From: Ingo Molnar <mingo@kernel.org>
Subject: Re: [PATCH v1 01/27] x86/crypto: Adapt assembly for PIE support
Date: Fri, 20 Oct 2017 10:24:21 +0200
Message-ID: <20171020082420.lsvu7mqjrgnahm5t@gmail.com>
References: <20171011203027.11248-1-thgarnie@google.com>
 <20171011203027.11248-2-thgarnie@google.com>
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Cc: Herbert Xu <herbert@gondor.apana.org.au>,
	"David S . Miller" <davem@davemloft.net>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, "H . Peter Anvin" <hpa@zytor.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Josh Poimboeuf <jpoimboe@redhat.com>, Arnd Bergmann <arnd@arndb.de>,
	Kees Cook <keescook@chromium.org>,
	Andrey Ryabinin <aryabinin@virtuozzo.com>,
	Matthias Kaehlcke <mka@chromium.org>,
	Tom Lendacky <thomas.lendacky@amd.com>,
	Andy Lutomirski <luto@kernel.org>,
	"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
	Borislav Petkov <bp@suse.de>,
	"Rafael J . Wysocki" <rjw@rjwysocki.net>,
	Len Brown <len.brown@intel.com>, Pavel Machek <pavel@ucw.cz>,
	Juergen Gross <jgross@suse.com>, Chris Wright <chrisw@sous-sol.org>,
	Alok Kataria <akataria@vmware.com>,
	Rusty Russell <rusty@rustcorp.com.au>, Tejun Heo <tj@kernel.org>,
	Christoph Lameter <cl@linux.
To: Thomas Garnier <thgarnie@google.com>
Sender: Ingo Molnar <mingo.kernel.org@gmail.com>
Content-Disposition: inline
In-Reply-To: <20171011203027.11248-2-thgarnie@google.com>


* Thomas Garnier <thgarnie@google.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.

> diff --git a/arch/x86/crypto/aes-x86_64-asm_64.S b/arch/x86/crypto/aes-x86_64-asm_64.S
> index 8739cf7795de..86fa068e5e81 100644
> --- a/arch/x86/crypto/aes-x86_64-asm_64.S
> +++ b/arch/x86/crypto/aes-x86_64-asm_64.S
> @@ -48,8 +48,12 @@
>  #define R10	%r10
>  #define R11	%r11
>  
> +/* Hold global for PIE suport */
> +#define RBASE	%r12
> +
>  #define prologue(FUNC,KEY,B128,B192,r1,r2,r5,r6,r7,r8,r9,r10,r11) \
>  	ENTRY(FUNC);			\
> +	pushq	RBASE;			\
>  	movq	r1,r2;			\
>  	leaq	KEY+48(r8),r9;		\
>  	movq	r10,r11;		\
> @@ -74,54 +78,63 @@
>  	movl	r6 ## E,4(r9);		\
>  	movl	r7 ## E,8(r9);		\
>  	movl	r8 ## E,12(r9);		\
> +	popq	RBASE;			\
>  	ret;				\
>  	ENDPROC(FUNC);
>  
> +#define round_mov(tab_off, reg_i, reg_o) \
> +	leaq	tab_off(%rip), RBASE; \
> +	movl	(RBASE,reg_i,4), reg_o;
> +
> +#define round_xor(tab_off, reg_i, reg_o) \
> +	leaq	tab_off(%rip), RBASE; \
> +	xorl	(RBASE,reg_i,4), reg_o;
> +
>  #define round(TAB,OFFSET,r1,r2,r3,r4,r5,r6,r7,r8,ra,rb,rc,rd) \
>  	movzbl	r2 ## H,r5 ## E;	\
>  	movzbl	r2 ## L,r6 ## E;	\
> -	movl	TAB+1024(,r5,4),r5 ## E;\
> +	round_mov(TAB+1024, r5, r5 ## E)\
>  	movw	r4 ## X,r2 ## X;	\
> -	movl	TAB(,r6,4),r6 ## E;	\
> +	round_mov(TAB, r6, r6 ## E)	\
>  	roll	$16,r2 ## E;		\
>  	shrl	$16,r4 ## E;		\
>  	movzbl	r4 ## L,r7 ## E;	\
>  	movzbl	r4 ## H,r4 ## E;	\
>  	xorl	OFFSET(r8),ra ## E;	\
>  	xorl	OFFSET+4(r8),rb ## E;	\
> -	xorl	TAB+3072(,r4,4),r5 ## E;\
> -	xorl	TAB+2048(,r7,4),r6 ## E;\
> +	round_xor(TAB+3072, r4, r5 ## E)\
> +	round_xor(TAB+2048, r7, r6 ## E)\
>  	movzbl	r1 ## L,r7 ## E;	\
>  	movzbl	r1 ## H,r4 ## E;	\
> -	movl	TAB+1024(,r4,4),r4 ## E;\
> +	round_mov(TAB+1024, r4, r4 ## E)\
>  	movw	r3 ## X,r1 ## X;	\
>  	roll	$16,r1 ## E;		\
>  	shrl	$16,r3 ## E;		\
> -	xorl	TAB(,r7,4),r5 ## E;	\
> +	round_xor(TAB, r7, r5 ## E)	\
>  	movzbl	r3 ## L,r7 ## E;	\
>  	movzbl	r3 ## H,r3 ## E;	\
> -	xorl	TAB+3072(,r3,4),r4 ## E;\
> -	xorl	TAB+2048(,r7,4),r5 ## E;\
> +	round_xor(TAB+3072, r3, r4 ## E)\
> +	round_xor(TAB+2048, r7, r5 ## E)\
>  	movzbl	r1 ## L,r7 ## E;	\
>  	movzbl	r1 ## H,r3 ## E;	\
>  	shrl	$16,r1 ## E;		\
> -	xorl	TAB+3072(,r3,4),r6 ## E;\
> -	movl	TAB+2048(,r7,4),r3 ## E;\
> +	round_xor(TAB+3072, r3, r6 ## E)\
> +	round_mov(TAB+2048, r7, r3 ## E)\
>  	movzbl	r1 ## L,r7 ## E;	\
>  	movzbl	r1 ## H,r1 ## E;	\
> -	xorl	TAB+1024(,r1,4),r6 ## E;\
> -	xorl	TAB(,r7,4),r3 ## E;	\
> +	round_xor(TAB+1024, r1, r6 ## E)\
> +	round_xor(TAB, r7, r3 ## E)	\
>  	movzbl	r2 ## H,r1 ## E;	\
>  	movzbl	r2 ## L,r7 ## E;	\
>  	shrl	$16,r2 ## E;		\
> -	xorl	TAB+3072(,r1,4),r3 ## E;\
> -	xorl	TAB+2048(,r7,4),r4 ## E;\
> +	round_xor(TAB+3072, r1, r3 ## E)\
> +	round_xor(TAB+2048, r7, r4 ## E)\
>  	movzbl	r2 ## H,r1 ## E;	\
>  	movzbl	r2 ## L,r2 ## E;	\
>  	xorl	OFFSET+8(r8),rc ## E;	\
>  	xorl	OFFSET+12(r8),rd ## E;	\
> -	xorl	TAB+1024(,r1,4),r3 ## E;\
> -	xorl	TAB(,r2,4),r4 ## E;
> +	round_xor(TAB+1024, r1, r3 ## E)\
> +	round_xor(TAB, r2, r4 ## E)

This appears to be adding unconditional overhead to a function that was moved to 
assembly to improve its performance.

Thanks,

	Ingo