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* [PATCH v6 bpf-next 0/6] bpf: enable task local storage for tracing programs
@ 2021-02-25 23:43 Song Liu
  2021-02-25 23:43 ` [PATCH v6 bpf-next 1/6] " Song Liu
                   ` (6 more replies)
  0 siblings, 7 replies; 10+ messages in thread
From: Song Liu @ 2021-02-25 23:43 UTC (permalink / raw)
  To: bpf, netdev, linux-kernel; +Cc: ast, daniel, kernel-team, peterz, Song Liu

This set enables task local storage for non-BPF_LSM programs.

It is common for tracing BPF program to access per-task data. Currently,
these data are stored in hash tables with pid as the key. In
bcc/libbpftools [1], 9 out of 23 tools use such hash tables. However,
hash table is not ideal for many use case. Task local storage provides
better usability and performance for BPF programs. Please refer to 6/6 for
some performance comparison of task local storage vs. hash table.

Changes v5 => v6:
1. Add inc/dec bpf_task_storage_busy in bpf_local_storage_map_free().

Changes v4 => v5:
1. Fix build w/o CONFIG_NET. (kernel test robot)
2. Remove unnecessary check for !task_storage_ptr(). (Martin)
3. Small changes in commit logs.

Changes v3 => v4:
1. Prevent deadlock from recursive calls of bpf_task_storage_[get|delete].
   (2/6 checks potential deadlock and fails over, 4/6 adds a selftest).

Changes v2 => v3:
1. Make the selftest more robust. (Andrii)
2. Small changes with runqslower. (Andrii)
3. Shortern CC list to make it easy for vger.

Changes v1 => v2:
1. Do not allocate task local storage when the task is being freed.
2. Revise the selftest and added a new test for a task being freed.
3. Minor changes in runqslower.

Song Liu (6):
  bpf: enable task local storage for tracing programs
  bpf: prevent deadlock from recursive bpf_task_storage_[get|delete]
  selftests/bpf: add non-BPF_LSM test for task local storage
  selftests/bpf: test deadlock from recursive
    bpf_task_storage_[get|delete]
  bpf: runqslower: prefer using local vmlimux to generate vmlinux.h
  bpf: runqslower: use task local storage

 include/linux/bpf.h                           |   7 ++
 include/linux/bpf_local_storage.h             |   3 +-
 include/linux/bpf_lsm.h                       |  22 ----
 include/linux/bpf_types.h                     |   2 +-
 include/linux/sched.h                         |   5 +
 kernel/bpf/Makefile                           |   3 +-
 kernel/bpf/bpf_inode_storage.c                |   2 +-
 kernel/bpf/bpf_local_storage.c                |  39 ++++---
 kernel/bpf/bpf_lsm.c                          |   4 -
 kernel/bpf/bpf_task_storage.c                 | 100 +++++++++++-------
 kernel/fork.c                                 |   5 +
 kernel/trace/bpf_trace.c                      |   4 +
 net/core/bpf_sk_storage.c                     |   2 +-
 tools/bpf/runqslower/Makefile                 |   5 +-
 tools/bpf/runqslower/runqslower.bpf.c         |  33 +++---
 .../bpf/prog_tests/task_local_storage.c       |  92 ++++++++++++++++
 .../selftests/bpf/progs/task_local_storage.c  |  64 +++++++++++
 .../bpf/progs/task_local_storage_exit_creds.c |  32 ++++++
 .../selftests/bpf/progs/task_ls_recursion.c   |  70 ++++++++++++
 19 files changed, 398 insertions(+), 96 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/task_local_storage.c
 create mode 100644 tools/testing/selftests/bpf/progs/task_local_storage.c
 create mode 100644 tools/testing/selftests/bpf/progs/task_local_storage_exit_creds.c
 create mode 100644 tools/testing/selftests/bpf/progs/task_ls_recursion.c

--
2.24.1

^ permalink raw reply	[flat|nested] 10+ messages in thread

* [PATCH v6 bpf-next 1/6] bpf: enable task local storage for tracing programs
  2021-02-25 23:43 [PATCH v6 bpf-next 0/6] bpf: enable task local storage for tracing programs Song Liu
@ 2021-02-25 23:43 ` Song Liu
  2021-02-25 23:43 ` [PATCH v6 bpf-next 2/6] bpf: prevent deadlock from recursive bpf_task_storage_[get|delete] Song Liu
                   ` (5 subsequent siblings)
  6 siblings, 0 replies; 10+ messages in thread
From: Song Liu @ 2021-02-25 23:43 UTC (permalink / raw)
  To: bpf, netdev, linux-kernel
  Cc: ast, daniel, kernel-team, peterz, Song Liu, KP Singh, Martin KaFai Lau

To access per-task data, BPF programs usually creates a hash table with
pid as the key. This is not ideal because:
 1. The user need to estimate the proper size of the hash table, which may
    be inaccurate;
 2. Big hash tables are slow;
 3. To clean up the data properly during task terminations, the user need
    to write extra logic.

Task local storage overcomes these issues and offers a better option for
these per-task data. Task local storage is only available to BPF_LSM. Now
enable it for tracing programs.

Unlike LSM programs, tracing programs can be called in IRQ contexts.
Helpers that access task local storage are updated to use
raw_spin_lock_irqsave() instead of raw_spin_lock_bh().

Tracing programs can attach to functions on the task free path, e.g.
exit_creds(). To avoid allocating task local storage after
bpf_task_storage_free(). bpf_task_storage_get() is updated to not allocate
new storage when the task is not refcounted (task->usage == 0).

Acked-by: KP Singh <kpsingh@kernel.org>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Song Liu <songliubraving@fb.com>
---
 include/linux/bpf.h            |  7 ++++++
 include/linux/bpf_lsm.h        | 22 -----------------
 include/linux/bpf_types.h      |  2 +-
 include/linux/sched.h          |  5 ++++
 kernel/bpf/Makefile            |  3 +--
 kernel/bpf/bpf_local_storage.c | 28 +++++++++++++---------
 kernel/bpf/bpf_lsm.c           |  4 ----
 kernel/bpf/bpf_task_storage.c  | 43 +++++++++-------------------------
 kernel/fork.c                  |  5 ++++
 kernel/trace/bpf_trace.c       |  4 ++++
 10 files changed, 51 insertions(+), 72 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index cccaef1088eae..e2cfc4809219c 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1499,6 +1499,7 @@ struct bpf_prog *bpf_prog_by_id(u32 id);
 struct bpf_link *bpf_link_by_id(u32 id);
 
 const struct bpf_func_proto *bpf_base_func_proto(enum bpf_func_id func_id);
+void bpf_task_storage_free(struct task_struct *task);
 #else /* !CONFIG_BPF_SYSCALL */
 static inline struct bpf_prog *bpf_prog_get(u32 ufd)
 {
@@ -1684,6 +1685,10 @@ bpf_base_func_proto(enum bpf_func_id func_id)
 {
 	return NULL;
 }
+
+static inline void bpf_task_storage_free(struct task_struct *task)
+{
+}
 #endif /* CONFIG_BPF_SYSCALL */
 
 void __bpf_free_used_btfs(struct bpf_prog_aux *aux,
@@ -1886,6 +1891,8 @@ extern const struct bpf_func_proto bpf_this_cpu_ptr_proto;
 extern const struct bpf_func_proto bpf_ktime_get_coarse_ns_proto;
 extern const struct bpf_func_proto bpf_sock_from_file_proto;
 extern const struct bpf_func_proto bpf_get_socket_ptr_cookie_proto;
+extern const struct bpf_func_proto bpf_task_storage_get_proto;
+extern const struct bpf_func_proto bpf_task_storage_delete_proto;
 
 const struct bpf_func_proto *bpf_tracing_func_proto(
 	enum bpf_func_id func_id, const struct bpf_prog *prog);
diff --git a/include/linux/bpf_lsm.h b/include/linux/bpf_lsm.h
index 0d1c33ace3987..479c101546ad1 100644
--- a/include/linux/bpf_lsm.h
+++ b/include/linux/bpf_lsm.h
@@ -38,21 +38,9 @@ static inline struct bpf_storage_blob *bpf_inode(
 	return inode->i_security + bpf_lsm_blob_sizes.lbs_inode;
 }
 
