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: <20231024103601.GH31411@noisy.programming.kicks-ass.net>
Date:   Tue, 24 Oct 2023 12:36:01 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Jonathan Corbet <corbet@....net>,
        Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>, tony.luck@...el.com,
        ak@...ux.intel.com, tim.c.chen@...ux.intel.com,
        linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        kvm@...r.kernel.org,
        Alyssa Milburn <alyssa.milburn@...ux.intel.com>,
        Daniel Sneddon <daniel.sneddon@...ux.intel.com>,
        antonio.gomez.iglesias@...ux.intel.com,
        Alyssa Milburn <alyssa.milburn@...el.com>
Subject: Re: [PATCH  v2 1/6] x86/bugs: Add asm helpers for executing VERW

On Tue, Oct 24, 2023 at 01:08:21AM -0700, Pawan Gupta wrote:

> +.macro CLEAR_CPU_BUFFERS
> +	ALTERNATIVE "jmp .Lskip_verw_\@;", "jmp .Ldo_verw_\@", X86_FEATURE_CLEAR_CPU_BUF
> +		/* nopl __KERNEL_DS(%rax) */
> +		.byte 0x0f, 0x1f, 0x80, 0x00, 0x00;
> +.Lverw_arg_\@:	.word __KERNEL_DS;
> +.Ldo_verw_\@:	verw _ASM_RIP(.Lverw_arg_\@);
> +.Lskip_verw_\@:
> +.endm

Why can't this be:

	ALTERNATIVE "". "verw _ASM_RIP(mds_verw_sel)", X86_FEATURE_CLEAR_CPU_BUF

And have that mds_verw_sel thing be out-of-line ? That gives much better
code for the case where we don't need this.

Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