linux-kernel - Re: [PATCH v9 01/10] btf: Add a new kfunc flag which allows to mark a function to be sleepable

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Message-ID: <e807779b-e72b-e197-b833-43373e87d3df@iogearbox.net>
Date:   Wed, 10 Aug 2022 16:38:54 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        Roberto Sassu <roberto.sassu@...wei.com>
Cc:     Jarkko Sakkinen <jarkko@...nel.org>,
        "ast@...nel.org" <ast@...nel.org>,
        "andrii@...nel.org" <andrii@...nel.org>,
        "martin.lau@...ux.dev" <martin.lau@...ux.dev>,
        "song@...nel.org" <song@...nel.org>, "yhs@...com" <yhs@...com>,
        "john.fastabend@...il.com" <john.fastabend@...il.com>,
        "kpsingh@...nel.org" <kpsingh@...nel.org>,
        "sdf@...gle.com" <sdf@...gle.com>,
        "haoluo@...gle.com" <haoluo@...gle.com>,
        "jolsa@...nel.org" <jolsa@...nel.org>,
        "corbet@....net" <corbet@....net>,
        "dhowells@...hat.com" <dhowells@...hat.com>,
        "rostedt@...dmis.org" <rostedt@...dmis.org>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "paul@...l-moore.com" <paul@...l-moore.com>,
        "jmorris@...ei.org" <jmorris@...ei.org>,
        "serge@...lyn.com" <serge@...lyn.com>,
        "shuah@...nel.org" <shuah@...nel.org>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "keyrings@...r.kernel.org" <keyrings@...r.kernel.org>,
        "linux-security-module@...r.kernel.org" 
        <linux-security-module@...r.kernel.org>,
        "linux-kselftest@...r.kernel.org" <linux-kselftest@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Yosry Ahmed <yosryahmed@...gle.com>
Subject: Re: [PATCH v9 01/10] btf: Add a new kfunc flag which allows to mark a
 function to be sleepable

On 8/10/22 4:25 PM, Benjamin Tissoires wrote:
> On Wed, Aug 10, 2022 at 3:44 PM Roberto Sassu <roberto.sassu@...wei.com> wrote:
>>> From: Jarkko Sakkinen [mailto:jarkko@...nel.org]
>>> Sent: Tuesday, August 9, 2022 6:55 PM
>>> On Tue, Aug 09, 2022 at 03:45:54PM +0200, Roberto Sassu wrote:
>>>> From: Benjamin Tissoires <benjamin.tissoires@...hat.com>
>>>>
>>>> From: Benjamin Tissoires <benjamin.tissoires@...hat.com>
>>>>
>>>> This allows to declare a kfunc as sleepable and prevents its use in
>>>> a non sleepable program.
>>>
>>> Nit: "Declare a kfunc as sleepable and prevent its use in a
>>> non-sleepable program."
>>>
>>> It's missing the part *how* the patch accomplishes its goals.
>>
>> I will add:
>>
>> If an eBPF program is going to call a kfunc declared as sleepable,
>> eBPF will look at the eBPF program flags. If BPF_F_SLEEPABLE is
>> not set, execution of that program is denied.
> 
> All those changes are looking good to me.
> 
> Thanks a lot for keeping pushing on this patch :)

This single one from the series got already applied here:

   https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git/commit/?id=fa96b24204af42274ec13dfb2f2e6990d7510e55

>>>> Signed-off-by: Benjamin Tissoires <benjamin.tissoires@...hat.com>
>>>> Co-developed-by: Yosry Ahmed <yosryahmed@...gle.com>
>>>> Signed-off-by: Yosry Ahmed <yosryahmed@...gle.com>
>>>> Signed-off-by: Hao Luo <haoluo@...gle.com>
>>>> ---
>>>>   Documentation/bpf/kfuncs.rst | 6 ++++++
>>>>   include/linux/btf.h          | 1 +
>>>>   kernel/bpf/btf.c             | 9 +++++++++
>>>>   3 files changed, 16 insertions(+)
>>>>
>>>> diff --git a/Documentation/bpf/kfuncs.rst b/Documentation/bpf/kfuncs.rst
>>>> index c0b7dae6dbf5..c8b21de1c772 100644
>>>> --- a/Documentation/bpf/kfuncs.rst
>>>> +++ b/Documentation/bpf/kfuncs.rst
>>>> @@ -146,6 +146,12 @@ that operate (change some property, perform some
>>> operation) on an object that
>>>>   was obtained using an acquire kfunc. Such kfuncs need an unchanged pointer
>>> to
>>>>   ensure the integrity of the operation being performed on the expected object.