Openwall GNU/*/Linux - a small security-enhanced Linux distro for servers
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date: Fri, 20 Oct 2017 10:26:46 +0200
From: Ingo Molnar <mingo@...nel.org>
To: Thomas Garnier <thgarnie@...gle.com>
Cc: Herbert Xu <herbert@...dor.apana.org.au>,
	"David S . Miller" <davem@...emloft.net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, "H . Peter Anvin" <hpa@...or.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Josh Poimboeuf <jpoimboe@...hat.com>, Arnd Bergmann <arnd@...db.de>,
	Kees Cook <keescook@...omium.org>,
	Andrey Ryabinin <aryabinin@...tuozzo.com>,
	Matthias Kaehlcke <mka@...omium.org>,
	Tom Lendacky <thomas.lendacky@....com>,
	Andy Lutomirski <luto@...nel.org>,
	"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
	Borislav Petkov <bp@...e.de>,
	"Rafael J . Wysocki" <rjw@...ysocki.net>,
	Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
	Juergen Gross <jgross@...e.com>, Chris Wright <chrisw@...s-sol.org>,
	Alok Kataria <akataria@...are.com>,
	Rusty Russell <rusty@...tcorp.com.au>, Tejun Heo <tj@...nel.org>,
	Christoph Lameter <cl@...ux.com>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	Paul Gortmaker <paul.gortmaker@...driver.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Alexey Dobriyan <adobriyan@...il.com>,
	"Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>,
	Nicolas Pitre <nicolas.pitre@...aro.org>,
	Borislav Petkov <bp@...en8.de>,
	"Luis R . Rodriguez" <mcgrof@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Christopher Li <sparse@...isli.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Jason Baron <jbaron@...mai.com>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Dou Liyang <douly.fnst@...fujitsu.com>,
	"Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
	Lukas Wunner <lukas@...ner.de>,
	Masahiro Yamada <yamada.masahiro@...ionext.com>,
	Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Markus Trippelsdorf <markus@...ppelsdorf.de>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Radim Krčmář <rkrcmar@...hat.com>,
	Joerg Roedel <joro@...tes.org>, Rik van Riel <riel@...hat.com>,
	David Howells <dhowells@...hat.com>,
	Ard Biesheuvel <ard.biesheuvel@...aro.org>,
	Waiman Long <longman@...hat.com>, Kyle Huey <me@...ehuey.com>,
	Jonathan Corbet <corbet@....net>, Michal Hocko <mhocko@...e.com>,
	Peter Foley <pefoley2@...oley.com>, Paul Bolle <pebolle@...cali.nl>,
	Jiri Kosina <jkosina@...e.cz>, "H . J . Lu" <hjl.tools@...il.com>,
	Rob Landley <rob@...dley.net>, Baoquan He <bhe@...hat.com>,
	Jan H . Schönherr <jschoenh@...zon.de>,
	Daniel Micay <danielmicay@...il.com>, x86@...nel.org,
	linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-pm@...r.kernel.org, virtualization@...ts.linux-foundation.org,
	xen-devel@...ts.xenproject.org, linux-arch@...r.kernel.org,
	linux-sparse@...r.kernel.org, kvm@...r.kernel.org,
	linux-doc@...r.kernel.org, kernel-hardening@...ts.openwall.com
Subject: Re: [PATCH v1 06/27] x86/entry/64: Adapt assembly for PIE support


* Thomas Garnier <thgarnie@...gle.com> wrote:

> Change the assembly code to use only relative references of symbols for the
> kernel to be PIE compatible.
> 
> Position Independent Executable (PIE) support will allow to extended the
> KASLR randomization range below the -2G memory limit.
> 
> Signed-off-by: Thomas Garnier <thgarnie@...gle.com>
> ---
>  arch/x86/entry/entry_64.S | 22 +++++++++++++++-------
>  1 file changed, 15 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
> index 49167258d587..15bd5530d2ae 100644
> --- a/arch/x86/entry/entry_64.S
> +++ b/arch/x86/entry/entry_64.S
> @@ -194,12 +194,15 @@ entry_SYSCALL_64_fastpath:
>  	ja	1f				/* return -ENOSYS (already in pt_regs->ax) */
>  	movq	%r10, %rcx
>  
> +	/* Ensures the call is position independent */
> +	leaq	sys_call_table(%rip), %r11
> +
>  	/*
>  	 * This call instruction is handled specially in stub_ptregs_64.
>  	 * It might end up jumping to the slow path.  If it jumps, RAX
>  	 * and all argument registers are clobbered.
>  	 */
> -	call	*sys_call_table(, %rax, 8)
> +	call	*(%r11, %rax, 8)
>  .Lentry_SYSCALL_64_after_fastpath_call:
>  
>  	movq	%rax, RAX(%rsp)
> @@ -334,7 +337,8 @@ ENTRY(stub_ptregs_64)
>  	 * RAX stores a pointer to the C function implementing the syscall.
>  	 * IRQs are on.
>  	 */
> -	cmpq	$.Lentry_SYSCALL_64_after_fastpath_call, (%rsp)
> +	leaq	.Lentry_SYSCALL_64_after_fastpath_call(%rip), %r11
> +	cmpq	%r11, (%rsp)
>  	jne	1f
>  
>  	/*
> @@ -1172,7 +1176,8 @@ ENTRY(error_entry)
>  	movl	%ecx, %eax			/* zero extend */
>  	cmpq	%rax, RIP+8(%rsp)
>  	je	.Lbstep_iret
> -	cmpq	$.Lgs_change, RIP+8(%rsp)
> +	leaq	.Lgs_change(%rip), %rcx
> +	cmpq	%rcx, RIP+8(%rsp)
>  	jne	.Lerror_entry_done
>  
>  	/*
> @@ -1383,10 +1388,10 @@ ENTRY(nmi)
>  	 * resume the outer NMI.
>  	 */
>  
> -	movq	$repeat_nmi, %rdx
> +	leaq	repeat_nmi(%rip), %rdx
>  	cmpq	8(%rsp), %rdx
>  	ja	1f
> -	movq	$end_repeat_nmi, %rdx
> +	leaq	end_repeat_nmi(%rip), %rdx
>  	cmpq	8(%rsp), %rdx
>  	ja	nested_nmi_out
>  1:
> @@ -1440,7 +1445,8 @@ nested_nmi:
>  	pushq	%rdx
>  	pushfq
>  	pushq	$__KERNEL_CS
> -	pushq	$repeat_nmi
> +	leaq	repeat_nmi(%rip), %rdx
> +	pushq	%rdx
>  
>  	/* Put stack back */
>  	addq	$(6*8), %rsp
> @@ -1479,7 +1485,9 @@ first_nmi:
>  	addq	$8, (%rsp)	/* Fix up RSP */
>  	pushfq			/* RFLAGS */
>  	pushq	$__KERNEL_CS	/* CS */
> -	pushq	$1f		/* RIP */
> +	pushq	%rax		/* Support Position Independent Code */
> +	leaq	1f(%rip), %rax	/* RIP */
> +	xchgq	%rax, (%rsp)	/* Restore RAX, put 1f */
>  	INTERRUPT_RETURN	/* continues at repeat_nmi below */
>  	UNWIND_HINT_IRET_REGS

This patch seems to add extra overhead to the syscall fast-path even when PIE is 
disabled, right?

Thanks,

	Ingo

Powered by blists - more mailing lists

Your e-mail address:

Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.