From: Alexei Starovoitov <ast@plumgrid.com>
To: Andy Lutomirski <luto@amacapital.net>
Cc: "David S. Miller" <davem@davemloft.net>,
Ingo Molnar <mingo@kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
Wang Nan <wangnan0@huawei.com>, Li Zefan <lizefan@huawei.com>,
Daniel Wagner <daniel.wagner@bmw-carit.de>,
Daniel Borkmann <daniel@iogearbox.net>,
Linux API <linux-api@vger.kernel.org>,
Network Development <netdev@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH net-next 1/3] bpf: introduce current->pid, tgid, uid, gid, comm accessors
Date: Fri, 12 Jun 2015 15:44:43 -0700 [thread overview]
Message-ID: <557B60DB.5030200@plumgrid.com> (raw)
In-Reply-To: <CALCETrUidQ9ig-xZrAFX8_==aVbDNKU-GfeYNMsT6uHugqSydg@mail.gmail.com>
On 6/12/15 3:08 PM, Andy Lutomirski wrote:
> On Fri, Jun 12, 2015 at 2:40 PM, Alexei Starovoitov <ast@plumgrid.com> wrote:
>> eBPF programs attached to kprobes need to filter based on
>> current->pid, uid and other fields, so introduce helper functions:
>>
>> u64 bpf_get_current_pid_tgid(void)
>> Return: current->tgid << 32 | current->pid
>>
>> u64 bpf_get_current_uid_gid(void)
>> Return: current_gid << 32 | current_uid
>
> How does this work wrt namespaces,
from_kuid(current_user_ns(), uid)
> and why the weird packing?
to minimize number of calls.
We've considered several alternatives.
1. 5 different helpers
Cons: every call adds performance overhead
2a: single helper that populates 'struct bpf_task_info'
and uses 'flags' with bit per field.
+struct bpf_task_info {
+ __u32 pid;
+ __u32 tgid;
+ __u32 uid;
+ __u32 gid;
+ char comm[16];
+};
bpf_get_current_task_info(task_info, size, flags)
bit 0 - fill in pid
bit 1 - fill in tgid
Pros: single helper
Cons: ugly to use and a lot of compares in the helper
itself (two compares for each field)
2b. single helper that populates 'struct bpf_task_info'
and uses 'size' to tell how many fields to fill in.
bpf_get_current_task_info(task_info, size);
+ if (size >= offsetof(struct bpf_task_info, pid) + sizeof(info->pid))
+ info->pid = task->pid;
+ if (size >= offsetof(struct bpf_task_info, tgid) +
sizeof(info->tgid))
+ info->tgid = task->tgid;
Pros: single call (with single compare per field).
Cons: still hard to use when only uid is needed.
These three helpers looked as the best balance between
performance and usability.
next prev parent reply other threads:[~2015-06-12 22:44 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-12 21:40 [PATCH net-next 0/3] bpf: share helpers between tracing and networking Alexei Starovoitov
2015-06-12 21:40 ` Alexei Starovoitov
2015-06-12 21:40 ` [PATCH net-next 1/3] bpf: introduce current->pid, tgid, uid, gid, comm accessors Alexei Starovoitov
2015-06-12 21:40 ` Alexei Starovoitov
2015-06-12 22:08 ` Andy Lutomirski
2015-06-12 22:08 ` Andy Lutomirski
2015-06-12 22:44 ` Alexei Starovoitov [this message]
2015-06-12 22:54 ` Andy Lutomirski
2015-06-12 23:23 ` Alexei Starovoitov
2015-06-12 23:25 ` Andy Lutomirski
2015-06-12 23:38 ` Alexei Starovoitov
2015-06-12 23:47 ` Andy Lutomirski
2015-06-12 23:55 ` Alexei Starovoitov
2015-06-13 0:03 ` Andy Lutomirski
2015-06-13 0:15 ` Alexei Starovoitov
2015-06-13 0:15 ` Alexei Starovoitov
2015-06-13 0:24 ` Andy Lutomirski
2015-06-13 0:26 ` Alexei Starovoitov
2015-06-13 0:26 ` Alexei Starovoitov
2015-06-12 21:40 ` [PATCH net-next 2/3] bpf: allow networking programs to use bpf_trace_printk() for debugging Alexei Starovoitov
2015-06-12 21:40 ` Alexei Starovoitov
2015-06-12 21:40 ` [PATCH net-next 3/3] bpf: let kprobe programs use bpf_get_smp_processor_id() helper Alexei Starovoitov
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=557B60DB.5030200@plumgrid.com \
--to=ast@plumgrid.com \
--cc=daniel.wagner@bmw-carit.de \
--cc=daniel@iogearbox.net \
--cc=davem@davemloft.net \
--cc=linux-api@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=lizefan@huawei.com \
--cc=luto@amacapital.net \
--cc=mingo@kernel.org \
--cc=netdev@vger.kernel.org \
--cc=rostedt@goodmis.org \
--cc=wangnan0@huawei.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.