linux-kernel - Re: [PATCH V3 4/7] x86/entry: move PUSH_AND_CLEAR_REGS out of error

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <YjH9M3MBn+j/MwPJ@hirez.programming.kicks-ass.net>
Date:   Wed, 16 Mar 2022 16:07:31 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Lai Jiangshan <jiangshanlai@...il.com>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        Borislav Petkov <bp@...en8.de>,
        Lai Jiangshan <jiangshan.ljs@...group.com>,
        Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH V3 4/7] x86/entry: move PUSH_AND_CLEAR_REGS out of
 error_entry

On Tue, Mar 15, 2022 at 03:39:46PM +0800, Lai Jiangshan wrote:
> From: Lai Jiangshan <jiangshan.ljs@...group.com>
> 
> Moving PUSH_AND_CLEAR_REGS out of error_entry doesn't change any
> functionality.
> 
> It makes error_entry() do not fiddle with the stack.
> 
> It will enlarge the size:
> 
> size arch/x86/entry/entry_64.o.before:
>    text	   data	    bss	    dec	    hex	filename
>   17916	    384	      0	  18300	   477c	arch/x86/entry/entry_64.o
> 
> size --format=SysV arch/x86/entry/entry_64.o.before:
> .entry.text                      5528      0
> .orc_unwind                      6456      0
> .orc_unwind_ip                   4304      0
> 
> size arch/x86/entry/entry_64.o.after:
>    text	   data	    bss	    dec	    hex	filename
>   26868	    384	      0	  27252	   6a74	arch/x86/entry/entry_64.o
> 
> size --format=SysV arch/x86/entry/entry_64.o.after:
> .entry.text                      8200      0
> .orc_unwind                     10224      0
> .orc_unwind_ip                   6816      0
> 
> But .entry.text in x86_64 is 2M aligned, enlarging it to 8.2k doesn't
> enlarge the final text size.

So I don't much care about the orc data, that's only used when
unwinding, a relatively rare occasion, anyway. But the text increase
does bother me a little, this can blow up I$ misses on syscall heavy
workloads.