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 --- kernel/fork.c | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'kernel/fork.c') diff --git a/kernel/fork.c b/kernel/fork.c index d66cd1014211..181604db2d65 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -96,6 +96,7 @@ #include #include #include +#include #include #include @@ -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); -- cgit