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bpf: Implement task local storage

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Similar to bpf_local_storage for sockets and inodes add local storage
for task_struct.

The life-cycle of storage is managed with the life-cycle of the
task_struct.  i.e. the storage is destroyed along with the owning task
with a callback to the bpf_task_storage_free from the task_free LSM
hook.

The BPF LSM allocates an __rcu pointer to the bpf_local_storage in
the security blob which are now stackable and can co-exist with other
LSMs.

The userspace map operations can be done by using a pid fd as a key
passed to the lookup, update and delete operations.

Signed-off-by: KP Singh <kpsingh@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20201106103747.2780972-3-kpsingh@chromium.org
This commit is contained in:
KP Singh
2020-11-06 10:37:40 +00:00
committed by Alexei Starovoitov
parent 9e7a4d9831
commit 4cf1bc1f10
10 changed files with 436 additions and 1 deletions
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39
tools/include/uapi/linux/bpf.h
View File

@@ -157,6 +157,7 @@ enum bpf_map_type {
BPF_MAP_TYPE_STRUCT_OPS,
BPF_MAP_TYPE_RINGBUF,
BPF_MAP_TYPE_INODE_STORAGE,
BPF_MAP_TYPE_TASK_STORAGE,
};
/* Note that tracing related programs such as
@@ -3742,6 +3743,42 @@ union bpf_attr {
* Return
* The helper returns **TC_ACT_REDIRECT** on success or
* **TC_ACT_SHOT** on error.
*
* void *bpf_task_storage_get(struct bpf_map *map, struct task_struct *task, void *value, u64 flags)
* Description
* Get a bpf_local_storage from the *task*.
*
* Logically, it could be thought of as getting the value from
* a *map* with *task* as the **key**. From this
* perspective, the usage is not much different from
* **bpf_map_lookup_elem**\ (*map*, **&**\ *task*) except this
* helper enforces the key must be an task_struct and the map must also
* be a **BPF_MAP_TYPE_TASK_STORAGE**.
*
* Underneath, the value is stored locally at *task* instead of
* the *map*. The *map* is used as the bpf-local-storage
* "type". The bpf-local-storage "type" (i.e. the *map*) is
* searched against all bpf_local_storage residing at *task*.
*
* An optional *flags* (**BPF_LOCAL_STORAGE_GET_F_CREATE**) can be
* used such that a new bpf_local_storage will be
* created if one does not exist. *value* can be used
* together with **BPF_LOCAL_STORAGE_GET_F_CREATE** to specify
* the initial value of a bpf_local_storage. If *value* is
* **NULL**, the new bpf_local_storage will be zero initialized.
* Return
* A bpf_local_storage pointer is returned on success.
*
* **NULL** if not found or there was an error in adding
* a new bpf_local_storage.
*
* long bpf_task_storage_delete(struct bpf_map *map, struct task_struct *task)
* Description
* Delete a bpf_local_storage from a *task*.
* Return
* 0 on success.
*
* **-ENOENT** if the bpf_local_storage cannot be found.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -3900,6 +3937,8 @@ union bpf_attr {
FN(bpf_per_cpu_ptr), \
FN(bpf_this_cpu_ptr), \
FN(redirect_peer), \
FN(task_storage_get), \
FN(task_storage_delete), \
/* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper