Re: [PATCH 3/3] MIPS: Fix COW D-cache aliasing on fork

From: Ralf Baechle
Date: Sat Oct 21 2006 - 22:38:32 EST


With parts of the previous patch 3/3 just having been applied this new
patch replaces it.

< ---- snip ---- >

From: Atsushi Nemoto <anemo@xxxxxxxxxxxxx>

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.

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

Signed-off-by: Atsushi Nemoto <anemo@xxxxxxxxxxxxx>
Signed-off-by: Ralf Baechle <ralf@xxxxxxxxxxxxxx>

arch/mips/mm/init.c | 25 +++++++++++++++++++++++++
include/asm-mips/page.h | 17 ++++++-----------
2 files changed, 31 insertions(+), 11 deletions(-)

Index: upstream-alias/arch/mips/mm/init.c
===================================================================
--- upstream-alias.orig/arch/mips/mm/init.c 2006-10-22 03:08:41.000000000 +0100
+++ upstream-alias/arch/mips/mm/init.c 2006-10-22 03:08:45.000000000 +0100
@@ -203,6 +203,31 @@ static inline void kunmap_coherent(struc
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)
Index: upstream-alias/include/asm-mips/page.h
===================================================================
--- upstream-alias.orig/include/asm-mips/page.h 2006-10-22 03:08:41.000000000 +0100
+++ upstream-alias/include/asm-mips/page.h 2006-10-22 03:08:45.000000000 +0100
@@ -34,8 +34,6 @@

#ifndef __ASSEMBLY__

-#include <asm/cpu-features.h>
-
extern void clear_page(void * page);
extern void copy_page(void * to, void * from);

@@ -59,16 +57,13 @@ static inline void clear_user_page(void
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..
-
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