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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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14
include/asm-mips/fixmap.h
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@@ -45,8 +45,16 @@
* fix-mapped?
*/
enum fixed_addresses {
#define FIX_N_COLOURS 8
FIX_CMAP_BEGIN,
#ifdef CONFIG_MIPS_MT_SMTC
FIX_CMAP_END = FIX_CMAP_BEGIN + (FIX_N_COLOURS * NR_CPUS),
#else
FIX_CMAP_END = FIX_CMAP_BEGIN + FIX_N_COLOURS,
#endif
#ifdef CONFIG_HIGHMEM
FIX_KMAP_BEGIN, /* reserved pte's for temporary kernel mappings */
/* reserved pte's for temporary kernel mappings */
FIX_KMAP_BEGIN = FIX_CMAP_END + 1,
FIX_KMAP_END = FIX_KMAP_BEGIN+(KM_TYPE_NR*NR_CPUS)-1,
#endif
__end_of_fixed_addresses
@@ -70,9 +78,9 @@ extern void __set_fixmap (enum fixed_addresses idx,
* at the top of mem..
*/
#if defined(CONFIG_CPU_TX39XX) || defined(CONFIG_CPU_TX49XX)
#define FIXADDR_TOP (0xff000000UL - 0x2000)
#define FIXADDR_TOP ((unsigned long)(long)(int)(0xff000000 - 0x20000))
#else
#define FIXADDR_TOP (0xffffe000UL)
#define FIXADDR_TOP ((unsigned long)(long)(int)0xfffe0000)
#endif
#define FIXADDR_SIZE (__end_of_fixed_addresses << PAGE_SHIFT)
#define FIXADDR_START (FIXADDR_TOP - FIXADDR_SIZE)