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From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: Yonghong Song <yhs@fb.com>
Cc: davem@davemloft.net, daniel@iogearbox.net, andrii@kernel.org,
	netdev@vger.kernel.org, bpf@vger.kernel.org, kernel-team@fb.com
Subject: Re: [PATCH v2 bpf-next 00/16] bpf: syscall program, FD array, loader program, light skeleton.
Date: Fri, 23 Apr 2021 16:16:42 -0700	[thread overview]
Message-ID: <20210423231642.tbypsaxqurjnjqts@ast-mbp.dhcp.thefacebook.com> (raw)
In-Reply-To: <4142514b-3a0f-f931-9a8c-fb72be9c66b3@fb.com>

On Fri, Apr 23, 2021 at 02:36:43PM -0700, Yonghong Song wrote:
> > 
> > One thing that was not addressed from feedback is the name of new program type.
> > Currently it's still:
> > BPF_PROG_TYPE_SYSCALL, /* a program that can execute syscalls */
> 
> Do you have plan for other non-bpf syscalls? Maybe use the name
> BPF_PROG_TYPE_BPF_SYSCALL? It will be really clear this is
> the program type you can execute bpf syscalls.

In this patch set it's already doing sys_bpf and sys_close syscalls :)

> > 
> > The concern raised was that it sounds like a program that should be attached
> > to a syscall. Like BPF_PROG_TYPE_KPROBE is used to process kprobes.
> > I've considered and rejected:
> > BPF_PROG_TYPE_USER - too generic
> > BPF_PROG_TYPE_USERCTX - ambiguous with uprobes
> 
> USERCTX probably not a good choice. People can write a program without
> context and put the ctx into a map and use it.
> 
> > BPF_PROG_TYPE_LOADER - ok-ish, but imo TYPE_SYSCALL is cleaner.
> 
> User can write a program to do more than loading although I am not sure
> how useful it is compared to implementation in user space.

Exactly.
Just BPF_PROG_TYPE_SYSCALL alone can be used as more generic equivalent
to sys_close_range syscalls.
If somebody needs to close a sparse set of FDs or get fd_to_be_closed
from a map they can craft a bpf prog that would do that.
Or if somebody wants to do a batched map processing...
instead of doing sys_bpf() with BPF_MAP_UPDATE_BATCH they can craft
a bpf prog.
Plenty of use cases beyond LOADER.

This patch set only allows BPF_PROG_TYPE_SYSCALL to be executed
via prog_test_run, but I think it's safe to execute it upon entry
to pretty much any syscall.
So _SYSCALL suffix fits as both "a program that can execute syscalls"
and as "a program that attaches to syscalls".
The later is not implemented yet, but would fit right in.

      reply	other threads:[~2021-04-23 23:16 UTC|newest]

Thread overview: 52+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-23  0:26 [PATCH v2 bpf-next 00/16] bpf: syscall program, FD array, loader program, light skeleton Alexei Starovoitov
2021-04-23  0:26 ` [PATCH v2 bpf-next 01/16] bpf: Introduce bpf_sys_bpf() helper and program type Alexei Starovoitov
2021-04-23 18:15   ` Yonghong Song
2021-04-23 18:28     ` Alexei Starovoitov
2021-04-23 19:32       ` Yonghong Song
2021-04-26 16:51   ` Andrii Nakryiko
2021-04-27 18:45   ` John Fastabend
2021-04-23  0:26 ` [PATCH v2 bpf-next 02/16] bpf: Introduce bpfptr_t user/kernel pointer Alexei Starovoitov
2021-04-23  0:26 ` [PATCH v2 bpf-next 03/16] bpf: Prepare bpf syscall to be used from kernel and user space Alexei Starovoitov
2021-04-23  0:26 ` [PATCH v2 bpf-next 04/16] libbpf: Support for syscall program type Alexei Starovoitov
2021-04-26 22:24   ` Andrii Nakryiko
2021-04-23  0:26 ` [PATCH v2 bpf-next 05/16] selftests/bpf: Test " Alexei Starovoitov
2021-04-26 17:02   ` Andrii Nakryiko
2021-04-27  2:43     ` Alexei Starovoitov
2021-04-27 16:28       ` Andrii Nakryiko
2021-04-23  0:26 ` [PATCH v2 bpf-next 06/16] bpf: Make btf_load command to be bpfptr_t compatible Alexei Starovoitov
2021-04-23  0:26 ` [PATCH v2 bpf-next 07/16] selftests/bpf: Test for btf_load command Alexei Starovoitov
2021-04-23  0:26 ` [PATCH v2 bpf-next 08/16] bpf: Introduce fd_idx Alexei Starovoitov
2021-04-23  0:26 ` [PATCH v2 bpf-next 09/16] libbpf: Support for fd_idx Alexei Starovoitov
2021-04-26 17:14   ` Andrii Nakryiko
2021-04-27  2:53     ` Alexei Starovoitov
2021-04-27 16:36       ` Andrii Nakryiko
2021-04-28  1:32         ` Alexei Starovoitov
2021-04-28 18:40           ` Andrii Nakryiko
2021-04-23  0:26 ` [PATCH v2 bpf-next 10/16] bpf: Add bpf_btf_find_by_name_kind() helper Alexei Starovoitov
2021-04-26 22:46   ` Andrii Nakryiko
2021-04-27  3:37     ` Alexei Starovoitov
2021-04-27 17:45       ` Andrii Nakryiko
2021-04-28  1:55         ` Alexei Starovoitov
2021-04-28 18:44           ` Andrii Nakryiko
2021-04-27 21:00   ` John Fastabend
2021-04-27 21:05     ` John Fastabend
2021-04-28  2:10     ` Alexei Starovoitov
2021-04-23  0:26 ` [PATCH v2 bpf-next 11/16] bpf: Add bpf_sys_close() helper Alexei Starovoitov
2021-04-23  0:26 ` [PATCH v2 bpf-next 12/16] libbpf: Change the order of data and text relocations Alexei Starovoitov
2021-04-26 17:29   ` Andrii Nakryiko
2021-04-27  3:00     ` Alexei Starovoitov
2021-04-27 16:47       ` Andrii Nakryiko
2021-04-23  0:26 ` [PATCH v2 bpf-next 13/16] libbpf: Add bpf_object pointer to kernel_supports() Alexei Starovoitov
2021-04-26 17:30   ` Andrii Nakryiko
2021-04-23  0:26 ` [PATCH v2 bpf-next 14/16] libbpf: Generate loader program out of BPF ELF file Alexei Starovoitov
2021-04-26 22:22   ` Andrii Nakryiko
2021-04-27  3:25     ` Alexei Starovoitov
2021-04-27 17:34       ` Andrii Nakryiko
2021-04-28  1:42         ` Alexei Starovoitov
2021-04-23  0:26 ` [PATCH v2 bpf-next 15/16] bpftool: Use syscall/loader program in "prog load" and "gen skeleton" command Alexei Starovoitov
2021-04-26 22:35   ` Andrii Nakryiko
2021-04-27  3:28     ` Alexei Starovoitov
2021-04-27 17:38       ` Andrii Nakryiko
2021-04-23  0:26 ` [PATCH v2 bpf-next 16/16] selftests/bpf: Convert few tests to light skeleton Alexei Starovoitov
2021-04-23 21:36 ` [PATCH v2 bpf-next 00/16] bpf: syscall program, FD array, loader program, " Yonghong Song
2021-04-23 23:16   ` Alexei Starovoitov [this message]

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