-static inline struct bpf_storage_blob *bpf_task(
-	const struct task_struct *task)
-{
-	if (unlikely(!task->security))
-		return NULL;
-
-	return task->security + bpf_lsm_blob_sizes.lbs_task;
-}
-
 extern const struct bpf_func_proto bpf_inode_storage_get_proto;
 extern const struct bpf_func_proto bpf_inode_storage_delete_proto;
-extern const struct bpf_func_proto bpf_task_storage_get_proto;
-extern const struct bpf_func_proto bpf_task_storage_delete_proto;
 void bpf_inode_storage_free(struct inode *inode);
-void bpf_task_storage_free(struct task_struct *task);
 
 #else /* !CONFIG_BPF_LSM */
 
@@ -73,20 +61,10 @@ static inline struct bpf_storage_blob *bpf_inode(
 	return NULL;
 }
 
-static inline struct bpf_storage_blob *bpf_task(
-	const struct task_struct *task)
-{
-	return NULL;
-}
-
 static inline void bpf_inode_storage_free(struct inode *inode)
 {
 }
 
-static inline void bpf_task_storage_free(struct task_struct *task)
-{
-}
-
 #endif /* CONFIG_BPF_LSM */
 
 #endif /* _LINUX_BPF_LSM_H */
diff --git a/include/linux/bpf_types.h b/include/linux/bpf_types.h
index 99f7fd657d87a..b9edee336d804 100644
--- a/include/linux/bpf_types.h
+++ b/include/linux/bpf_types.h
@@ -109,8 +109,8 @@ BPF_MAP_TYPE(BPF_MAP_TYPE_SOCKHASH, sock_hash_ops)
 #endif
 #ifdef CONFIG_BPF_LSM
 BPF_MAP_TYPE(BPF_MAP_TYPE_INODE_STORAGE, inode_storage_map_ops)
-BPF_MAP_TYPE(BPF_MAP_TYPE_TASK_STORAGE, task_storage_map_ops)
 #endif
+BPF_MAP_TYPE(BPF_MAP_TYPE_TASK_STORAGE, task_storage_map_ops)
 BPF_MAP_TYPE(BPF_MAP_TYPE_CPUMAP, cpu_map_ops)
 #if defined(CONFIG_XDP_SOCKETS)
 BPF_MAP_TYPE(BPF_MAP_TYPE_XSKMAP, xsk_map_ops)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 4d568288abf9f..e5fbf8e6952ab 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -42,6 +42,7 @@ struct audit_context;
 struct backing_dev_info;
 struct bio_list;
 struct blk_plug;
+struct bpf_local_storage;
 struct capture_control;
 struct cfs_rq;
 struct fs_struct;
@@ -1348,6 +1349,10 @@ struct task_struct {
 	/* Used by LSM modules for access restriction: */
 	void				*security;
 #endif
+#ifdef CONFIG_BPF_SYSCALL
+	/* Used by BPF task local storage */
+	struct bpf_local_storage __rcu	*bpf_storage;
+#endif
 
 #ifdef CONFIG_GCC_PLUGIN_STACKLEAK
 	unsigned long			lowest_stack;
diff --git a/kernel/bpf/Makefile b/kernel/bpf/Makefile
index d1249340fd6ba..7f33098ca63fb 100644
--- a/kernel/bpf/Makefile
+++ b/kernel/bpf/Makefile
@@ -9,8 +9,8 @@ CFLAGS_core.o += $(call cc-disable-warning, override-init) $(cflags-nogcse-yy)
 obj-$(CONFIG_BPF_SYSCALL) += syscall.o verifier.o inode.o helpers.o tnum.o bpf_iter.o map_iter.o task_iter.o prog_iter.o
 obj-$(CONFIG_BPF_SYSCALL) += hashtab.o arraymap.o percpu_freelist.o bpf_lru_list.o lpm_trie.o map_in_map.o
 obj-$(CONFIG_BPF_SYSCALL) += local_storage.o queue_stack_maps.o ringbuf.o
+obj-$(CONFIG_BPF_SYSCALL) += bpf_local_storage.o bpf_task_storage.o
 obj-${CONFIG_BPF_LSM}	  += bpf_inode_storage.o
-obj-${CONFIG_BPF_LSM}	  += bpf_task_storage.o
 obj-$(CONFIG_BPF_SYSCALL) += disasm.o
 obj-$(CONFIG_BPF_JIT) += trampoline.o
 obj-$(CONFIG_BPF_SYSCALL) += btf.o
@@ -18,7 +18,6 @@ obj-$(CONFIG_BPF_JIT) += dispatcher.o
 ifeq ($(CONFIG_NET),y)
 obj-$(CONFIG_BPF_SYSCALL) += devmap.o
 obj-$(CONFIG_BPF_SYSCALL) += cpumap.o
-obj-$(CONFIG_BPF_SYSCALL) += bpf_local_storage.o
 obj-$(CONFIG_BPF_SYSCALL) += offload.o
 obj-$(CONFIG_BPF_SYSCALL) += net_namespace.o
 endif
diff --git a/kernel/bpf/bpf_local_storage.c b/kernel/bpf/bpf_local_storage.c
index dd5aedee99e73..9bd47ad2b26f1 100644
--- a/kernel/bpf/bpf_local_storage.c
+++ b/kernel/bpf/bpf_local_storage.c
@@ -140,17 +140,18 @@ static void __bpf_selem_unlink_storage(struct bpf_local_storage_elem *selem)
 {
 	struct bpf_local_storage *local_storage;
 	bool free_local_storage = false;
+	unsigned long flags;
 
 	if (unlikely(!selem_linked_to_storage(selem)))
 		/* selem has already been unlinked from sk */
 		return;
 
 	local_storage = rcu_dereference(selem->local_storage);
-	raw_spin_lock_bh(&local_storage->lock);
+	raw_spin_lock_irqsave(&local_storage->lock, flags);
 	if (likely(selem_linked_to_storage(selem)))
 		free_local_storage = bpf_selem_unlink_storage_nolock(
 			local_storage, selem, true);
-	raw_spin_unlock_bh(&local_storage->lock);
+	raw_spin_unlock_irqrestore(&local_storage->lock, flags);
 
 	if (free_local_storage)
 		kfree_rcu(local_storage, rcu);
@@ -167,6 +168,7 @@ void bpf_selem_unlink_map(struct bpf_local_storage_elem *selem)
 {
 	struct bpf_local_storage_map *smap;
 	struct bpf_local_storage_map_bucket *b;
+	unsigned long flags;
 
 	if (unlikely(!selem_linked_to_map(selem)))
 		/* selem has already be unlinked from smap */
@@ -174,21 +176,22 @@ void bpf_selem_unlink_map(struct bpf_local_storage_elem *selem)
 
 	smap = rcu_dereference(SDATA(selem)->smap);
 	b = select_bucket(smap, selem);
-	raw_spin_lock_bh(&b->lock);
+	raw_spin_lock_irqsave(&b->lock, flags);
 	if (likely(selem_linked_to_map(selem)))
 		hlist_del_init_rcu(&selem->map_node);
-	raw_spin_unlock_bh(&b->lock);
+	raw_spin_unlock_irqrestore(&b->lock, flags);
 }
 
 void bpf_selem_link_map(struct bpf_local_storage_map *smap,
 			struct bpf_local_storage_elem *selem)
 {
 	struct bpf_local_storage_map_bucket *b = select_bucket(smap, selem);
+	unsigned long flags;
 
