From a10787e6d58c24b51e91c19c6d16c5da89fcaa4b Mon Sep 17 00:00:00 2001 From: Song Liu Date: Thu, 25 Feb 2021 15:43:14 -0800 Subject: bpf: Enable task local storage for tracing programs 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). Signed-off-by: Song Liu Signed-off-by: Alexei Starovoitov Acked-by: KP Singh Acked-by: Martin KaFai Lau Link: https://lore.kernel.org/bpf/20210225234319.336131-2-songliubraving@fb.com --- include/linux/bpf.h | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'include/linux/bpf.h') diff --git a/include/linux/bpf.h b/include/linux/bpf.h index cccaef1088ea..e2cfc4809219 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); -- cgit v1.2.3-70-g09d2