From: Borislav Petkov <bp@alien8.de>
To: Lai Jiangshan <jiangshanlai@gmail.com>,
Andy Lutomirski <luto@kernel.org>
Cc: 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: Thu, 7 Apr 2022 10:22:25 +0200 [thread overview]
Message-ID: <Yk6fQfgo975pW3t0@zn.tnic> (raw)
In-Reply-To: <CAJhGHyBFbtyUs-nf0+gWm2a3hiS5BxZ3jk=sbGNw-4ShB8AtzQ@mail.gmail.com>
On Thu, Apr 07, 2022 at 03:03:08PM +0800, Lai Jiangshan wrote:
> sync_regs() is called before the return address of error_entry()
> popped into %r12 while fixup_bad_iret() is called with the return
> address of error_entry() still on the stack. And the primitives of
> fixup_bad_iret() and sync_regs() are different which also means
> they are not the same way.
>
> After this change, they become the same way.
>
> IMO, sync_regs() is grace while fixup_bad_iret() is a bad C function
> or is not a pure C function because it is handling the return address
> of its parent function which is better done by the compiler or ASM
> code.
Maybe there was a reason it was done this way:
b645af2d5905 ("x86_64, traps: Rework bad_iret")
although I don't see anything relevant in the text explaining this.
Andy?
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
next prev parent reply other threads:[~2022-04-07 8:22 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-18 14:30 [PATCH V4 0/7] x86/entry: Clean up entry code Lai Jiangshan
2022-03-18 14:30 ` [PATCH V4 1/7] x86/traps: Move pt_regs only in fixup_bad_iret() Lai Jiangshan
2022-04-06 19:00 ` Borislav Petkov
2022-04-07 7:03 ` Lai Jiangshan
2022-04-07 8:22 ` Borislav Petkov [this message]
2022-04-07 13:18 ` Borislav Petkov
2022-04-08 1:56 ` Lai Jiangshan
2022-04-11 9:36 ` Borislav Petkov
2022-03-18 14:30 ` [PATCH V4 2/7] x86/entry: Switch the stack after error_entry() returns Lai Jiangshan
2022-04-11 9:35 ` Borislav Petkov
2022-04-11 11:48 ` Lai Jiangshan
2022-03-18 14:30 ` [PATCH V4 3/7] x86/entry: move PUSH_AND_CLEAR_REGS out of error_entry Lai Jiangshan
2022-03-18 14:30 ` [PATCH V4 4/7] x86/entry: Move cld to the start of idtentry Lai Jiangshan
2022-03-18 14:30 ` [PATCH V4 5/7] x86/entry: Don't call error_entry for XENPV Lai Jiangshan
2022-03-18 14:30 ` [PATCH V4 6/7] x86/entry: Convert SWAPGS to swapgs and remove the definition of SWAPGS Lai Jiangshan
2022-03-18 14:30 ` [PATCH V4 7/7] x86/entry: Use idtentry macro for entry_INT80_compat Lai Jiangshan
2022-04-06 15:57 ` [PATCH V4 0/7] x86/entry: Clean up entry code Lai Jiangshan
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