-	raw_spin_lock_bh(&b->lock);
+	raw_spin_lock_irqsave(&b->lock, flags);
 	RCU_INIT_POINTER(SDATA(selem)->smap, smap);
 	hlist_add_head_rcu(&selem->map_node, &b->list);
-	raw_spin_unlock_bh(&b->lock);
+	raw_spin_unlock_irqrestore(&b->lock, flags);
 }
 
 void bpf_selem_unlink(struct bpf_local_storage_elem *selem)
@@ -224,16 +227,18 @@ bpf_local_storage_lookup(struct bpf_local_storage *local_storage,
 
 	sdata = SDATA(selem);
 	if (cacheit_lockit) {
+		unsigned long flags;
+
 		/* spinlock is needed to avoid racing with the
 		 * parallel delete.  Otherwise, publishing an already
 		 * deleted sdata to the cache will become a use-after-free
 		 * problem in the next bpf_local_storage_lookup().
 		 */
-		raw_spin_lock_bh(&local_storage->lock);
+		raw_spin_lock_irqsave(&local_storage->lock, flags);
 		if (selem_linked_to_storage(selem))
 			rcu_assign_pointer(local_storage->cache[smap->cache_idx],
 					   sdata);
-		raw_spin_unlock_bh(&local_storage->lock);
+		raw_spin_unlock_irqrestore(&local_storage->lock, flags);
 	}
 
 	return sdata;
@@ -327,6 +332,7 @@ bpf_local_storage_update(void *owner, struct bpf_local_storage_map *smap,
 	struct bpf_local_storage_data *old_sdata = NULL;
 	struct bpf_local_storage_elem *selem;
 	struct bpf_local_storage *local_storage;
+	unsigned long flags;
 	int err;
 
 	/* BPF_EXIST and BPF_NOEXIST cannot be both set */
@@ -374,7 +380,7 @@ bpf_local_storage_update(void *owner, struct bpf_local_storage_map *smap,
 		}
 	}
 
-	raw_spin_lock_bh(&local_storage->lock);
+	raw_spin_lock_irqsave(&local_storage->lock, flags);
 
 	/* Recheck local_storage->list under local_storage->lock */
 	if (unlikely(hlist_empty(&local_storage->list))) {
@@ -428,11 +434,11 @@ bpf_local_storage_update(void *owner, struct bpf_local_storage_map *smap,
 	}
 
 unlock:
-	raw_spin_unlock_bh(&local_storage->lock);
+	raw_spin_unlock_irqrestore(&local_storage->lock, flags);
 	return SDATA(selem);
 
 unlock_err:
-	raw_spin_unlock_bh(&local_storage->lock);
+	raw_spin_unlock_irqrestore(&local_storage->lock, flags);
 	return ERR_PTR(err);
 }
 
diff --git a/kernel/bpf/bpf_lsm.c b/kernel/bpf/bpf_lsm.c
index 1622a44d1617e..9829f381b51c5 100644
--- a/kernel/bpf/bpf_lsm.c
+++ b/kernel/bpf/bpf_lsm.c
@@ -115,10 +115,6 @@ bpf_lsm_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 		return &bpf_spin_lock_proto;
 	case BPF_FUNC_spin_unlock:
 		return &bpf_spin_unlock_proto;
-	case BPF_FUNC_task_storage_get:
-		return &bpf_task_storage_get_proto;
-	case BPF_FUNC_task_storage_delete:
-		return &bpf_task_storage_delete_proto;
 	case BPF_FUNC_bprm_opts_set:
 		return &bpf_bprm_opts_set_proto;
 	case BPF_FUNC_ima_inode_hash:
diff --git a/kernel/bpf/bpf_task_storage.c b/kernel/bpf/bpf_task_storage.c
index e0da0258b732d..baf3566e23233 100644
--- a/kernel/bpf/bpf_task_storage.c
+++ b/kernel/bpf/bpf_task_storage.c
@@ -15,7 +15,6 @@
 #include <linux/bpf_local_storage.h>
 #include <linux/filter.h>
 #include <uapi/linux/btf.h>
-#include <linux/bpf_lsm.h>
 #include <linux/btf_ids.h>
 #include <linux/fdtable.h>
 
@@ -24,12 +23,8 @@ DEFINE_BPF_STORAGE_CACHE(task_cache);
 static struct bpf_local_storage __rcu **task_storage_ptr(void *owner)
 {
 	struct task_struct *task = owner;
-	struct bpf_storage_blob *bsb;
 
-	bsb = bpf_task(task);
-	if (!bsb)
-		return NULL;
-	return &bsb->storage;
+	return &task->bpf_storage;
 }
 
 static struct bpf_local_storage_data *
@@ -38,13 +33,8 @@ task_storage_lookup(struct task_struct *task, struct bpf_map *map,
 {
 	struct bpf_local_storage *task_storage;
 	struct bpf_local_storage_map *smap;
-	struct bpf_storage_blob *bsb;
-
-	bsb = bpf_task(task);
-	if (!bsb)
-		return NULL;
 
-	task_storage = rcu_dereference(bsb->storage);
+	task_storage = rcu_dereference(task->bpf_storage);
 	if (!task_storage)
 		return NULL;
 
@@ -57,16 +47,12 @@ void bpf_task_storage_free(struct task_struct *task)
 	struct bpf_local_storage_elem *selem;
 	struct bpf_local_storage *local_storage;
 	bool free_task_storage = false;
-	struct bpf_storage_blob *bsb;
 	struct hlist_node *n;
-
-	bsb = bpf_task(task);
-	if (!bsb)
-		return;
+	unsigned long flags;
 
 	rcu_read_lock();
 
-	local_storage = rcu_dereference(bsb->storage);
+	local_storage = rcu_dereference(task->bpf_storage);
 	if (!local_storage) {
 		rcu_read_unlock();
 		return;
@@ -81,7 +67,7 @@ void bpf_task_storage_free(struct task_struct *task)
 	 * when unlinking elem from the local_storage->list and
 	 * the map's bucket->list.
 	 */
-	raw_spin_lock_bh(&local_storage->lock);
+	raw_spin_lock_irqsave(&local_storage->lock, flags);
 	hlist_for_each_entry_safe(selem, n, &local_storage->list, snode) {
 		/* Always unlink from map before unlinking from
 		 * local_storage.
@@ -90,7 +76,7 @@ void bpf_task_storage_free(struct task_struct *task)
 		free_task_storage = bpf_selem_unlink_storage_nolock(
 			local_storage, selem, false);
 	}
-	raw_spin_unlock_bh(&local_storage->lock);
+	raw_spin_unlock_irqrestore(&local_storage->lock, flags);
 	rcu_read_unlock();
 
 	/* free_task_storage should always be true as long as
@@ -150,7 +136,7 @@ static int bpf_pid_task_storage_update_elem(struct bpf_map *map, void *key,
 	 */
 	WARN_ON_ONCE(!rcu_read_lock_held());
 	task = pid_task(pid, PIDTYPE_PID);
-	if (!task || !task_storage_ptr(task)) {
+	if (!task) {
 		err = -ENOENT;
 		goto out;
 	}
@@ -213,23 +199,16 @@ BPF_CALL_4(bpf_task_storage_get, struct bpf_map *, map, struct task_struct *,
 	if (flags & ~(BPF_LOCAL_STORAGE_GET_F_CREATE))
 		return (unsigned long)NULL;
 
-	/* explicitly check that the task_storage_ptr is not
-	 * NULL as task_storage_lookup returns NULL in this case and
-	 * bpf_local_storage_update expects the owner to have a
-	 * valid storage pointer.
-	 */
-	if (!task || !task_storage_ptr(task))
+	if (!task)
 		return (unsigned long)NULL;
 
 	sdata = task_storage_lookup(task, map, true);
 	if (sdata)
 		return (unsigned long)sdata->data;
 
-	/* This helper must only be called from places where the lifetime of the task
-	 * is guaranteed. Either by being refcounted or by being protected
-	 * by an RCU read-side critical section.
-	 */
-	if (flags & BPF_LOCAL_STORAGE_GET_F_CREATE) {
+	/* only allocate new storage, when the task is refcounted */
+	if (refcount_read(&task->usage) &&
+	    (flags & BPF_LOCAL_STORAGE_GET_F_CREATE)) {
 		sdata = bpf_local_storage_update(
 			task, (struct bpf_local_storage_map *)map, value,
 			BPF_NOEXIST);
diff --git a/kernel/fork.c b/kernel/fork.c
index d66cd1014211b..181604db2d65e 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -96,6 +96,7 @@
 #include <linux/kasan.h>
 #include <linux/scs.h>
 #include <linux/io_uring.h>
+#include <linux/bpf.h>
 
