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authorCatalin Marinas <catalin.marinas@arm.com>2010-09-13 17:03:21 +0200
committerRussell King <rmk+kernel@arm.linux.org.uk>2010-11-04 16:44:31 +0100
commit247055aa21ffef1c49dd64710d5e94c2aee19b58 (patch)
treee9e026b96597d080de4c16bb88c17b0495c61904 /arch/arm/mm/proc-macros.S
parentvmstat: fix offset calculation on void* (diff)
downloadlinux-247055aa21ffef1c49dd64710d5e94c2aee19b58.tar.xz
linux-247055aa21ffef1c49dd64710d5e94c2aee19b58.zip
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/mm/proc-macros.S')
-rw-r--r--arch/arm/mm/proc-macros.S7
1 files changed, 7 insertions, 0 deletions
diff --git a/arch/arm/mm/proc-macros.S b/arch/arm/mm/proc-macros.S
index 7d63beaf9745..337f10256cd6 100644
--- a/arch/arm/mm/proc-macros.S
+++ b/arch/arm/mm/proc-macros.S
@@ -99,6 +99,10 @@
* 110x 0 1 0 r/w r/o
* 11x0 0 1 0 r/w r/o
* 1111 0 1 1 r/w r/w
+ *
+ * If !CONFIG_CPU_USE_DOMAINS, the following permissions are changed:
+ * 110x 1 1 1 r/o r/o
+ * 11x0 1 1 1 r/o r/o
*/
.macro armv6_mt_table pfx
\pfx\()_mt_table:
@@ -138,8 +142,11 @@
tst r1, #L_PTE_USER
orrne r3, r3, #PTE_EXT_AP1
+#ifdef CONFIG_CPU_USE_DOMAINS
+ @ allow kernel read/write access to read-only user pages
tstne r3, #PTE_EXT_APX
bicne r3, r3, #PTE_EXT_APX | PTE_EXT_AP0
+#endif
tst r1, #L_PTE_EXEC
orreq r3, r3, #PTE_EXT_XN