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[MIPS] Fix aliasing bug in copy_to_user_page / copy_from_user_page

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The current implementation uses a sequence of a cacheflush and a copy.
This is racy in case of a multithreaded debuggee and renders GDB
virtually unusable.

Aside this fixes a performance hog rendering access to /proc/cmdline very
slow and resulting in a enough cache stalls for the 34K AP/SP programming
model to make the bare metal code on the non-Linux VPE miss RT deadlines.

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

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
This commit is contained in:
Ralf Baechle
2006-10-21 23:17:35 +01:00
parent 224dc50ece
commit f8829caee3
5 changed files with 190 additions and 28 deletions
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19
include/asm-mips/cacheflush.h
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@@ -55,24 +55,13 @@ extern void (*flush_icache_range)(unsigned long start, unsigned long end);
#define flush_cache_vmap(start, end) flush_cache_all()
#define flush_cache_vunmap(start, end) flush_cache_all()
static inline void copy_to_user_page(struct vm_area_struct *vma,
extern void copy_to_user_page(struct vm_area_struct *vma,
struct page *page, unsigned long vaddr, void *dst, const void *src,
unsigned long len)
{
if (cpu_has_dc_aliases)
flush_cache_page(vma, vaddr, page_to_pfn(page));
memcpy(dst, src, len);
__flush_icache_page(vma, page);
}
unsigned long len);
static inline void copy_from_user_page(struct vm_area_struct *vma,
extern void copy_from_user_page(struct vm_area_struct *vma,
struct page *page, unsigned long vaddr, void *dst, const void *src,
unsigned long len)
{
if (cpu_has_dc_aliases)
flush_cache_page(vma, vaddr, page_to_pfn(page));
memcpy(dst, src, len);
}
unsigned long len);
extern void (*flush_cache_sigtramp)(unsigned long addr);
extern void (*flush_icache_all)(void);