 #include <asm/pgalloc.h>
 #include <linux/uaccess.h>
@@ -734,6 +735,7 @@ void __put_task_struct(struct task_struct *tsk)
 	cgroup_free(tsk);
 	task_numa_free(tsk, true);
 	security_task_free(tsk);
+	bpf_task_storage_free(tsk);
 	exit_creds(tsk);
 	delayacct_tsk_free(tsk);
 	put_signal_struct(tsk->signal);
@@ -2062,6 +2064,9 @@ static __latent_entropy struct task_struct *copy_process(
 	p->sequential_io	= 0;
 	p->sequential_io_avg	= 0;
 #endif
+#ifdef CONFIG_BPF_SYSCALL
+	RCU_INIT_POINTER(p->bpf_storage, NULL);
+#endif
 
 	/* Perform scheduler related setup. Assign this task to a CPU. */
 	retval = sched_fork(clone_flags, p);
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index b0c45d923f0f9..e9701744d8e4c 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1367,6 +1367,10 @@ bpf_tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 		return &bpf_per_cpu_ptr_proto;
 	case BPF_FUNC_this_cpu_ptr:
 		return &bpf_this_cpu_ptr_proto;
+	case BPF_FUNC_task_storage_get:
+		return &bpf_task_storage_get_proto;
+	case BPF_FUNC_task_storage_delete:
+		return &bpf_task_storage_delete_proto;
 	default:
 		return NULL;
 	}
-- 
2.24.1


^ permalink raw reply	[flat|nested] 10+ messages in thread

* [PATCH v6 bpf-next 2/6] bpf: prevent deadlock from recursive bpf_task_storage_[get|delete]
  2021-02-25 23:43 [PATCH v6 bpf-next 0/6] bpf: enable task local storage for tracing programs Song Liu
  2021-02-25 23:43 ` [PATCH v6 bpf-next 1/6] " Song Liu
@ 2021-02-25 23:43 ` Song Liu
  2021-02-26  0:01   ` Martin KaFai Lau
  2021-02-25 23:43 ` [PATCH v6 bpf-next 3/6] selftests/bpf: add non-BPF_LSM test for task local storage Song Liu
                   ` (4 subsequent siblings)
  6 siblings, 1 reply; 10+ messages in thread
From: Song Liu @ 2021-02-25 23:43 UTC (permalink / raw)
  To: bpf, netdev, linux-kernel; +Cc: ast, daniel, kernel-team, peterz, Song Liu

BPF helpers bpf_task_storage_[get|delete] could hold two locks:
bpf_local_storage_map_bucket->lock and bpf_local_storage->lock. Calling
these helpers from fentry/fexit programs on functions in bpf_*_storage.c
may cause deadlock on either locks.

Prevent such deadlock with a per cpu counter, bpf_task_storage_busy. We
need this counter to be global, because the two locks here belong to two
different objects: bpf_local_storage_map and bpf_local_storage. If we
pick one of them as the owner of the counter, it is still possible to
trigger deadlock on the other lock. For example, if bpf_local_storage_map
owns the counters, it cannot prevent deadlock on bpf_local_storage->lock
when two maps are used.

Signed-off-by: Song Liu <songliubraving@fb.com>
---
 include/linux/bpf_local_storage.h |  3 +-
 kernel/bpf/bpf_inode_storage.c    |  2 +-
 kernel/bpf/bpf_local_storage.c    | 11 +++++-
 kernel/bpf/bpf_task_storage.c     | 59 ++++++++++++++++++++++++++-----
 net/core/bpf_sk_storage.c         |  2 +-
 5 files changed, 65 insertions(+), 12 deletions(-)

diff --git a/include/linux/bpf_local_storage.h b/include/linux/bpf_local_storage.h
index b2c9463f36a1b..b902c580c48d5 100644
--- a/include/linux/bpf_local_storage.h
+++ b/include/linux/bpf_local_storage.h
@@ -126,7 +126,8 @@ bpf_local_storage_lookup(struct bpf_local_storage *local_storage,
 			 struct bpf_local_storage_map *smap,
 			 bool cacheit_lockit);
 
-void bpf_local_storage_map_free(struct bpf_local_storage_map *smap);
+void bpf_local_storage_map_free(struct bpf_local_storage_map *smap,
+				int __percpu *busy_counter);
 
 int bpf_local_storage_map_check_btf(const struct bpf_map *map,
 				    const struct btf *btf,
diff --git a/kernel/bpf/bpf_inode_storage.c b/kernel/bpf/bpf_inode_storage.c
index 6639640523c0b..da753721457cb 100644
--- a/kernel/bpf/bpf_inode_storage.c
+++ b/kernel/bpf/bpf_inode_storage.c
@@ -237,7 +237,7 @@ static void inode_storage_map_free(struct bpf_map *map)
 
 	smap = (struct bpf_local_storage_map *)map;
 	bpf_local_storage_cache_idx_free(&inode_cache, smap->cache_idx);
-	bpf_local_storage_map_free(smap);
+	bpf_local_storage_map_free(smap, NULL);
 }
 
 static int inode_storage_map_btf_id;
diff --git a/kernel/bpf/bpf_local_storage.c b/kernel/bpf/bpf_local_storage.c
index 9bd47ad2b26f1..b305270b7a4bd 100644
--- a/kernel/bpf/bpf_local_storage.c
+++ b/kernel/bpf/bpf_local_storage.c
@@ -474,7 +474,8 @@ void bpf_local_storage_cache_idx_free(struct bpf_local_storage_cache *cache,
 	spin_unlock(&cache->idx_lock);
 }
 
-void bpf_local_storage_map_free(struct bpf_local_storage_map *smap)
+void bpf_local_storage_map_free(struct bpf_local_storage_map *smap,
+				int __percpu *busy_counter)
 {
 	struct bpf_local_storage_elem *selem;
 	struct bpf_local_storage_map_bucket *b;
@@ -503,7 +504,15 @@ void bpf_local_storage_map_free(struct bpf_local_storage_map *smap)
 		while ((selem = hlist_entry_safe(
 				rcu_dereference_raw(hlist_first_rcu(&b->list)),
 				struct bpf_local_storage_elem, map_node))) {
+			if (busy_counter) {
+				migrate_disable();
+				__this_cpu_inc(*busy_counter);
+			}
 			bpf_selem_unlink(selem);
+			if (busy_counter) {
+				__this_cpu_dec(*busy_counter);
+				migrate_enable();
+			}
 			cond_resched_rcu();
 		}
 		rcu_read_unlock();
diff --git a/kernel/bpf/bpf_task_storage.c b/kernel/bpf/bpf_task_storage.c
index baf3566e23233..fd3c74ef608ef 100644
--- a/kernel/bpf/bpf_task_storage.c
+++ b/kernel/bpf/bpf_task_storage.c
@@ -20,6 +20,31 @@
 
 DEFINE_BPF_STORAGE_CACHE(task_cache);
 
+DEFINE_PER_CPU(int, bpf_task_storage_busy);
+
+static void bpf_task_storage_lock(void)
+{
+	migrate_disable();
+	__this_cpu_inc(bpf_task_storage_busy);
+}
+
+static void bpf_task_storage_unlock(void)
+{
+	__this_cpu_dec(bpf_task_storage_busy);
+	migrate_enable();
+}
+
+static bool bpf_task_storage_trylock(void)
+{
+	migrate_disable();
+	if (unlikely(__this_cpu_inc_return(bpf_task_storage_busy) != 1)) {
+		__this_cpu_dec(bpf_task_storage_busy);
+		migrate_enable();
+		return false;
+	}
+	return true;
+}
+
 static struct bpf_local_storage __rcu **task_storage_ptr(void *owner)
 {
 	struct task_struct *task = owner;
@@ -67,6 +92,7 @@ void bpf_task_storage_free(struct task_struct *task)
 	 * when unlinking elem from the local_storage->list and
 	 * the map's bucket->list.
 	 */
+	bpf_task_storage_lock();
 	raw_spin_lock_irqsave(&local_storage->lock, flags);
 	hlist_for_each_entry_safe(selem, n, &local_storage->list, snode) {
 		/* Always unlink from map before unlinking from
@@ -77,6 +103,7 @@ void bpf_task_storage_free(struct task_struct *task)
 			local_storage, selem, false);
 	}
 	raw_spin_unlock_irqrestore(&local_storage->lock, flags);
+	bpf_task_storage_unlock();
 	rcu_read_unlock();
 
