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authorWill Deacon <will.deacon@arm.com>2014-02-07 19:12:27 +0100
committerRussell King <rmk+kernel@arm.linux.org.uk>2014-02-10 12:48:13 +0100
commitb6ccb9803e90c16b212cf4ed62913a7591e79a39 (patch)
treee077cbf203e4b7fbaaa0e0b4807b01c0f028405a /arch/arm/mm/proc-macros.S
parentARM: 7951/1: uaccess: use CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS (diff)
downloadlinux-b6ccb9803e90c16b212cf4ed62913a7591e79a39.tar.xz
linux-b6ccb9803e90c16b212cf4ed62913a7591e79a39.zip
ARM: 7954/1: mm: remove remaining domain support from ARMv6
CPU_32v6 currently selects CPU_USE_DOMAINS if CPU_V6 and MMU. This is because ARM 1136 r0pX CPUs lack the v6k extensions, and therefore do not have hardware thread registers. The lack of these registers requires the kernel to update the vectors page at each context switch in order to write a new TLS pointer. This write must be done via the userspace mapping, since aliasing caches can lead to expensive flushing when using kmap. Finally, this requires the vectors page to be mapped r/w for kernel and r/o for user, which has implications for things like put_user which must trigger CoW appropriately when targetting user pages. The upshot of all this is that a v6/v7 kernel makes use of domains to segregate kernel and user memory accesses. This has the nasty side-effect of making device mappings executable, which has been observed to cause subtle bugs on recent cores (e.g. Cortex-A15 performing a speculative instruction fetch from the GIC and acking an interrupt in the process). This patch solves this problem by removing the remaining domain support from ARMv6. A new memory type is added specifically for the vectors page which allows that page (and only that page) to be mapped as user r/o, kernel r/w. All other user r/o pages are mapped also as kernel r/o. Patch co-developed with Russell King. Cc: <stable@vger.kernel.org> Signed-off-by: Will Deacon <will.deacon@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.S19
1 files changed, 6 insertions, 13 deletions
diff --git a/arch/arm/mm/proc-macros.S b/arch/arm/mm/proc-macros.S
index e3c48a3fe063..ee1d80593958 100644
--- a/arch/arm/mm/proc-macros.S
+++ b/arch/arm/mm/proc-macros.S
@@ -112,13 +112,9 @@
* 100x 1 0 1 r/o no acc
* 10x0 1 0 1 r/o no acc
* 1011 0 0 1 r/w no acc
- * 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
+ * 1111 0 1 1 r/w r/w
*/
.macro armv6_mt_table pfx
\pfx\()_mt_table:
@@ -137,7 +133,7 @@
.long PTE_EXT_TEX(2) @ L_PTE_MT_DEV_NONSHARED
.long 0x00 @ unused
.long 0x00 @ unused
- .long 0x00 @ unused
+ .long PTE_CACHEABLE | PTE_BUFFERABLE | PTE_EXT_APX @ L_PTE_MT_VECTORS
.endm
.macro armv6_set_pte_ext pfx
@@ -158,24 +154,21 @@
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
+
+ @ user read-only -> kernel read-only
+ bicne r3, r3, #PTE_EXT_AP0
tst r1, #L_PTE_XN
orrne r3, r3, #PTE_EXT_XN
- orr r3, r3, r2
+ eor r3, r3, r2
tst r1, #L_PTE_YOUNG
tstne r1, #L_PTE_PRESENT
moveq r3, #0
-#ifndef CONFIG_CPU_USE_DOMAINS
tstne r1, #L_PTE_NONE
movne r3, #0
-#endif
str r3, [r0]
mcr p15, 0, r0, c7, c10, 1 @ flush_pte