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From: Andy Lutomirski <luto@kernel.org>
To: "Bae, Chang Seok" <chang.seok.bae@intel.com>
Cc: Andrew Lutomirski <luto@kernel.org>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@kernel.org>, Andi Kleen <ak@linux.intel.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	"Metzger, Markus T" <markus.t.metzger@intel.com>,
	"Ravi V. Shankar" <ravi.v.shankar@intel.com>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH V2 01/15] x86/fsgsbase/64: Introduce FS/GS base helper functions
Date: Thu, 31 May 2018 13:14:06 -0700	[thread overview]
Message-ID: <CALCETrXp5at9nQgz0x9TZOpajDGfbMhQXM-igBFjrQGJ_w_Wsg@mail.gmail.com> (raw)
In-Reply-To: <1527789525-8857-2-git-send-email-chang.seok.bae@intel.com>

On Thu, May 31, 2018 at 10:58 AM Chang S. Bae <chang.seok.bae@intel.com> wrote:
>
> With new helpers, FS/GS base access is centralized.
> Eventually, when FSGSBASE instruction enabled, it will
> be faster.
>
> The helpers are used on ptrace APIs (PTRACE_ARCH_PRCTL,
> PTRACE_SETREG, PTRACE_GETREG, etc). Idea is to keep
> the FS/GS-update mechanism organized.
>
> Notion of "active" and "inactive" are used to distinguish
> GS bases between "kernel" and "user". "inactive" GS base
> is the GS base, backed up at kernel entries, of inactive
> (user) task's.

I'm fine with the code, but the changelog entry is confusing.  A bunch
of the active helpers don't contain the term "active".

> +/*
> + * Read/write an (inactive) task's fsbase or gsbase. This returns
> + * the value that the FS/GS base would have (if the task were to be
> + * resumed). The current task is also supported.
> + */

Please change to "Read/write a task's fsbase or gsbase. ... These work
on current or on a different non-running task."

> +
> +unsigned long read_task_fsbase(struct task_struct *task)
> +{
> +       unsigned long fsbase;
> +
> +       if (task == current)
> +               fsbase = read_fsbase();
> +       else
> +               /*
> +                * XXX: This will not behave as expected if called
> +                * if fsindex != 0
> +                */
> +               fsbase = task->thread.fsbase;
> +

Please put braces around the if and else blocks whenever either of
them spans multiple lines.  Also, maybe change add a note to the
comment and/or the changelog that this is preserving an existing bug
and that it's fixed later in the series.

  reply	other threads:[~2018-05-31 20:14 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-31 17:58 [PATCH V2 00/15] x86: Enable FSGSBASE instructions Chang S. Bae
2018-05-31 17:58 ` [PATCH V2 01/15] x86/fsgsbase/64: Introduce FS/GS base helper functions Chang S. Bae
2018-05-31 20:14   ` Andy Lutomirski [this message]
2018-05-31 21:03     ` Bae, Chang Seok
2018-05-31 17:58 ` [PATCH V2 02/15] x86/fsgsbase/64: Make ptrace read FS/GS base accurately Chang S. Bae
2018-05-31 20:14   ` Andy Lutomirski
2018-05-31 20:31     ` hpa
2018-05-31 20:38       ` Andy Lutomirski
2018-05-31 17:58 ` [PATCH V2 03/15] x86/fsgsbase/64: Use FS/GS base helpers in core dump Chang S. Bae
2018-05-31 20:15   ` Andy Lutomirski
2018-05-31 21:03     ` Bae, Chang Seok
2018-05-31 17:58 ` [PATCH V2 04/15] x86/fsgsbase/64: Factor out load FS/GS segments from __switch_to Chang S. Bae
2018-05-31 20:16   ` Andy Lutomirski
2018-05-31 17:58 ` [PATCH V2 05/15] x86/vdso: Move out the CPU number store Chang S. Bae
2018-05-31 20:25   ` Andy Lutomirski
2018-05-31 21:06     ` Bae, Chang Seok
2018-06-05  7:02   ` [lkp-robot] [x86/vdso] f52001961d: BUG:kernel_hang_in_early-boot_stage,last_printk:Probing_EDD(edd=off_to_disable)...ok kernel test robot
2018-05-31 17:58 ` [PATCH V2 06/15] taint: Add taint for insecure Chang S. Bae
2018-05-31 20:25   ` Andy Lutomirski
2018-05-31 20:50     ` hpa
2018-05-31 17:58 ` [PATCH V2 07/15] x86/fsgsbase/64: Add 'unsafe_fsgsbase' to enable CR4.FSGSBASE Chang S. Bae
2018-05-31 17:58 ` [PATCH V2 08/15] x86/fsgsbase/64: Add intrinsics/macros for FSGSBASE instructions Chang S. Bae
2018-05-31 17:58 ` [PATCH V2 09/15] x86/fsgsbase/64: Enable FSGSBASE instructions in helper functions Chang S. Bae
2018-05-31 17:58 ` [PATCH V2 10/15] x86/fsgsbase/64: Preserve FS/GS state in __switch_to if FSGSBASE is on Chang S. Bae
2018-05-31 17:58 ` [PATCH V2 11/15] x86/fsgsbase/64: When copying a thread, use FSGSBASE if enabled Chang S. Bae
2018-05-31 17:58 ` [PATCH V2 12/15] x86/fsgsbase/64: Use per-CPU base as GS base on paranoid_entry Chang S. Bae
2018-05-31 17:58 ` [PATCH V2 13/15] x86/fsgsbase/64: Enable FSGSBASE by default and add a chicken bit Chang S. Bae
2018-05-31 17:58 ` [PATCH V2 14/15] x86/elf: Enumerate kernel FSGSBASE capability in AT_HWCAP2 Chang S. Bae
2018-05-31 17:58 ` [PATCH V2 15/15] x86/fsgsbase/64: Add documentation for FSGSBASE Chang S. Bae
2018-05-31 20:37 ` [PATCH V2 00/15] x86: Enable FSGSBASE instructions Andy Lutomirski
2018-05-31 21:11   ` Bae, Chang Seok

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