 	/* free_task_storage should always be true as long as
@@ -109,7 +136,9 @@ static void *bpf_pid_task_storage_lookup_elem(struct bpf_map *map, void *key)
 		goto out;
 	}
 
+	bpf_task_storage_lock();
 	sdata = task_storage_lookup(task, map, true);
+	bpf_task_storage_unlock();
 	put_pid(pid);
 	return sdata ? sdata->data : NULL;
 out:
@@ -141,8 +170,10 @@ static int bpf_pid_task_storage_update_elem(struct bpf_map *map, void *key,
 		goto out;
 	}
 
+	bpf_task_storage_lock();
 	sdata = bpf_local_storage_update(
 		task, (struct bpf_local_storage_map *)map, value, map_flags);
+	bpf_task_storage_unlock();
 
 	err = PTR_ERR_OR_ZERO(sdata);
 out:
@@ -185,7 +216,9 @@ static int bpf_pid_task_storage_delete_elem(struct bpf_map *map, void *key)
 		goto out;
 	}
 
+	bpf_task_storage_lock();
 	err = task_storage_delete(task, map);
+	bpf_task_storage_unlock();
 out:
 	put_pid(pid);
 	return err;
@@ -202,34 +235,44 @@ BPF_CALL_4(bpf_task_storage_get, struct bpf_map *, map, struct task_struct *,
 	if (!task)
 		return (unsigned long)NULL;
 
+	if (!bpf_task_storage_trylock())
+		return (unsigned long)NULL;
+
 	sdata = task_storage_lookup(task, map, true);
 	if (sdata)
-		return (unsigned long)sdata->data;
+		goto unlock;
 
 	/* only allocate new storage, when the task is refcounted */
 	if (refcount_read(&task->usage) &&
-	    (flags & BPF_LOCAL_STORAGE_GET_F_CREATE)) {
+	    (flags & BPF_LOCAL_STORAGE_GET_F_CREATE))
 		sdata = bpf_local_storage_update(
 			task, (struct bpf_local_storage_map *)map, value,
 			BPF_NOEXIST);
-		return IS_ERR(sdata) ? (unsigned long)NULL :
-					     (unsigned long)sdata->data;
-	}
 
-	return (unsigned long)NULL;
+unlock:
+	bpf_task_storage_unlock();
+	return IS_ERR_OR_NULL(sdata) ? (unsigned long)NULL :
+		(unsigned long)sdata->data;
 }
 
 BPF_CALL_2(bpf_task_storage_delete, struct bpf_map *, map, struct task_struct *,
 	   task)
 {
+	int ret;
+
 	if (!task)
 		return -EINVAL;
 
+	if (!bpf_task_storage_trylock())
+		return -EBUSY;
+
 	/* This helper must only be called from places where the lifetime of the task
 	 * is guaranteed. Either by being refcounted or by being protected
 	 * by an RCU read-side critical section.
 	 */
-	return task_storage_delete(task, map);
+	ret = task_storage_delete(task, map);
+	bpf_task_storage_unlock();
+	return ret;
 }
 
 static int notsupp_get_next_key(struct bpf_map *map, void *key, void *next_key)
@@ -255,7 +298,7 @@ static void task_storage_map_free(struct bpf_map *map)
 
 	smap = (struct bpf_local_storage_map *)map;
 	bpf_local_storage_cache_idx_free(&task_cache, smap->cache_idx);
-	bpf_local_storage_map_free(smap);
+	bpf_local_storage_map_free(smap, &bpf_task_storage_busy);
 }
 
 static int task_storage_map_btf_id;
diff --git a/net/core/bpf_sk_storage.c b/net/core/bpf_sk_storage.c
index 4edd033e899c0..cc3712ad8716f 100644
--- a/net/core/bpf_sk_storage.c
+++ b/net/core/bpf_sk_storage.c
@@ -89,7 +89,7 @@ static void bpf_sk_storage_map_free(struct bpf_map *map)
 
 	smap = (struct bpf_local_storage_map *)map;
 	bpf_local_storage_cache_idx_free(&sk_cache, smap->cache_idx);
-	bpf_local_storage_map_free(smap);
+	bpf_local_storage_map_free(smap, NULL);
 }
 
 static struct bpf_map *bpf_sk_storage_map_alloc(union bpf_attr *attr)
-- 
2.24.1


^ permalink raw reply	[flat|nested] 10+ messages in thread

* [PATCH v6 bpf-next 3/6] selftests/bpf: add non-BPF_LSM test for task local storage
  2021-02-25 23:43 [PATCH v6 bpf-next 0/6] bpf: enable task local storage for tracing programs Song Liu
  2021-02-25 23:43 ` [PATCH v6 bpf-next 1/6] " Song Liu
  2021-02-25 23:43 ` [PATCH v6 bpf-next 2/6] bpf: prevent deadlock from recursive bpf_task_storage_[get|delete] Song Liu
@ 2021-02-25 23:43 ` Song Liu
  2021-02-25 23:43 ` [PATCH v6 bpf-next 4/6] selftests/bpf: test deadlock from recursive bpf_task_storage_[get|delete] Song Liu
                   ` (3 subsequent siblings)
  6 siblings, 0 replies; 10+ messages in thread
From: Song Liu @ 2021-02-25 23:43 UTC (permalink / raw)
  To: bpf, netdev, linux-kernel; +Cc: ast, daniel, kernel-team, peterz, Song Liu

Task local storage is enabled for tracing programs. Add two tests for
task local storage without CONFIG_BPF_LSM.

The first test stores a value in sys_enter and read it back in sys_exit.

The second test checks whether the kernel allows allocating task local
storage in exit_creds() (which it should not).

Signed-off-by: Song Liu <songliubraving@fb.com>
---
 .../bpf/prog_tests/task_local_storage.c       | 69 +++++++++++++++++++
 .../selftests/bpf/progs/task_local_storage.c  | 64 +++++++++++++++++
 .../bpf/progs/task_local_storage_exit_creds.c | 32 +++++++++
 3 files changed, 165 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/task_local_storage.c
 create mode 100644 tools/testing/selftests/bpf/progs/task_local_storage.c
 create mode 100644 tools/testing/selftests/bpf/progs/task_local_storage_exit_creds.c

