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From: Ingo Molnar <mingo@kernel.org>
To: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Andy Lutomirski <luto@amacapital.net>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Borislav Petkov <bp@alien8.de>, "H. Peter Anvin" <hpa@zytor.com>,
	Oleg Nesterov <oleg@redhat.com>,
	Frederic Weisbecker <fweisbec@gmail.com>,
	Alexei Starovoitov <ast@plumgrid.com>,
	Will Drewry <wad@chromium.org>, Kees Cook <keescook@chromium.org>,
	x86@kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] x86: save r11 into pt_regs->flags on SYSCALL64 fastpath
Date: Mon, 9 Mar 2015 17:02:32 +0100	[thread overview]
Message-ID: <20150309160232.GA21787@gmail.com> (raw)
In-Reply-To: <1425847750-23362-2-git-send-email-dvlasenk@redhat.com>


* Denys Vlasenko <dvlasenk@redhat.com> wrote:

> Before this patch, r11 was saved in pt_regs->r11.
> Which looks natural, but requires messy shuffling to/from iret frame
> whenever ptrace or e.g. iopl wants to modify flags - because
> that's how this register is used by SYSCALL/SYSRET.
> 
> This patch saves r11 in pt_regs->flags,
> and uses that value for SYSRET64 insn. Shuffling is eliminated.
> 
> stub_iopl is no longer needed: pt_regs->flags needs no fixing up.

Could you please split this into two patches: R11 saving, and 
stub_iopl removal?

For x86/asm changes we want as small changes as physically possible.

Thanks,

	Ingo

  reply	other threads:[~2015-03-09 16:02 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-03-08 20:49 [PATCH 0/2] x86: entry_64.S: steps towards simpler iret frame handling Denys Vlasenko
2015-03-08 20:49 ` [PATCH 1/2] x86: save r11 into pt_regs->flags on SYSCALL64 fastpath Denys Vlasenko
2015-03-09 16:02   ` Ingo Molnar [this message]
2015-03-08 20:49 ` [PATCH 2/2] x86: save user %rsp in pt_regs->sp " Denys Vlasenko
2015-03-09 16:18   ` Ingo Molnar

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