[bpf-next,1/2] bpf: Add bpf_task_from_vpid() kfunc

Commit Message

Juntong Deng Oct. 14, 2024, 9:21 a.m. UTC

bpf_task_from_pid() that currently exists looks up the
struct task_struct corresponding to the pid in the root pid
namespace (init_pid_ns).

This patch adds bpf_task_from_vpid() which looks up the
struct task_struct corresponding to vpid in the pid namespace
of the current process.

This is useful for getting information about other processes
in the same pid namespace.

Signed-off-by: Juntong Deng <[e-mail]>
---
 kernel/bpf/helpers.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

Comments

[e-mail] Oct. 15, 2024, 2 a.m. UTC | #1

Hello:

This series was applied to bpf/bpf-next.git (master)
by Alexei Starovoitov <[e-mail]>:

On Mon, 14 Oct 2024 10:21:08 +0100 you wrote:
> bpf_task_from_pid() that currently exists looks up the
> struct task_struct corresponding to the pid in the root pid
> namespace (init_pid_ns).
> 
> This patch adds bpf_task_from_vpid() which looks up the
> struct task_struct corresponding to vpid in the pid namespace
> of the current process.
> 
> [...]

Here is the summary with links:
  - [bpf-next,1/2] bpf: Add bpf_task_from_vpid() kfunc
    https://git.kernel.org/bpf/bpf-next/c/6dce087f24e5
  - [bpf-next,2/2] selftests/bpf: Add tests for bpf_task_from_vpid() kfunc
    https://git.kernel.org/bpf/bpf-next/c/108e7b4db83b

You are awesome, thank you!

Patch

diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 4053f279ed4c..e977c12d60e1 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -2521,6 +2521,25 @@  __bpf_kfunc struct task_struct *bpf_task_from_pid(s32 pid)
 	return p;
 }
 
+/**
+ * bpf_task_from_vpid - Find a struct task_struct from its vpid by looking it up
+ * in the pid namespace of the current task. If a task is returned, it must
+ * either be stored in a map, or released with bpf_task_release().
+ * @vpid: The vpid of the task being looked up.
+ */
+__bpf_kfunc struct task_struct *bpf_task_from_vpid(s32 vpid)
+{
+	struct task_struct *p;
+
+	rcu_read_lock();
+	p = find_task_by_vpid(vpid);
+	if (p)
+		p = bpf_task_acquire(p);
+	rcu_read_unlock();
+
+	return p;
+}
+
 /**
  * bpf_dynptr_slice() - Obtain a read-only pointer to the dynptr data.
  * @p: The dynptr whose data slice to retrieve
@@ -3034,6 +3053,7 @@  BTF_ID_FLAGS(func, bpf_task_under_cgroup, KF_RCU)
 BTF_ID_FLAGS(func, bpf_task_get_cgroup1, KF_ACQUIRE | KF_RCU | KF_RET_NULL)
 #endif
 BTF_ID_FLAGS(func, bpf_task_from_pid, KF_ACQUIRE | KF_RET_NULL)
+BTF_ID_FLAGS(func, bpf_task_from_vpid, KF_ACQUIRE | KF_RET_NULL)
 BTF_ID_FLAGS(func, bpf_throw)
 BTF_KFUNCS_END(generic_btf_ids)