Openwall GNU/*/Linux - a small security-enhanced Linux distro for servers
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Date: Tue, 6 Aug 2019 07:08:51 +0200
From: Borislav Petkov <bp@...en8.de>
To: Thomas Garnier <thgarnie@...omium.org>
Cc: Kernel Hardening <kernel-hardening@...ts.openwall.com>,
	Kristen Carlson Accardi <kristen@...ux.intel.com>,
	Kees Cook <keescook@...omium.org>,
	Andy Lutomirski <luto@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, "H. Peter Anvin" <hpa@...or.com>,
	the arch/x86 maintainers <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v9 04/11] x86/entry/64: Adapt assembly for PIE support

On Mon, Aug 05, 2019 at 10:50:30AM -0700, Thomas Garnier wrote:
> I saw that %rdx was used for temporary usage and restored before the
> end so I assumed that it was not an option.

PUSH_AND_CLEAR_REGS saves all regs earlier so I think you should be
able to use others. Like SAVE_AND_SWITCH_TO_KERNEL_CR3/RESTORE_CR3, for
example, uses %r15 and %r14.

-- 
Regards/Gruss,
    Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.

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