linux-kernel - Re: RFC, untested: handing of MSR immediates and MSRs on Xen

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: <4fba013b-6cce-d81c-dccf-994f56548629@gmail.com>
Date: Thu, 24 Oct 2024 00:08:02 +0200
From: Uros Bizjak <ubizjak@...il.com>
To: "H. Peter Anvin" <hpa@...or.com>, Xin Li <xin3.li@...el.com>,
 Xin Li <xin@...or.com>, Andrew Cooper <andrew.cooper3@...rix.com>
Cc: "x86@...nel.org" <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>,
 Peter Zijlstra <peterz@...radead.org>
Subject: Re: RFC, untested: handing of MSR immediates and MSRs on Xen

On 23. 10. 24 23:34, H. Peter Anvin wrote:
> And I of course forgot the include the actual code.

> 			ALTERNATIVE_2("ds wrmsr",
> 				      "wrmsrns",
> 				      X86_FEATURE_WRMSRNS,
> 				      "call %P[xen]",
> 				      X86_FEATURE_XENPV)

Please use %c asm operand modifier instead of %P. Please see comment in 
arch/x86/include/asm/alternative.h for the reason:

--q--
  * Use the %c operand modifier which is the generic way to print a bare
  * constant expression with all syntax-specific punctuation omitted. %P
  * is the x86-specific variant which can handle constants too, for
  * historical reasons, but it should be used primarily for PIC
  * references: i.e., if used for a function, it would add the PLT
  * suffix.
--/q--

Uros.