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| author | Song Liu <songliubraving@fb.com> | 2021-02-26 00:43:14 +0100 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2021-02-26 20:51:47 +0100 |
| commit | a10787e6d58c24b51e91c19c6d16c5da89fcaa4b (patch) | |
| tree | 115e4d7d43d1353084fc3b9e54935aad16c6f821 /kernel/fork.c | |
| parent | xsk: Build skb by page (aka generic zerocopy xmit) (diff) | |
| download | linux-a10787e6d58c24b51e91c19c6d16c5da89fcaa4b.tar.xz linux-a10787e6d58c24b51e91c19c6d16c5da89fcaa4b.zip | |
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 <songliubraving@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: KP Singh <kpsingh@kernel.org>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20210225234319.336131-2-songliubraving@fb.com
Diffstat (limited to 'kernel/fork.c')
| -rw-r--r-- | kernel/fork.c | 5 |
1 files changed, 5 insertions, 0 deletions
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 <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); |