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authorDavid Vernet <void@manifault.com>2022-11-22 08:52:59 -0600
committerAlexei Starovoitov <ast@kernel.org>2022-11-23 17:45:23 -0800
commit3f0e6f2b41d35d4446160c745e8f09037447dd8f (patch)
treeb175c6182c6108a34cfe5d9eda1218fd17cd0151 /kernel
parent5bad3587b7a292148cea10185cd8770baaeb7445 (diff)
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 <void@manifault.com> Link: https://lore.kernel.org/r/20221122145300.251210-2-void@manifault.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/bpf/helpers.c21
1 files changed, 20 insertions, 1 deletions
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index da2681ebb7c3..2299bb0d89e5 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 = {