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From: KP Singh <kpsingh@chromium.org>
To: Kees Cook <keescook@chromium.org>
Cc: linux-kernel@vger.kernel.org, bpf@vger.kernel.org,
	linux-security-module@vger.kernel.org,
	Brendan Jackman <jackmanb@google.com>,
	Florent Revest <revest@google.com>, Yonghong Song <yhs@fb.com>,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	James Morris <jmorris@namei.org>, Paul Turner <pjt@google.com>,
	Jann Horn <jannh@google.com>,
	Florent Revest <revest@chromium.org>,
	Brendan Jackman <jackmanb@chromium.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Subject: Re: [PATCH bpf-next v6 3/8] bpf: lsm: provide attachment points for BPF LSM programs
Date: Wed, 25 Mar 2020 21:14:56 +0100	[thread overview]
Message-ID: <20200325201456.GA30568@chromium.org> (raw)
In-Reply-To: <202003251257.AD4381C861@keescook>

On 25-Mär 13:07, Kees Cook wrote:
> On Wed, Mar 25, 2020 at 08:39:56PM +0100, KP Singh wrote:
> > On 25-Mär 12:28, Kees Cook wrote:
> > > On Wed, Mar 25, 2020 at 04:26:24PM +0100, KP Singh wrote:
> > > > +noinline __weak RET bpf_lsm_##NAME(__VA_ARGS__)	\
> > > 
> > > I don't think the __weak is needed any more here?
> > 
> > This was suggested in:
> > 
> >  https://lore.kernel.org/bpf/20200221022537.wbmhdfkdbfvw2pww@ast-mbp/
> > 
> > "I think I saw cases when gcc ignored 'noinline' when function is
> > defined in the same file and still performed inlining while keeping
> > the function body.  To be safe I think __weak is necessary. That will
> > guarantee noinline."
> > 
> > It happened to work nicely with the previous approach for the special
> > hooks but the actual reason for adding the __weak was to guarrantee
> > that these functions don't get inlined.
> 
> Oh, hrm. Well, okay. That rationale would imply that the "noinline"
> macro needs adjustment instead, but that can be separate, something like:
> 
> include/linux/compiler_attributes.h
> 
> -#define noinline __attribute__((__noinline__))
> +#define noinline __attribute__((__noinline__)) __attribute__((__weak__))
> 
> With a comment, etc...

Sounds reasonable, I will drop the __weak from this and send a
separate patch for this.

- KP

> 
> -Kees
> 
> > 
> > > 
> > > > +{						\
> > > > +	return DEFAULT;				\
> > > 
> > > I'm impressed that LSM_RET_VOID actually works. :)
> > 
> > All the credit goes to Andrii :)
> > 
> > - KP
> > 
> > > 
> > > -Kees
> > > 
> > > > +}
> > > > +
> > > > +#include <linux/lsm_hook_defs.h>
> > > > +#undef LSM_HOOK
> > > >  
> > > >  const struct bpf_prog_ops lsm_prog_ops = {
> > > >  };
> > > > -- 
> > > > 2.20.1
> > > > 
> > > 
> > > -- 
> > > Kees Cook
> 
> -- 
> Kees Cook

  reply	other threads:[~2020-03-25 20:15 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-25 15:26 [PATCH bpf-next v6 0/8] MAC and Audit policy using eBPF (KRSI) KP Singh
2020-03-25 15:26 ` [PATCH bpf-next v6 1/8] bpf: Introduce BPF_PROG_TYPE_LSM KP Singh
2020-03-26  1:51   ` Andrii Nakryiko
2020-03-26 13:11     ` KP Singh
2020-03-25 15:26 ` [PATCH bpf-next v6 2/8] security: Refactor declaration of LSM hooks KP Singh
2020-03-25 22:25   ` Casey Schaufler
2020-03-25 23:46     ` KP Singh
2020-03-25 15:26 ` [PATCH bpf-next v6 3/8] bpf: lsm: provide attachment points for BPF LSM programs KP Singh
2020-03-25 19:28   ` Kees Cook
2020-03-25 19:39     ` KP Singh
2020-03-25 20:07       ` Kees Cook
2020-03-25 20:14         ` KP Singh [this message]
2020-03-25 15:26 ` [PATCH bpf-next v6 4/8] bpf: lsm: Implement attach, detach and execution KP Singh
2020-03-26  1:49   ` Andrii Nakryiko
2020-03-26 13:35     ` KP Singh
2020-03-25 15:26 ` [PATCH bpf-next v6 5/8] bpf: lsm: Initialize the BPF LSM hooks KP Singh
2020-03-25 19:30   ` Kees Cook
2020-03-25 15:26 ` [PATCH bpf-next v6 6/8] tools/libbpf: Add support for BPF_PROG_TYPE_LSM KP Singh
2020-03-26  1:56   ` Andrii Nakryiko
2020-03-25 15:26 ` [PATCH bpf-next v6 7/8] bpf: lsm: Add selftests " KP Singh
2020-03-26  2:01   ` Andrii Nakryiko
2020-03-26 13:36     ` KP Singh
2020-03-25 15:26 ` [PATCH bpf-next v6 8/8] bpf: lsm: Add Documentation KP Singh
2020-03-25 19:24 ` [PATCH bpf-next v6 0/8] MAC and Audit policy using eBPF (KRSI) Kees Cook
2020-03-25 19:42   ` KP Singh

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