Subject: [PATCH 03/19] arm64: Add new asm macro copy_page

From: [email-masked] (James Morse)
Date: Wed, 20 Jan 2016 14:01:44 +0000

Hi Geoff,

On 15/01/16 19:18, Geoff Levand wrote:

Can I donate a commit message:

Kexec and hibernate need to copy pages of memory, but may not have all
of the kernel mapped, and are unable to call copy_page().

Convert copy_page() to a macro, so that it can be inlined in these
situations.

> Signed-off-by: Geoff Levand <[email-masked]>
> ---
>  arch/arm64/include/asm/assembler.h | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
> 
> diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
> index 21979a4..c47a623 100644
> --- a/arch/arm64/include/asm/assembler.h
> +++ b/arch/arm64/include/asm/assembler.h
> @@ -24,6 +24,7 @@
>  #define __ASM_ASSEMBLER_H
>  
>  #include <asm/asm-offsets.h>
> +#include <asm/page.h>
>  #include <asm/pgtable-hwdef.h>
>  #include <asm/ptrace.h>
>  #include <asm/thread_info.h>
> @@ -240,6 +241,24 @@ lr	.req	x30		// link register
>  	.endm
>  
>  /*
> + * copy_page - copy src to dest using temp registers t1-t8
> + */
> +	.macro copy_page dest:req src:req t1:req t2:req t3:req t4:req t5:req t6:req t7:req t8:req
> +1:	ldp	\t1, \t2, [\src]

Using '1' as a label here means callers can't jump back over it using
the same label. The convention with USER() and alternatives is to use
unlikely values like '9999'.

> +	ldp	\t3, \t4, [\src, #16]
> +	ldp	\t5, \t6, [\src, #32]
> +	ldp	\t7, \t8, [\src, #48]
> +	add	\src, \src, #64
> +	stnp	\t1, \t2, [\dest]
> +	stnp	\t3, \t4, [\dest, #16]
> +	stnp	\t5, \t6, [\dest, #32]
> +	stnp	\t7, \t8, [\dest, #48]
> +	add	\dest, \dest, #64
> +	tst	\src, #(PAGE_SIZE - 1)
> +	b.ne	1b
> +	.endm

It may be worth updating lib/copy_page.S to use this macro.

I will fix the code in hibernate to use this!

Thanks,

James