[MIPS] Fix aliasing bug in copy_to_user_page / copy_from_user_page
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>
diff --git a/arch/mips/mm/pgtable-32.c b/arch/mips/mm/pgtable-32.c
index 4bdaa05..4a61e62 100644
--- a/arch/mips/mm/pgtable-32.c
+++ b/arch/mips/mm/pgtable-32.c
@@ -31,9 +31,10 @@
void __init pagetable_init(void)
{
-#ifdef CONFIG_HIGHMEM
unsigned long vaddr;
- pgd_t *pgd, *pgd_base;
+ pgd_t *pgd_base;
+#ifdef CONFIG_HIGHMEM
+ pgd_t *pgd;
pud_t *pud;
pmd_t *pmd;
pte_t *pte;
@@ -44,7 +45,6 @@
pgd_init((unsigned long)swapper_pg_dir
+ sizeof(pgd_t) * USER_PTRS_PER_PGD);
-#ifdef CONFIG_HIGHMEM
pgd_base = swapper_pg_dir;
/*
@@ -53,6 +53,7 @@
vaddr = __fix_to_virt(__end_of_fixed_addresses - 1) & PMD_MASK;
fixrange_init(vaddr, 0, pgd_base);
+#ifdef CONFIG_HIGHMEM
/*
* Permanent kmaps:
*/