linux-kernel - Re: [PATCH 1/2] entry: Fix CONFIG

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Message-ID: <20200726174731.GA786388@gmail.com>
Date:   Sun, 26 Jul 2020 19:47:31 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Borislav Petkov <bp@...en8.de>
Subject: Re: [PATCH 1/2] entry: Fix CONFIG_SECCOMP assumption


* Thomas Gleixner <tglx@...utronix.de> wrote:

> Ingo Molnar <mingo@...nel.org> writes:
> > The __secure_computing() callback only exists on CONFIG_SECCOMP=y,
> 
> No. There is a stub function for the SECCOMP=n case.

Which was buggy:

  static inline int __secure_computing(void) { return 0; }

Note the 'void' argument, while it should take an argument.

For example on x86-64 allnoconfig there's !CONFIG_SECCOMP.

> > and on architectures that have CONFIG_HAVE_ARCH_SECCOMP_FILTER.
> 
> which is a prerequiste for converting over.

Yeah, and the patch I sent makes this explicit instead of implicit.

> > Instead of complicating the #ifdef within the generic entry code,
> 
> There is no #ifdef in the generic code and there is none required.

I simply carried that #ifdef over from the x86 code, but indeed fixing 
the stub is a bit cleaner.

> > make the generic entry code depend on the availability of a modern
> > seccomp framework. This was implicit in the generic code due to
> > x86 being a modern seccomp-filter architecture.
> >
> > Also move the Kconfig entry to after its HAVE_ARCH_SECCOMP_FILTER
> > dependency and fix minor whitespace damage while at it.
> >
> > Fixes: 142781e108b1: ("entry: Provide generic syscall entry
> > functionality")
> 
> I don't see what that fixes.

A build bug.

Thanks,

	Ingo