diff --git a/tools/testing/selftests/bpf/prog_tests/task_local_storage.c b/tools/testing/selftests/bpf/prog_tests/task_local_storage.c
new file mode 100644
index 0000000000000..dbb7525cdd567
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/task_local_storage.c
@@ -0,0 +1,69 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook */
+
+#define _GNU_SOURCE         /* See feature_test_macros(7) */
+#include <unistd.h>
+#include <sys/syscall.h>   /* For SYS_xxx definitions */
+#include <sys/types.h>
+#include <test_progs.h>
+#include "task_local_storage.skel.h"
+#include "task_local_storage_exit_creds.skel.h"
+
+static void test_sys_enter_exit(void)
+{
+	struct task_local_storage *skel;
+	int err;
+
+	skel = task_local_storage__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "skel_open_and_load"))
+		return;
+
+	skel->bss->target_pid = syscall(SYS_gettid);
+
+	err = task_local_storage__attach(skel);
+	if (!ASSERT_OK(err, "skel_attach"))
+		goto out;
+
+	syscall(SYS_gettid);
+	syscall(SYS_gettid);
+
+	/* 3x syscalls: 1x attach and 2x gettid */
+	ASSERT_EQ(skel->bss->enter_cnt, 3, "enter_cnt");
+	ASSERT_EQ(skel->bss->exit_cnt, 3, "exit_cnt");
+	ASSERT_EQ(skel->bss->mismatch_cnt, 0, "mismatch_cnt");
+out:
+	task_local_storage__destroy(skel);
+}
+
+static void test_exit_creds(void)
+{
+	struct task_local_storage_exit_creds *skel;
+	int err;
+
+	skel = task_local_storage_exit_creds__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "skel_open_and_load"))
+		return;
+
+	err = task_local_storage_exit_creds__attach(skel);
+	if (!ASSERT_OK(err, "skel_attach"))
+		goto out;
+
+	/* trigger at least one exit_creds() */
+	if (CHECK_FAIL(system("ls > /dev/null")))
+		goto out;
+
+	/* sync rcu to make sure exit_creds() is called for "ls" */
+	kern_sync_rcu();
+	ASSERT_EQ(skel->bss->valid_ptr_count, 0, "valid_ptr_count");
+	ASSERT_NEQ(skel->bss->null_ptr_count, 0, "null_ptr_count");
+out:
+	task_local_storage_exit_creds__destroy(skel);
+}
+
+void test_task_local_storage(void)
+{
+	if (test__start_subtest("sys_enter_exit"))
+		test_sys_enter_exit();
+	if (test__start_subtest("exit_creds"))
+		test_exit_creds();
+}
diff --git a/tools/testing/selftests/bpf/progs/task_local_storage.c b/tools/testing/selftests/bpf/progs/task_local_storage.c
new file mode 100644
index 0000000000000..80a0a20db88d2
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/task_local_storage.c
@@ -0,0 +1,64 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook */
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+char _license[] SEC("license") = "GPL";
+
+struct {
+	__uint(type, BPF_MAP_TYPE_TASK_STORAGE);
+	__uint(map_flags, BPF_F_NO_PREALLOC);
+	__type(key, int);
+	__type(value, long);
+} enter_id SEC(".maps");
+
+#define MAGIC_VALUE 0xabcd1234
+
+pid_t target_pid = 0;
+int mismatch_cnt = 0;
+int enter_cnt = 0;
+int exit_cnt = 0;
+
+SEC("tp_btf/sys_enter")
+int BPF_PROG(on_enter, struct pt_regs *regs, long id)
+{
+	struct task_struct *task;
+	long *ptr;
+
+	task = bpf_get_current_task_btf();
+	if (task->pid != target_pid)
+		return 0;
+
+	ptr = bpf_task_storage_get(&enter_id, task, 0,
+				   BPF_LOCAL_STORAGE_GET_F_CREATE);
+	if (!ptr)
+		return 0;
+
+	__sync_fetch_and_add(&enter_cnt, 1);
+	*ptr = MAGIC_VALUE + enter_cnt;
+
+	return 0;
+}
+
+SEC("tp_btf/sys_exit")
+int BPF_PROG(on_exit, struct pt_regs *regs, long id)
+{
+	struct task_struct *task;
+	long *ptr;
+
+	task = bpf_get_current_task_btf();
+	if (task->pid != target_pid)
+		return 0;
+
+	ptr = bpf_task_storage_get(&enter_id, task, 0,
+				   BPF_LOCAL_STORAGE_GET_F_CREATE);
+	if (!ptr)
+		return 0;
+
+	__sync_fetch_and_add(&exit_cnt, 1);
+	if (*ptr != MAGIC_VALUE + exit_cnt)
+		__sync_fetch_and_add(&mismatch_cnt, 1);
+	return 0;
+}
diff --git a/tools/testing/selftests/bpf/progs/task_local_storage_exit_creds.c b/tools/testing/selftests/bpf/progs/task_local_storage_exit_creds.c
new file mode 100644
index 0000000000000..81758c0aef993
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/task_local_storage_exit_creds.c
@@ -0,0 +1,32 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook */
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+char _license[] SEC("license") = "GPL";
+
+struct {
+	__uint(type, BPF_MAP_TYPE_TASK_STORAGE);
+	__uint(map_flags, BPF_F_NO_PREALLOC);
+	__type(key, int);
+	__type(value, __u64);
+} task_storage SEC(".maps");
+
+int valid_ptr_count = 0;
+int null_ptr_count = 0;
+
+SEC("fentry/exit_creds")
+int BPF_PROG(trace_exit_creds, struct task_struct *task)
+{
+	__u64 *ptr;
+
+	ptr = bpf_task_storage_get(&task_storage, task, 0,
+				   BPF_LOCAL_STORAGE_GET_F_CREATE);
+	if (ptr)
+		__sync_fetch_and_add(&valid_ptr_count, 1);
+	else
+		__sync_fetch_and_add(&null_ptr_count, 1);
+	return 0;
+}
-- 
2.24.1


^ permalink raw reply	[flat|nested] 10+ messages in thread

* [PATCH v6 bpf-next 4/6] selftests/bpf: test deadlock from recursive bpf_task_storage_[get|delete]
  2021-02-25 23:43 [PATCH v6 bpf-next 0/6] bpf: enable task local storage for tracing programs Song Liu
                   ` (2 preceding siblings ...)
  2021-02-25 23:43 ` [PATCH v6 bpf-next 3/6] selftests/bpf: add non-BPF_LSM test for task local storage Song Liu
@ 2021-02-25 23:43 ` Song Liu
  2021-02-25 23:43 ` [PATCH v6 bpf-next 5/6] bpf: runqslower: prefer using local vmlimux to generate vmlinux.h Song Liu
                   ` (2 subsequent siblings)
  6 siblings, 0 replies; 10+ messages in thread
From: Song Liu @ 2021-02-25 23:43 UTC (permalink / raw)
  To: bpf, netdev, linux-kernel; +Cc: ast, daniel, kernel-team, peterz, Song Liu

Add a test with recursive bpf_task_storage_[get|delete] from fentry
programs on bpf_local_storage_lookup and bpf_local_storage_update. Without
proper deadlock prevent mechanism, this test would cause deadlock.

Signed-off-by: Song Liu <songliubraving@fb.com>
---
 .../bpf/prog_tests/task_local_storage.c       | 23 ++++++
 .../selftests/bpf/progs/task_ls_recursion.c   | 70 +++++++++++++++++++
 2 files changed, 93 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/progs/task_ls_recursion.c

diff --git a/tools/testing/selftests/bpf/prog_tests/task_local_storage.c b/tools/testing/selftests/bpf/prog_tests/task_local_storage.c
index dbb7525cdd567..035c263aab1b1 100644
--- a/tools/testing/selftests/bpf/prog_tests/task_local_storage.c
+++ b/tools/testing/selftests/bpf/prog_tests/task_local_storage.c
@@ -8,6 +8,7 @@
 #include <test_progs.h>
 #include "task_local_storage.skel.h"
 #include "task_local_storage_exit_creds.skel.h"
+#include "task_ls_recursion.skel.h"
 
 static void test_sys_enter_exit(void)
 {
@@ -60,10 +61,32 @@ static void test_exit_creds(void)
 	task_local_storage_exit_creds__destroy(skel);
 }
 
