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From: Gabriele <phoenix1987@gmail.com>
To: Andrii Nakryiko <andrii@kernel.org>
Cc: Kenny Yu <kennyyu@fb.com>,
	Alexei Starovoitov <alexei.starovoitov@gmail.com>,
	Alexei Starovoitov <ast@kernel.org>, bpf <bpf@vger.kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Yonghong Song <yhs@fb.com>
Subject: Re: [PATCH v2 bpf-next 4/4] selftests/bpf: Add test for sleepable bpf iterator programs
Date: Sat, 15 Jan 2022 16:27:10 +0000	[thread overview]
Message-ID: <CAGnuNNv0TVQ3ZSYjJgJh1Dxasc9pX-QTwVApYyW7Q0xEy0Bgng@mail.gmail.com> (raw)
In-Reply-To: <CAEf4BzY9s1ngF_ja_rrpY=1cNX=byVSjptNT-LaEKTsUJEfP6Q@mail.gmail.com>

On Sat, 15 Jan 2022 at 15:48, Andrii Nakryiko <andrii.nakryiko@gmail.com> wrote:
>
> On Fri, Jan 14, 2022 at 3:14 PM Kenny Yu <kennyyu@fb.com> wrote:
> >
> > Hi Alexei,
> >
> > > > +// New helper added
> > > > +static long (*bpf_access_process_vm)(
> > > > +       struct task_struct *tsk,
> > > > +       unsigned long addr,
> > > > +       void *buf,
> > > > +       int len,
> > > > +       unsigned int gup_flags) = (void *)186;
> > >
> > > This shouldn't be needed.
> > > Since patch 1 updates tools/include/uapi/linux/bpf.h
> > > it will be in bpf_helper_defs.h automatically.
> >
> > I will fix. This is my first time writing selftests, so I am not too familiar
> > with how these are built and run. For my understanding, are these tests
> > meant to be built and run after booting the new kernel?
>
> Look at vmtest.sh under tools/testing/selftests/bpf, it handles
> building kernel, selftests and spinning up qemu instance for running
> selftests inside it.
>
> >
> > > > +
> > > > +// Copied from include/linux/mm.h
> > > > +#define FOLL_REMOTE 0x2000 /* we are working on non-current tsk/mm */
> > >
> > > Please use C style comments only.
> >
> > I will fix.
> >
> > > > +       numread = bpf_access_process_vm(task,
> > > > +                                       (unsigned long)ptr,
> > > > +                                       (void *)&user_data,
> > > > +                                       sizeof(uint32_t),
> > > > +                                       FOLL_REMOTE);
> > >
> > > We probably would need to hide flags like FOLL_REMOTE
> > > inside the helper otherwise prog might confuse the kernel.
> > > In this case I'm not even sure that FOLL_REMOTE is needed.
> > > I suspect gup_flags=0 in all cases will work fine.
> > > We're not doing write here and not pining anything.
> > > fast_gup is not necessary either.
> >
> > Thanks for the suggestion! I'll remove the flag argument from the helper
> > to simplify the API for bpf programs. This means that the helper will have
> > the following signature:
> >
> >   bpf_access_process_vm(struct task_struct *tsk,
> >                         unsigned long addr,
> >                         void *buf,
> >                         int len);
>
> keeping generic u64 flags makes sense for the future, so I'd keep it.
>
> But I also wanted to point out that this helper is logically in the
> same family as bpf_probe_read_kernel/user and bpf_copy_from_user, etc,
> where we have consistent pattern that first two arguments specify
> destination buffer (so buf + len) and the remaining ones specify
> source (in probe_read it's just an address, here it's tsk_addr). So I
> wonder if it would be less surprising and more consistent to reorder
> and have:
>
> buf, len, tsk, addr, flags
>
> ?
>

I would personally find it more intuitive to have process information
passed as either the first argument (like process_vm_readv does), or
as "last", just before the flags (as extra information required w.r.t.
to local versions, e.g. bpf_copy_from_user).

  parent reply	other threads:[~2022-01-15 16:27 UTC|newest]

