From 3f0e6f2b41d35d4446160c745e8f09037447dd8f Mon Sep 17 00:00:00 2001 From: David Vernet Date: Tue, 22 Nov 2022 08:52:59 -0600 Subject: [PATCH] bpf: Add bpf_task_from_pid() kfunc Callers can currently store tasks as kptrs using bpf_task_acquire(), bpf_task_kptr_get(), and bpf_task_release(). These are useful if a caller already has a struct task_struct *, but there may be some callers who only have a pid, and want to look up the associated struct task_struct * from that to e.g. find task->comm. This patch therefore adds a new bpf_task_from_pid() kfunc which allows BPF programs to get a struct task_struct * kptr from a pid. Signed-off-by: David Vernet Link: https://lore.kernel.org/r/20221122145300.251210-2-void@manifault.com Signed-off-by: Alexei Starovoitov --- kernel/bpf/helpers.c | 21 ++++++++++++++++++++- 1 file changed, 20 insertions(+), 1 deletion(-) diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index da2681e..2299bb0 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -1959,6 +1959,25 @@ struct cgroup *bpf_cgroup_ancestor(struct cgroup *cgrp, int level) } #endif /* CONFIG_CGROUPS */ +/** + * bpf_task_from_pid - Find a struct task_struct from its pid by looking it up + * in the root pid namespace idr. If a task is returned, it must either be + * stored in a map, or released with bpf_task_release(). + * @pid: The pid of the task being looked up. + */ +struct task_struct *bpf_task_from_pid(s32 pid) +{ + struct task_struct *p; + + rcu_read_lock(); + p = find_task_by_pid_ns(pid, &init_pid_ns); + if (p) + bpf_task_acquire(p); + rcu_read_unlock(); + + return p; +} + void *bpf_cast_to_kern_ctx(void *obj) { return obj; @@ -1984,13 +2003,13 @@ BTF_ID_FLAGS(func, bpf_list_pop_back, KF_ACQUIRE | KF_RET_NULL) BTF_ID_FLAGS(func, bpf_task_acquire, KF_ACQUIRE | KF_TRUSTED_ARGS) BTF_ID_FLAGS(func, bpf_task_kptr_get, KF_ACQUIRE | KF_KPTR_GET | KF_RET_NULL) BTF_ID_FLAGS(func, bpf_task_release, KF_RELEASE) - #ifdef CONFIG_CGROUPS BTF_ID_FLAGS(func, bpf_cgroup_acquire, KF_ACQUIRE | KF_TRUSTED_ARGS) BTF_ID_FLAGS(func, bpf_cgroup_kptr_get, KF_ACQUIRE | KF_KPTR_GET | KF_RET_NULL) BTF_ID_FLAGS(func, bpf_cgroup_release, KF_RELEASE) BTF_ID_FLAGS(func, bpf_cgroup_ancestor, KF_ACQUIRE | KF_TRUSTED_ARGS | KF_RET_NULL) #endif +BTF_ID_FLAGS(func, bpf_task_from_pid, KF_ACQUIRE | KF_RET_NULL) BTF_SET8_END(generic_btf_ids) static const struct btf_kfunc_id_set generic_kfunc_set = { -- 2.7.4