Re: [PATCH v1 01/27] x86/crypto: Adapt assembly for PIE support

[Ingo Molnar <mingo@kernel.org>]

* 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