linux-kernel - RE: [PATCH] x86/fsgsbase/64: Fix the base write helper functions

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Date:   Tue, 30 Oct 2018 17:54:48 +0000
From:   "Bae, Chang Seok" <chang.seok.bae@...el.com>
To:     Andy Lutomirski <luto@...nel.org>, Ingo Molnar <mingo@...nel.org>,
        "Thomas Gleixner" <tglx@...utronix.de>,
        "H . Peter Anvin" <hpa@...or.com>
CC:     Andi Kleen <ak@...ux.intel.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "Shankar, Ravi V" <ravi.v.shankar@...el.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] x86/fsgsbase/64: Fix the base write helper functions

> Factor out the code to change index from x86_fsbase_write_cpu() and
> x86_gsbase_write_cpu_inactive(). Now the code is located in
> do_arch_prctl_64().
> 
> The helper functions that purport to write the base register should just write the
> base register only. It shouldn't have magic optimizations to change the index.
> 
> putreg() in ptrace does not write the current task, but a stopped task.
> 

Wm, I just realized that the changelog should also clearly include this:
	"While at here, subsequently factor out the read for the current task's base 
	from x86_fsbase_read_task() and x86_gsbase_read_task() to do_arch_prctl_64()."
Sorry for this. Let me know if you feel it should go as a separate patch.

Chang