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authorWill Deacon <will.deacon@arm.com>2012-09-01 05:22:12 +0100
committerWill Deacon <will.deacon@arm.com>2012-11-09 14:13:20 +0000
commit26ffd0d43b186b0d5186354da8714a1c2d360df0 (patch)
tree405c83d298530b65bb64630da52cfb368927691a /arch/arm/mm
parentdbf62d50067e55a782583fe53c3d2a3d98b1f6f3 (diff)
ARM: mm: introduce present, faulting entries for PAGE_NONE
PROT_NONE mappings apply the page protection attributes defined by _P000 which translate to PAGE_NONE for ARM. These attributes specify an XN, RDONLY pte that is inaccessible to userspace. However, on kernels configured without support for domains, such a pte *is* accessible to the kernel and can be read via get_user, allowing tasks to read PROT_NONE pages via syscalls such as read/write over a pipe. This patch introduces a new software pte flag, L_PTE_NONE, that is set to identify faulting, present entries. Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to 'arch/arm/mm')
-rw-r--r--arch/arm/mm/proc-macros.S4
-rw-r--r--arch/arm/mm/proc-v7-2level.S4
-rw-r--r--arch/arm/mm/proc-v7-3level.S3
3 files changed, 11 insertions, 0 deletions
diff --git a/arch/arm/mm/proc-macros.S b/arch/arm/mm/proc-macros.S
index b29a2265af0..eb6aa73bc8b 100644
--- a/arch/arm/mm/proc-macros.S
+++ b/arch/arm/mm/proc-macros.S
@@ -167,6 +167,10 @@
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
diff --git a/arch/arm/mm/proc-v7-2level.S b/arch/arm/mm/proc-v7-2level.S
index e755e9f8d1b..6d98c13ab82 100644
--- a/arch/arm/mm/proc-v7-2level.S
+++ b/arch/arm/mm/proc-v7-2level.S
@@ -101,6 +101,10 @@ ENTRY(cpu_v7_set_pte_ext)
tst r1, #L_PTE_YOUNG
tstne r1, #L_PTE_VALID
+#ifndef CONFIG_CPU_USE_DOMAINS
+ eorne r1, r1, #L_PTE_NONE
+ tstne r1, #L_PTE_NONE
+#endif
moveq r3, #0
ARM( str r3, [r0, #2048]! )
diff --git a/arch/arm/mm/proc-v7-3level.S b/arch/arm/mm/proc-v7-3level.S
index d23d067e190..7b56386f949 100644
--- a/arch/arm/mm/proc-v7-3level.S
+++ b/arch/arm/mm/proc-v7-3level.S
@@ -67,6 +67,9 @@ ENTRY(cpu_v7_set_pte_ext)
#ifdef CONFIG_MMU
tst r2, #L_PTE_VALID
beq 1f
+ tst r3, #1 << (57 - 32) @ L_PTE_NONE
+ bicne r2, #L_PTE_VALID
+ bne 1f
tst r3, #1 << (55 - 32) @ L_PTE_DIRTY
orreq r2, #L_PTE_RDONLY
1: strd r2, r3, [r0]