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Message-Id: <20230411041633.179404-2-void@manifault.com>
Date: Mon, 10 Apr 2023 23:16:32 -0500
From: David Vernet <void@...ifault.com>
To: bpf@...r.kernel.org
Cc: ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
martin.lau@...ux.dev, song@...nel.org, yhs@...com,
john.fastabend@...il.com, kpsingh@...nel.org, sdf@...gle.com,
haoluo@...gle.com, jolsa@...nel.org, linux-kernel@...r.kernel.org,
kernel-team@...a.com
Subject: [PATCH bpf-next 2/3] bpf: Remove bpf_cgroup_kptr_get() kfunc
Now that bpf_cgroup_acquire() is KF_RCU | KF_RET_NULL,
bpf_cgroup_kptr_get() is redundant. Let's remove it, and update
selftests to instead use bpf_cgroup_acquire() where appropriate. The
next patch will update the BPF documentation to not mention
bpf_cgroup_kptr_get().
Signed-off-by: David Vernet <void@...ifault.com>
---
kernel/bpf/helpers.c | 32 ---------
.../selftests/bpf/progs/cgrp_kfunc_common.h | 3 +-
.../selftests/bpf/progs/cgrp_kfunc_failure.c | 68 +++----------------
.../selftests/bpf/progs/cgrp_kfunc_success.c | 10 ++-
4 files changed, 14 insertions(+), 99 deletions(-)
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 71f0604bdc97..f04e60a4847f 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -2040,37 +2040,6 @@ __bpf_kfunc struct cgroup *bpf_cgroup_acquire(struct cgroup *cgrp)
return cgroup_tryget(cgrp) ? cgrp : NULL;
}
-/**
- * bpf_cgroup_kptr_get - Acquire a reference on a struct cgroup kptr. A cgroup
- * kptr acquired by this kfunc which is not subsequently stored in a map, must
- * be released by calling bpf_cgroup_release().
- * @cgrpp: A pointer to a cgroup kptr on which a reference is being acquired.
- */
-__bpf_kfunc struct cgroup *bpf_cgroup_kptr_get(struct cgroup **cgrpp)
-{
- struct cgroup *cgrp;
-
- rcu_read_lock();
- /* Another context could remove the cgroup from the map and release it
- * at any time, including after we've done the lookup above. This is
- * safe because we're in an RCU read region, so the cgroup is
- * guaranteed to remain valid until at least the rcu_read_unlock()
- * below.
- */
- cgrp = READ_ONCE(*cgrpp);
-
- if (cgrp && !cgroup_tryget(cgrp))
- /* If the cgroup had been removed from the map and freed as
- * described above, cgroup_tryget() will return false. The
- * cgroup will be freed at some point after the current RCU gp
- * has ended, so just return NULL to the user.
- */
- cgrp = NULL;
- rcu_read_unlock();
-
- return cgrp;
-}
-
/**
* bpf_cgroup_release - Release the reference acquired on a cgroup.
* If this kfunc is invoked in an RCU read region, the cgroup is guaranteed to
@@ -2314,7 +2283,6 @@ BTF_ID_FLAGS(func, bpf_rbtree_first, KF_RET_NULL)
#ifdef CONFIG_CGROUPS
BTF_ID_FLAGS(func, bpf_cgroup_acquire, KF_ACQUIRE | KF_RCU | KF_RET_NULL)
-BTF_ID_FLAGS(func, bpf_cgroup_kptr_get, KF_ACQUIRE | KF_KPTR_GET | KF_RET_NULL)
BTF_ID_FLAGS(func, bpf_cgroup_release, KF_RELEASE)
BTF_ID_FLAGS(func, bpf_cgroup_ancestor, KF_ACQUIRE | KF_RCU | KF_RET_NULL)
BTF_ID_FLAGS(func, bpf_cgroup_from_id, KF_ACQUIRE | KF_RET_NULL)
diff --git a/tools/testing/selftests/bpf/progs/cgrp_kfunc_common.h b/tools/testing/selftests/bpf/progs/cgrp_kfunc_common.h
index b0e279f4652b..22914a70db54 100644
--- a/tools/testing/selftests/bpf/progs/cgrp_kfunc_common.h
+++ b/tools/testing/selftests/bpf/progs/cgrp_kfunc_common.h
@@ -21,10 +21,11 @@ struct hash_map {
} __cgrps_kfunc_map SEC(".maps");
struct cgroup *bpf_cgroup_acquire(struct cgroup *p) __ksym;
-struct cgroup *bpf_cgroup_kptr_get(struct cgroup **pp) __ksym;
void bpf_cgroup_release(struct cgroup *p) __ksym;
