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

[Ingo Molnar <mingo@xxxxxxxxxx>]

* Thomas Garnier <thgarnie@xxxxxxxxxx> 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

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel