Re: [PATCH V4 1/7] x86/traps: Move pt_regs only in fixup_bad_iret()

From: Lai Jiangshan <jiangshanlai@gmail.com>
To: Borislav Petkov <bp@alien8.de>
Cc: Andy Lutomirski <luto@kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Josh Poimboeuf <jpoimboe@redhat.com>,
	Thomas Gleixner <tglx@linutronix.de>, X86 ML <x86@kernel.org>,
	Lai Jiangshan <jiangshan.ljs@antgroup.com>,
	Ingo Molnar <mingo@redhat.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Fenghua Yu <fenghua.yu@intel.com>,
	Thomas Tai <thomas.tai@oracle.com>,
	"Chang S. Bae" <chang.seok.bae@intel.com>,
	Masami Hiramatsu <mhiramat@kernel.org>
Subject: Re: [PATCH V4 1/7] x86/traps: Move pt_regs only in fixup_bad_iret()
Date: Fri, 8 Apr 2022 09:56:26 +0800	[thread overview]
Message-ID: <CAJhGHyByXaeaYqq54EY6YoNwf4DrupCXeZmtdi9ViYwmDx2ffQ@mail.gmail.com> (raw)
In-Reply-To: <Yk7kwzIv2YA+aO7y@zn.tnic>

On Thu, Apr 7, 2022 at 9:19 PM Borislav Petkov <bp@alien8.de> wrote:
>
> On Thu, Apr 07, 2022 at 10:22:25AM +0200, Borislav Petkov wrote:
> > Maybe there was a reason it was done this way:
>
> Ok, I went and singlestepped this code so that I can see what's going
> on.

[....]

>
> So your commit message should have been as simple as:
>
> "Always stash the address error_entry() is going to return to, in %r12
> and get rid of the void *error_entry_ret; slot in struct bad_iret_stack
> which was supposed to account for it and pt_regs pushed on the stack.
>
> After this, both functions can work on a struct pt_regs pointer
> directly."

Thank you for elaborating on the details and I will use this changelog.

Thanks
Lai

>
> In any case, I don't see why amluto would do this so this looks like a
> sensible cleanup to do.
>