char *buf, loff_t off, size_t len)
{
struct node_acquire *n;
n = bpf_obj_new(typeof(*n));
if (!n)
return 0;
/* spin_{lock,unlock} are in different RCU CS */
bpf_rcu_read_lock();
bpf_spin_lock(&glock);
bpf_rbtree_add(&groot, &n->node, less);
bpf_rcu_read_unlock();
bpf_rcu_read_lock();
bpf_spin_unlock(&glock);
bpf_rcu_read_unlock();
return 0;
}
char _license[] SEC("license") = "GPL";