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From: Peter Zijlstra <peterz@infradead.org>
To: Gabriel Krisman Bertazi <krisman@collabora.com>
Cc: luto@kernel.org, tglx@linutronix.de, keescook@chromium.org,
	x86@kernel.org, linux-kernel@vger.kernel.org,
	linux-api@vger.kernel.org, willy@infradead.org,
	linux-kselftest@vger.kernel.org, shuah@kernel.org,
	kernel@collabora.com
Subject: Re: [PATCH v6 1/9] kernel: Support TIF_SYSCALL_INTERCEPT flag
Date: Thu, 24 Sep 2020 13:24:41 +0200	[thread overview]
Message-ID: <20200924112441.GF2628@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <878sdgnkj6.fsf@collabora.com>

On Fri, Sep 11, 2020 at 04:08:45PM -0400, Gabriel Krisman Bertazi wrote:
> peterz@infradead.org writes:
> 
> > On Fri, Sep 04, 2020 at 04:31:39PM -0400, Gabriel Krisman Bertazi wrote:
> >> +static inline void __set_tsk_syscall_intercept(struct task_struct *tsk,
> >> +					   unsigned int type)
> >> +{
> >> +	tsk->syscall_intercept |= type;
> >> +
> >> +	if (tsk->syscall_intercept)
> >> +		set_tsk_thread_flag(tsk, TIF_SYSCALL_INTERCEPT);
> >> +}
> >
> > Did the above want to be:
> >
> > 	unsigned int old = tsk->syscall_intercept;
> > 	tsk->syscall_intercept |= type;
> > 	if (!old)
> > 		set_tsk_thread_flag(tsk, TIF_SYSCALL_INTERCEPT)
> >
> 
> Hi Peter,
> 
> Thanks for the review!
> 
> I'm not sure this change gains us anything.  For now,
> __set_tsk_syscall_intercept cannot be called with !type, so both
> versions behave the same, but my version is safe with that scenario.
> This won't be called frequent enough for the extra calls to
> set_tsk_thread_flag matter.  Am I missing something?

Your version will do set_tsk_thread_flag() for every invocation
(assuming non-zero type). That's sub-optimal.

  reply	other threads:[~2020-09-24 11:24 UTC|newest]

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-04 20:31 [PATCH v6 0/9] Syscall User Dispatch Gabriel Krisman Bertazi
2020-09-04 20:31 ` [PATCH v6 1/9] kernel: Support TIF_SYSCALL_INTERCEPT flag Gabriel Krisman Bertazi
2020-09-07 10:16   ` Christian Brauner
2020-09-08  4:59     ` Gabriel Krisman Bertazi
2020-09-22 19:42       ` Kees Cook
2020-09-23 20:28         ` Gabriel Krisman Bertazi
2020-09-11  9:32   ` peterz
2020-09-11 20:08     ` Gabriel Krisman Bertazi
2020-09-24 11:24       ` Peter Zijlstra [this message]
2020-09-22 19:44   ` Kees Cook
2020-09-23 20:18     ` Gabriel Krisman Bertazi
2020-09-23 20:49       ` Kees Cook
2020-09-25  8:00         ` Thomas Gleixner
2020-09-25 16:15           ` Gabriel Krisman Bertazi
2020-09-25 20:30             ` Kees Cook
2020-09-04 20:31 ` [PATCH v6 2/9] kernel: entry: Support TIF_SYSCAL_INTERCEPT on common entry code Gabriel Krisman Bertazi
2020-09-07 10:16   ` Christian Brauner
2020-09-11  9:35   ` peterz
2020-09-11 20:11     ` Gabriel Krisman Bertazi
2020-09-04 20:31 ` [PATCH v6 3/9] x86: vdso: Expose sigreturn address on vdso to the kernel Gabriel Krisman Bertazi
2020-09-22 19:40   ` Kees Cook
2020-09-04 20:31 ` [PATCH v6 4/9] signal: Expose SYS_USER_DISPATCH si_code type Gabriel Krisman Bertazi
2020-09-07 10:15   ` Christian Brauner
2020-09-22 19:39   ` Kees Cook
2020-09-04 20:31 ` [PATCH v6 5/9] kernel: Implement selective syscall userspace redirection Gabriel Krisman Bertazi
2020-09-05 11:24   ` Matthew Wilcox
2020-09-11  9:44   ` peterz
2020-09-04 20:31 ` [PATCH v6 6/9] kernel: entry: Support Syscall User Dispatch for common syscall entry Gabriel Krisman Bertazi
2020-09-07 10:15   ` Christian Brauner
2020-09-07 14:15     ` Andy Lutomirski
2020-09-07 14:25       ` Christian Brauner
2020-09-07 20:20         ` Andy Lutomirski
2020-09-11  9:46   ` peterz
2020-09-04 20:31 ` [PATCH v6 7/9] x86: Enable Syscall User Dispatch Gabriel Krisman Bertazi
2020-09-22 19:37   ` Kees Cook
2020-09-23 20:23     ` Gabriel Krisman Bertazi
2020-09-04 20:31 ` [PATCH v6 8/9] selftests: Add kselftest for syscall user dispatch Gabriel Krisman Bertazi
2020-09-22 19:35   ` Kees Cook
2020-09-04 20:31 ` [PATCH v6 9/9] doc: Document Syscall User Dispatch Gabriel Krisman Bertazi
2020-09-22 19:35   ` Kees Cook

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