struct cgroup *bpf_cgroup_ancestor(struct cgroup *cgrp, int level) __ksym;
struct cgroup *bpf_cgroup_from_id(u64 cgid) __ksym;
+void bpf_rcu_read_lock(void) __ksym;
+void bpf_rcu_read_unlock(void) __ksym;
static inline struct __cgrps_kfunc_map_value *cgrps_kfunc_map_value_lookup(struct cgroup *cgrp)
{
diff --git a/tools/testing/selftests/bpf/progs/cgrp_kfunc_failure.c b/tools/testing/selftests/bpf/progs/cgrp_kfunc_failure.c
index 49347f12de39..0fa564a5cc5b 100644
--- a/tools/testing/selftests/bpf/progs/cgrp_kfunc_failure.c
+++ b/tools/testing/selftests/bpf/progs/cgrp_kfunc_failure.c
@@ -133,59 +133,6 @@ int BPF_PROG(cgrp_kfunc_acquire_unreleased, struct cgroup *cgrp, const char *pat
return 0;
}
-SEC("tp_btf/cgroup_mkdir")
-__failure __msg("arg#0 expected pointer to map value")
-int BPF_PROG(cgrp_kfunc_get_non_kptr_param, struct cgroup *cgrp, const char *path)
-{
- struct cgroup *kptr;
-
- /* Cannot use bpf_cgroup_kptr_get() on a non-kptr, even on a valid cgroup. */
- kptr = bpf_cgroup_kptr_get(&cgrp);
- if (!kptr)
- return 0;
-
- bpf_cgroup_release(kptr);
-
- return 0;
-}
-
-SEC("tp_btf/cgroup_mkdir")
-__failure __msg("arg#0 expected pointer to map value")
-int BPF_PROG(cgrp_kfunc_get_non_kptr_acquired, struct cgroup *cgrp, const char *path)
-{
- struct cgroup *kptr, *acquired;
-
- acquired = bpf_cgroup_acquire(cgrp);
- if (!acquired)
- return 0;
-
- /* Cannot use bpf_cgroup_kptr_get() on a non-map-value, even if the kptr was acquired. */
- kptr = bpf_cgroup_kptr_get(&acquired);
- bpf_cgroup_release(acquired);
- if (!kptr)
- return 0;
-
- bpf_cgroup_release(kptr);
-
- return 0;
-}
-
-SEC("tp_btf/cgroup_mkdir")
-__failure __msg("arg#0 expected pointer to map value")
-int BPF_PROG(cgrp_kfunc_get_null, struct cgroup *cgrp, const char *path)
-{
- struct cgroup *kptr;
-
- /* Cannot use bpf_cgroup_kptr_get() on a NULL pointer. */
- kptr = bpf_cgroup_kptr_get(NULL);
- if (!kptr)
- return 0;
-
- bpf_cgroup_release(kptr);
-
- return 0;
-}
-
SEC("tp_btf/cgroup_mkdir")
__failure __msg("Unreleased reference")
int BPF_PROG(cgrp_kfunc_xchg_unreleased, struct cgroup *cgrp, const char *path)
@@ -207,8 +154,8 @@ int BPF_PROG(cgrp_kfunc_xchg_unreleased, struct cgroup *cgrp, const char *path)
}
SEC("tp_btf/cgroup_mkdir")
-__failure __msg("Unreleased reference")
-int BPF_PROG(cgrp_kfunc_get_unreleased, struct cgroup *cgrp, const char *path)
+__failure __msg("must be referenced or trusted")
+int BPF_PROG(cgrp_kfunc_rcu_get_release, struct cgroup *cgrp, const char *path)
{
struct cgroup *kptr;
struct __cgrps_kfunc_map_value *v;
@@ -217,11 +164,12 @@ int BPF_PROG(cgrp_kfunc_get_unreleased, struct cgroup *cgrp, const char *path)
if (!v)
return 0;
- kptr = bpf_cgroup_kptr_get(&v->cgrp);
- if (!kptr)
- return 0;
-
- /* Kptr acquired above is never released. */
+ bpf_rcu_read_lock();
+ kptr = v->cgrp;
+ if (kptr)
+ /* Can't release a cgroup kptr stored in a map. */
+ bpf_cgroup_release(kptr);
+ bpf_rcu_read_unlock();
return 0;
}
diff --git a/tools/testing/selftests/bpf/progs/cgrp_kfunc_success.c b/tools/testing/selftests/bpf/progs/cgrp_kfunc_success.c
index e9dbd1af05a7..5354455a01be 100644
--- a/tools/testing/selftests/bpf/progs/cgrp_kfunc_success.c
+++ b/tools/testing/selftests/bpf/progs/cgrp_kfunc_success.c
@@ -126,13 +126,11 @@ int BPF_PROG(test_cgrp_get_release, struct cgroup *cgrp, const char *path)
return 0;
}
- kptr = bpf_cgroup_kptr_get(&v->cgrp);
- if (!kptr) {
+ bpf_rcu_read_lock();
+ kptr = v->cgrp;
+ if (!kptr)
err = 3;
- return 0;
- }
-
- bpf_cgroup_release(kptr);
+ bpf_rcu_read_unlock();
return 0;
}
--
2.40.0
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