+static void test_recursion(void)
+{
+	struct task_ls_recursion *skel;
+	int err;
+
+	skel = task_ls_recursion__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "skel_open_and_load"))
+		return;
+
+	err = task_ls_recursion__attach(skel);
+	if (!ASSERT_OK(err, "skel_attach"))
+		goto out;
+
+	/* trigger sys_enter, make sure it does not cause deadlock */
+	syscall(SYS_gettid);
+
+out:
+	task_ls_recursion__destroy(skel);
+}
+
 void test_task_local_storage(void)
 {
 	if (test__start_subtest("sys_enter_exit"))
 		test_sys_enter_exit();
 	if (test__start_subtest("exit_creds"))
 		test_exit_creds();
+	if (test__start_subtest("recursion"))
+		test_recursion();
 }
diff --git a/tools/testing/selftests/bpf/progs/task_ls_recursion.c b/tools/testing/selftests/bpf/progs/task_ls_recursion.c
new file mode 100644
index 0000000000000..564583dca7c85
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/task_ls_recursion.c
@@ -0,0 +1,70 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook */
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+char _license[] SEC("license") = "GPL";
+
+struct {
+	__uint(type, BPF_MAP_TYPE_TASK_STORAGE);
+	__uint(map_flags, BPF_F_NO_PREALLOC);
+	__type(key, int);
+	__type(value, long);
+} map_a SEC(".maps");
+
+struct {
+	__uint(type, BPF_MAP_TYPE_TASK_STORAGE);
+	__uint(map_flags, BPF_F_NO_PREALLOC);
+	__type(key, int);
+	__type(value, long);
+} map_b SEC(".maps");
+
+SEC("fentry/bpf_local_storage_lookup")
+int BPF_PROG(on_lookup)
+{
+	struct task_struct *task = bpf_get_current_task_btf();
+
+	bpf_task_storage_delete(&map_a, task);
+	bpf_task_storage_delete(&map_b, task);
+	return 0;
+}
+
+SEC("fentry/bpf_local_storage_update")
+int BPF_PROG(on_update)
+{
+	struct task_struct *task = bpf_get_current_task_btf();
+	long *ptr;
+
+	ptr = bpf_task_storage_get(&map_a, task, 0,
+				   BPF_LOCAL_STORAGE_GET_F_CREATE);
+	if (ptr)
+		*ptr += 1;
+
+	ptr = bpf_task_storage_get(&map_b, task, 0,
+				   BPF_LOCAL_STORAGE_GET_F_CREATE);
+	if (ptr)
+		*ptr += 1;
+
+	return 0;
+}
+
+SEC("tp_btf/sys_enter")
+int BPF_PROG(on_enter, struct pt_regs *regs, long id)
+{
+	struct task_struct *task;
+	long *ptr;
+
+	task = bpf_get_current_task_btf();
+	ptr = bpf_task_storage_get(&map_a, task, 0,
+				   BPF_LOCAL_STORAGE_GET_F_CREATE);
+	if (ptr)
+		*ptr = 200;
+
+	ptr = bpf_task_storage_get(&map_b, task, 0,
+				   BPF_LOCAL_STORAGE_GET_F_CREATE);
+	if (ptr)
+		*ptr = 100;
+	return 0;
+}
-- 
2.24.1


^ permalink raw reply	[flat|nested] 10+ messages in thread

* [PATCH v6 bpf-next 5/6] bpf: runqslower: prefer using local vmlimux to generate vmlinux.h
  2021-02-25 23:43 [PATCH v6 bpf-next 0/6] bpf: enable task local storage for tracing programs Song Liu
                   ` (3 preceding siblings ...)
  2021-02-25 23:43 ` [PATCH v6 bpf-next 4/6] selftests/bpf: test deadlock from recursive bpf_task_storage_[get|delete] Song Liu
@ 2021-02-25 23:43 ` Song Liu
  2021-02-25 23:43 ` [PATCH v6 bpf-next 6/6] bpf: runqslower: use task local storage Song Liu
  2021-02-26  0:03 ` [PATCH v6 bpf-next 0/6] bpf: enable task local storage for tracing programs Martin KaFai Lau
  6 siblings, 0 replies; 10+ messages in thread
From: Song Liu @ 2021-02-25 23:43 UTC (permalink / raw)
  To: bpf, netdev, linux-kernel
  Cc: ast, daniel, kernel-team, peterz, Song Liu, Andrii Nakryiko

Update the Makefile to prefer using $(O)/vmlinux, $(KBUILD_OUTPUT)/vmlinux
(for selftests) or ../../../vmlinux. These two files should have latest
definitions for vmlinux.h.

Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Song Liu <songliubraving@fb.com>
---
 tools/bpf/runqslower/Makefile | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/tools/bpf/runqslower/Makefile b/tools/bpf/runqslower/Makefile
index 9d9fb6209be1b..c96ba90c6f018 100644
--- a/tools/bpf/runqslower/Makefile
+++ b/tools/bpf/runqslower/Makefile
@@ -16,7 +16,10 @@ CFLAGS := -g -Wall
 
 # Try to detect best kernel BTF source
 KERNEL_REL := $(shell uname -r)
-VMLINUX_BTF_PATHS := /sys/kernel/btf/vmlinux /boot/vmlinux-$(KERNEL_REL)
+VMLINUX_BTF_PATHS := $(if $(O),$(O)/vmlinux)		\
+	$(if $(KBUILD_OUTPUT),$(KBUILD_OUTPUT)/vmlinux) \
+	../../../vmlinux /sys/kernel/btf/vmlinux	\
+	/boot/vmlinux-$(KERNEL_REL)
 VMLINUX_BTF_PATH := $(or $(VMLINUX_BTF),$(firstword			       \
 					  $(wildcard $(VMLINUX_BTF_PATHS))))
 
-- 
2.24.1


^ permalink raw reply	[flat|nested] 10+ messages in thread

* [PATCH v6 bpf-next 6/6] bpf: runqslower: use task local storage
  2021-02-25 23:43 [PATCH v6 bpf-next 0/6] bpf: enable task local storage for tracing programs Song Liu
                   ` (4 preceding siblings ...)
  2021-02-25 23:43 ` [PATCH v6 bpf-next 5/6] bpf: runqslower: prefer using local vmlimux to generate vmlinux.h Song Liu
@ 2021-02-25 23:43 ` Song Liu
  2021-02-26  0:03 ` [PATCH v6 bpf-next 0/6] bpf: enable task local storage for tracing programs Martin KaFai Lau
  6 siblings, 0 replies; 10+ messages in thread
From: Song Liu @ 2021-02-25 23:43 UTC (permalink / raw)
  To: bpf, netdev, linux-kernel
  Cc: ast, daniel, kernel-team, peterz, Song Liu, Andrii Nakryiko

Replace hashtab with task local storage in runqslower. This improves the
performance of these BPF programs. The following table summarizes average
runtime of these programs, in nanoseconds:

                          task-local   hash-prealloc   hash-no-prealloc
handle__sched_wakeup             125             340               3124
handle__sched_wakeup_new        2812            1510               2998
handle__sched_switch             151             208                991

Note that, task local storage gives better performance than hashtab for
handle__sched_wakeup and handle__sched_switch. On the other hand, for
handle__sched_wakeup_new, task local storage is slower than hashtab with
prealloc. This is because handle__sched_wakeup_new accesses the data for
the first time, so it has to allocate the data for task local storage.
Once the initial allocation is done, subsequent accesses, as those in
handle__sched_wakeup, are much faster with task local storage. If we
disable hashtab prealloc, task local storage is much faster for all 3
functions.

Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Song Liu <songliubraving@fb.com>
---
 tools/bpf/runqslower/runqslower.bpf.c | 33 +++++++++++++++++----------
 1 file changed, 21 insertions(+), 12 deletions(-)

diff --git a/tools/bpf/runqslower/runqslower.bpf.c b/tools/bpf/runqslower/runqslower.bpf.c
index 1f18a409f0443..645530ca7e985 100644
--- a/tools/bpf/runqslower/runqslower.bpf.c
+++ b/tools/bpf/runqslower/runqslower.bpf.c
@@ -11,9 +11,9 @@ const volatile __u64 min_us = 0;
 const volatile pid_t targ_pid = 0;
 
 struct {
-	__uint(type, BPF_MAP_TYPE_HASH);
-	__uint(max_entries, 10240);
-	__type(key, u32);
+	__uint(type, BPF_MAP_TYPE_TASK_STORAGE);
+	__uint(map_flags, BPF_F_NO_PREALLOC);
+	__type(key, int);
 	__type(value, u64);
 } start SEC(".maps");
 
@@ -25,15 +25,20 @@ struct {
 
 /* record enqueue timestamp */
 __always_inline
-static int trace_enqueue(u32 tgid, u32 pid)
+static int trace_enqueue(struct task_struct *t)
 {
-	u64 ts;
+	u32 pid = t->pid;
+	u64 *ptr;
 
 	if (!pid || (targ_pid && targ_pid != pid))
 		return 0;
 
-	ts = bpf_ktime_get_ns();
-	bpf_map_update_elem(&start, &pid, &ts, 0);
+	ptr = bpf_task_storage_get(&start, t, 0,
+				   BPF_LOCAL_STORAGE_GET_F_CREATE);
+	if (!ptr)
+		return 0;
+
+	*ptr = bpf_ktime_get_ns();
 	return 0;
 }
 
@@ -43,7 +48,7 @@ int handle__sched_wakeup(u64 *ctx)
 	/* TP_PROTO(struct task_struct *p) */
 	struct task_struct *p = (void *)ctx[0];
 
-	return trace_enqueue(p->tgid, p->pid);
+	return trace_enqueue(p);
 }
 
 SEC("tp_btf/sched_wakeup_new")
@@ -52,7 +57,7 @@ int handle__sched_wakeup_new(u64 *ctx)
 	/* TP_PROTO(struct task_struct *p) */
 	struct task_struct *p = (void *)ctx[0];
 
-	return trace_enqueue(p->tgid, p->pid);
+	return trace_enqueue(p);
 }
 
 SEC("tp_btf/sched_switch")
@@ -70,12 +75,16 @@ int handle__sched_switch(u64 *ctx)
 
 	/* ivcsw: treat like an enqueue event and store timestamp */
 	if (prev->state == TASK_RUNNING)
-		trace_enqueue(prev->tgid, prev->pid);
+		trace_enqueue(prev);
 
 	pid = next->pid;
 
+	/* For pid mismatch, save a bpf_task_storage_get */
+	if (!pid || (targ_pid && targ_pid != pid))
+		return 0;
+
 	/* fetch timestamp and calculate delta */
-	tsp = bpf_map_lookup_elem(&start, &pid);
+	tsp = bpf_task_storage_get(&start, next, 0, 0);
 	if (!tsp)
 		return 0;   /* missed enqueue */
 
@@ -91,7 +100,7 @@ int handle__sched_switch(u64 *ctx)
 	bpf_perf_event_output(ctx, &events, BPF_F_CURRENT_CPU,
 			      &event, sizeof(event));
 
-	bpf_map_delete_elem(&start, &pid);
+	bpf_task_storage_delete(&start, next);
 	return 0;
 }
 
-- 
2.24.1


^ permalink raw reply	[flat|nested] 10+ messages in thread

* Re: [PATCH v6 bpf-next 2/6] bpf: prevent deadlock from recursive bpf_task_storage_[get|delete]
  2021-02-25 23:43 ` [PATCH v6 bpf-next 2/6] bpf: prevent deadlock from recursive bpf_task_storage_[get|delete] Song Liu
@ 2021-02-26  0:01   ` Martin KaFai Lau
  0 siblings, 0 replies; 10+ messages in thread
From: Martin KaFai Lau @ 2021-02-26  0:01 UTC (permalink / raw)
  To: Song Liu; +Cc: bpf, netdev, linux-kernel, ast, daniel, kernel-team, peterz

On Thu, Feb 25, 2021 at 03:43:15PM -0800, Song Liu wrote:
> BPF helpers bpf_task_storage_[get|delete] could hold two locks:
> bpf_local_storage_map_bucket->lock and bpf_local_storage->lock. Calling
> these helpers from fentry/fexit programs on functions in bpf_*_storage.c
> may cause deadlock on either locks.
> 
> Prevent such deadlock with a per cpu counter, bpf_task_storage_busy. We
> need this counter to be global, because the two locks here belong to two
> different objects: bpf_local_storage_map and bpf_local_storage. If we
> pick one of them as the owner of the counter, it is still possible to
> trigger deadlock on the other lock. For example, if bpf_local_storage_map
> owns the counters, it cannot prevent deadlock on bpf_local_storage->lock
> when two maps are used.
Acked-by: Martin KaFai Lau <kafai@fb.com>

^ permalink raw reply	[flat|nested] 10+ messages in thread

* Re: [PATCH v6 bpf-next 0/6] bpf: enable task local storage for tracing programs
  2021-02-25 23:43 [PATCH v6 bpf-next 0/6] bpf: enable task local storage for tracing programs Song Liu
                   ` (5 preceding siblings ...)
  2021-02-25 23:43 ` [PATCH v6 bpf-next 6/6] bpf: runqslower: use task local storage Song Liu
@ 2021-02-26  0:03 ` Martin KaFai Lau
  2021-02-26 20:03   ` Alexei Starovoitov
  6 siblings, 1 reply; 10+ messages in thread
From: Martin KaFai Lau @ 2021-02-26  0:03 UTC (permalink / raw)
  To: Song Liu; +Cc: bpf, netdev, linux-kernel, ast, daniel, kernel-team, peterz

On Thu, Feb 25, 2021 at 03:43:13PM -0800, Song Liu wrote:
> This set enables task local storage for non-BPF_LSM programs.
> 
> It is common for tracing BPF program to access per-task data. Currently,
> these data are stored in hash tables with pid as the key. In
> bcc/libbpftools [1], 9 out of 23 tools use such hash tables. However,
> hash table is not ideal for many use case. Task local storage provides
> better usability and performance for BPF programs. Please refer to 6/6 for
> some performance comparison of task local storage vs. hash table.
Thanks for the patches.

Acked-by: Martin KaFai Lau <kafai@fb.com>

^ permalink raw reply	[flat|nested] 10+ messages in thread

* Re: [PATCH v6 bpf-next 0/6] bpf: enable task local storage for tracing programs
  2021-02-26  0:03 ` [PATCH v6 bpf-next 0/6] bpf: enable task local storage for tracing programs Martin KaFai Lau
@ 2021-02-26 20:03   ` Alexei Starovoitov
  0 siblings, 0 replies; 10+ messages in thread
From: Alexei Starovoitov @ 2021-02-26 20:03 UTC (permalink / raw)
  To: Martin KaFai Lau
  Cc: Song Liu, bpf, Network Development, LKML, Alexei Starovoitov,
	Daniel Borkmann, Kernel Team, Peter Zijlstra

On Thu, Feb 25, 2021 at 4:04 PM Martin KaFai Lau <kafai@fb.com> wrote:
>
> On Thu, Feb 25, 2021 at 03:43:13PM -0800, Song Liu wrote:
> > This set enables task local storage for non-BPF_LSM programs.
> >
> > It is common for tracing BPF program to access per-task data. Currently,
> > these data are stored in hash tables with pid as the key. In
> > bcc/libbpftools [1], 9 out of 23 tools use such hash tables. However,
> > hash table is not ideal for many use case. Task local storage provides
> > better usability and performance for BPF programs. Please refer to 6/6 for
> > some performance comparison of task local storage vs. hash table.
> Thanks for the patches.
>
> Acked-by: Martin KaFai Lau <kafai@fb.com>

Applied. Thanks.

9 out of 23 libbpf-tools will significantly reduce the tracing overhead. Hooray!

^ permalink raw reply	[flat|nested] 10+ messages in thread

end of thread, other threads:[~2021-02-26 20:04 UTC | newest]

Thread overview: 10+ messages (download: mbox.gz / follow: Atom feed)
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2021-02-25 23:43 ` [PATCH v6 bpf-next 2/6] bpf: prevent deadlock from recursive bpf_task_storage_[get|delete] Song Liu
2021-02-26  0:01   ` Martin KaFai Lau
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2021-02-25 23:43 ` [PATCH v6 bpf-next 5/6] bpf: runqslower: prefer using local vmlimux to generate vmlinux.h Song Liu
2021-02-25 23:43 ` [PATCH v6 bpf-next 6/6] bpf: runqslower: use task local storage Song Liu
2021-02-26  0:03 ` [PATCH v6 bpf-next 0/6] bpf: enable task local storage for tracing programs Martin KaFai Lau
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