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Commit bcd02280 authored by Atsushi Nemoto's avatar Atsushi Nemoto Committed by Linus Torvalds
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[PATCH] MIPS: Fix COW D-cache aliasing on fork 



Provide a custom copy_user_highpage() to deal with aliasing issues on
MIPS.  It uses kmap_coherent() to map an user page for kernel with same
color.  Rewrite copy_to_user_page() and copy_from_user_page() with the
new interfaces to avoid extra cache flushing.

The main part of this patch was originally written by Ralf Baechle;
Atushi Nemoto did the the debugging.

Signed-off-by: default avatarAtsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: default avatarRalf Baechle <ralf@linux-mips.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 9de455b2

arch/mips/mm/init.c

+25 −0
Original line number Diff line number Diff line
@@ -203,6 +203,31 @@ static inline void kunmap_coherent(struct page *page) 
	preempt_check_resched();

}



void copy_user_highpage(struct page *to, struct page *from,

	unsigned long vaddr, struct vm_area_struct *vma)

{

	void *vfrom, *vto;



	vto = kmap_atomic(to, KM_USER1);

	if (cpu_has_dc_aliases) {

		vfrom = kmap_coherent(from, vaddr);

		copy_page(vto, vfrom);

		kunmap_coherent(from);

	} else {

		vfrom = kmap_atomic(from, KM_USER0);

		copy_page(vto, vfrom);

		kunmap_atomic(vfrom, KM_USER0);

	}

	if (((vma->vm_flags & VM_EXEC) && !cpu_has_ic_fills_f_dc) ||

	    pages_do_alias((unsigned long)vto, vaddr & PAGE_MASK))

		flush_data_cache_page((unsigned long)vto);

	kunmap_atomic(vto, KM_USER1);

	/* Make sure this page is cleared on other CPU's too before using it */

	smp_wmb();

}



EXPORT_SYMBOL(copy_user_highpage);



void copy_to_user_page(struct vm_area_struct *vma,

	struct page *page, unsigned long vaddr, void *dst, const void *src,

	unsigned long len)

include/asm-mips/page.h

+6 −10
Original line number Diff line number Diff line
@@ -35,7 +35,6 @@ 
#ifndef __ASSEMBLY__



#include <linux/pfn.h>

#include <asm/cpu-features.h>

#include <asm/io.h>



extern void clear_page(void * page);
@@ -61,16 +60,13 @@ static inline void clear_user_page(void *addr, unsigned long vaddr, 
		flush_data_cache_page((unsigned long)addr);

}



static inline void copy_user_page(void *vto, void *vfrom, unsigned long vaddr,

	struct page *to)

{

	extern void (*flush_data_cache_page)(unsigned long addr);

extern void copy_user_page(void *vto, void *vfrom, unsigned long vaddr,

	struct page *to);

struct vm_area_struct;

extern void copy_user_highpage(struct page *to, struct page *from,

	unsigned long vaddr, struct vm_area_struct *vma);



	copy_page(vto, vfrom);

	if (!cpu_has_ic_fills_f_dc ||

	    pages_do_alias((unsigned long)vto, vaddr & PAGE_MASK))

		flush_data_cache_page((unsigned long)vto);

}

#define __HAVE_ARCH_COPY_USER_HIGHPAGE



/*

 * These are used to make use of C type-checking..