Thread overview: 62+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-01-13 23:31 [PATCH bpf-next 0/3] Add bpf_access_process_vm helper and sleepable bpf iterator programs Kenny Yu
2022-01-13 23:31 ` [PATCH bpf-next 1/3] bpf: Add bpf_access_process_vm() helper Kenny Yu
2022-01-13 23:31 ` [PATCH bpf-next 2/3] libbpf: Add "iter.s" section for sleepable bpf iterator programs Kenny Yu
2022-01-13 23:31 ` [PATCH bpf-next 3/3] selftests/bpf: Add test " Kenny Yu
2022-01-14  0:48 ` [PATCH v2 bpf-next 0/4] Add bpf_access_process_vm helper and " Kenny Yu
2022-01-14  0:48   ` [PATCH v2 bpf-next 1/4] bpf: Add bpf_access_process_vm() helper Kenny Yu
2022-01-14  0:48   ` [PATCH v2 bpf-next 2/4] bpf: Add support for sleepable programs in bpf_iter_run_prog Kenny Yu
2022-01-14  2:50     ` Alexei Starovoitov
2022-01-14 23:15       ` Kenny Yu
2022-01-14  0:48   ` [PATCH v2 bpf-next 3/4] libbpf: Add "iter.s" section for sleepable bpf iterator programs Kenny Yu
2022-01-14  0:49   ` [PATCH v2 bpf-next 4/4] selftests/bpf: Add test " Kenny Yu
2022-01-14  2:39     ` Alexei Starovoitov
2022-01-14 23:14       ` Kenny Yu
2022-01-15  1:38         ` Andrii Nakryiko
2022-01-15  4:30           ` Kenny Yu
2022-01-15 16:27           ` Gabriele [this message]
2022-01-19 16:56             ` Kenny Yu
2022-01-19 18:02 ` [PATCH v3 bpf-next 0/3] Add bpf_access_process_vm helper and " Kenny Yu
2022-01-19 18:02   ` [PATCH v3 bpf-next 1/3] bpf: Add bpf_access_process_vm() helper Kenny Yu
2022-01-19 20:16     ` Alexei Starovoitov
2022-01-19 22:51       ` Kenny Yu
2022-01-19 18:02   ` [PATCH v3 bpf-next 2/3] libbpf: Add "iter.s" section for sleepable bpf iterator programs Kenny Yu
2022-01-19 18:02   ` [PATCH v3 bpf-next 3/3] selftests/bpf: Add test " Kenny Yu
2022-01-19 22:59 ` [PATCH v4 bpf-next 0/3] Add bpf_access_process_vm helper and " Kenny Yu
2022-01-19 22:59   ` [PATCH v4 bpf-next 1/3] bpf: Add bpf_access_process_vm() helper Kenny Yu
2022-01-20  3:45     ` Yonghong Song
2022-01-20 17:11       ` Kenny Yu
2022-01-19 22:59   ` [PATCH v4 bpf-next 2/3] libbpf: Add "iter.s" section for sleepable bpf iterator programs Kenny Yu
2022-01-19 22:59   ` [PATCH v4 bpf-next 3/3] selftests/bpf: Add test " Kenny Yu
2022-01-20 17:29 ` [PATCH v5 bpf-next 0/3] Add bpf_access_process_vm helper and " Kenny Yu
2022-01-20 17:29   ` [PATCH v5 bpf-next 1/3] bpf: Add bpf_access_process_vm() helper Kenny Yu
2022-01-20 22:45     ` Andrii Nakryiko
2022-01-21  2:27       ` Alexei Starovoitov
2022-01-21 17:20         ` Andrii Nakryiko
2022-01-21 17:41           ` Kenny Yu
2022-01-21 17:47             ` Alexei Starovoitov
2022-01-21 18:30               ` Kenny Yu
2022-01-20 17:29   ` [PATCH v5 bpf-next 2/3] libbpf: Add "iter.s" section for sleepable bpf iterator programs Kenny Yu
2022-01-20 17:29   ` [PATCH v5 bpf-next 3/3] selftests/bpf: Add test " Kenny Yu
2022-01-20 22:48     ` Andrii Nakryiko
2022-01-21 19:30 ` [PATCH v6 bpf-next 0/3] Add bpf_copy_from_user_task helper and " Kenny Yu
2022-01-21 19:30   ` [PATCH v6 bpf-next 1/3] bpf: Add bpf_copy_from_user_task() helper Kenny Yu
2022-01-21 19:53     ` Andrii Nakryiko
2022-01-21 20:04       ` Yonghong Song
2022-01-21 20:07         ` Andrii Nakryiko
2022-01-21 21:15           ` Yonghong Song
2022-01-24 17:30             ` Kenny Yu
2022-01-22  9:58       ` Gabriele
2022-01-22 10:08         ` Gabriele
2022-01-21 19:30   ` [PATCH v6 bpf-next 2/3] libbpf: Add "iter.s" section for sleepable bpf iterator programs Kenny Yu
2022-01-21 19:54     ` Andrii Nakryiko
2022-01-21 19:30   ` [PATCH v6 bpf-next 3/3] selftests/bpf: Add test " Kenny Yu
2022-01-21 19:55     ` Andrii Nakryiko
2022-01-24 18:53 ` [PATCH v7 bpf-next 0/4] Add bpf_copy_from_user_task helper and " Kenny Yu
2022-01-24 18:54   ` [PATCH v7 bpf-next 1/4] bpf: Add support for bpf iterator programs to use sleepable helpers Kenny Yu
2022-01-24 22:19     ` Andrii Nakryiko
2022-01-24 18:54   ` [PATCH v7 bpf-next 2/4] bpf: Add bpf_copy_from_user_task() helper Kenny Yu
2022-01-24 22:18     ` Andrii Nakryiko
2022-01-25  4:06       ` Alexei Starovoitov
2022-01-24 18:54   ` [PATCH v7 bpf-next 3/4] libbpf: Add "iter.s" section for sleepable bpf iterator programs Kenny Yu
2022-01-24 18:54   ` [PATCH v7 bpf-next 4/4] selftests/bpf: Add test " Kenny Yu
2022-01-25  4:10   ` [PATCH v7 bpf-next 0/4] Add bpf_copy_from_user_task helper and " patchwork-bot+netdevbpf

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