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authorCatalin Marinas <catalin.marinas@arm.com>2010-09-13 16:03:21 +0100
committerRussell King <rmk+kernel@arm.linux.org.uk>2010-11-04 15:44:31 +0000
commit247055aa21ffef1c49dd64710d5e94c2aee19b58 (patch)
treee9e026b96597d080de4c16bb88c17b0495c61904 /arch/arm/kernel/entry-armv.S
parentff8b16d7e15a8ba2a6086645614a483e048e3fbf (diff)
downloadlinux-linaro-stable-247055aa21ffef1c49dd64710d5e94c2aee19b58.tar.gz
ARM: 6384/1: Remove the domain switching on ARMv6k/v7 CPUs
This patch removes the domain switching functionality via the set_fs and __switch_to functions on cores that have a TLS register. Currently, the ioremap and vmalloc areas share the same level 1 page tables and therefore have the same domain (DOMAIN_KERNEL). When the kernel domain is modified from Client to Manager (via the __set_fs or in the __switch_to function), the XN (eXecute Never) bit is overridden and newer CPUs can speculatively prefetch the ioremap'ed memory. Linux performs the kernel domain switching to allow user-specific functions (copy_to/from_user, get/put_user etc.) to access kernel memory. In order for these functions to work with the kernel domain set to Client, the patch modifies the LDRT/STRT and related instructions to the LDR/STR ones. The user pages access rights are also modified for kernel read-only access rather than read/write so that the copy-on-write mechanism still works. CPU_USE_DOMAINS gets disabled only if the hardware has a TLS register (CPU_32v6K is defined) since writing the TLS value to the high vectors page isn't possible. The user addresses passed to the kernel are checked by the access_ok() function so that they do not point to the kernel space. Tested-by: Anton Vorontsov <cbouatmailru@gmail.com> Cc: Tony Lindgren <tony@atomide.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'arch/arm/kernel/entry-armv.S')
-rw-r--r--arch/arm/kernel/entry-armv.S4
1 files changed, 2 insertions, 2 deletions
diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S
index c09e3573c5de..35f3f20d6731 100644
--- a/arch/arm/kernel/entry-armv.S
+++ b/arch/arm/kernel/entry-armv.S
@@ -735,7 +735,7 @@ ENTRY(__switch_to)
THUMB( stmia ip!, {r4 - sl, fp} ) @ Store most regs on stack
THUMB( str sp, [ip], #4 )
THUMB( str lr, [ip], #4 )
-#ifdef CONFIG_MMU
+#ifdef CONFIG_CPU_USE_DOMAINS
ldr r6, [r2, #TI_CPU_DOMAIN]
#endif
set_tls r3, r4, r5
@@ -744,7 +744,7 @@ ENTRY(__switch_to)
ldr r8, =__stack_chk_guard
ldr r7, [r7, #TSK_STACK_CANARY]
#endif
-#ifdef CONFIG_MMU
+#ifdef CONFIG_CPU_USE_DOMAINS
mcr p15, 0, r6, c3, c0, 0 @ Set domain register
#endif
mov r5, r0