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authorDavid Daney <ddaney@caviumnetworks.com>2010-04-19 11:43:10 -0700
committerRalf Baechle <ralf@linux-mips.org>2010-04-30 20:52:41 +0100
commitc8f3cc0b65af00be5f84c6d4ee45007643322713 (patch)
tree9a1159172287b7fd921c5dd9a34d4c6b970187a0 /arch/mips/include
parentb0b4ce38a535ed3de5ec6fdd4f3c34435a1c1d1e (diff)
downloadlinux-2.6.34-ux500-c8f3cc0b65af00be5f84c6d4ee45007643322713.tar.gz
MIPS: Don't vmap things at address zero.
In the 64-bit kernel we use swapper_pg_dir for three different things. 1) xuseg mappings for kernel threads. 2) vmap mappings for all kernel-space accesses in xkseg. 3) vmap mappings for kernel modules in ksseg (kseg2). Due to how the TLB refill handlers work, any mapping established in xkseg or ksseg will also establish a xuseg mapping that should never be used by the kernel. In order to be able to use exceptions to trap NULL pointer dereferences, we need to ensure that nothing is mapped at address zero. Since vmap mappings in xkseg are reflected in xuseg, this means we need to ensure that there are no vmap mappings established at the start of xkseg. So we move back VMALLOC_START to avoid establishing vmap mappings at the start of xkseg. Signed-off-by: David Daney <ddaney@caviumnetworks.com> To: linux-mips@linux-mips.org Patchwork: http://patchwork.linux-mips.org/patch/1129/ Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Diffstat (limited to 'arch/mips/include')
-rw-r--r--arch/mips/include/asm/pgtable-64.h9
1 files changed, 7 insertions, 2 deletions
diff --git a/arch/mips/include/asm/pgtable-64.h b/arch/mips/include/asm/pgtable-64.h
index 26dc69d792a..1be4b0fa30d 100644
--- a/arch/mips/include/asm/pgtable-64.h
+++ b/arch/mips/include/asm/pgtable-64.h
@@ -120,9 +120,14 @@
#endif
#define FIRST_USER_ADDRESS 0UL
-#define VMALLOC_START MAP_BASE
+/*
+ * TLB refill handlers also map the vmalloc area into xuseg. Avoid
+ * the first couple of pages so NULL pointer dereferences will still
+ * reliably trap.
+ */
+#define VMALLOC_START (MAP_BASE + (2 * PAGE_SIZE))
#define VMALLOC_END \
- (VMALLOC_START + \
+ (MAP_BASE + \
min(PTRS_PER_PGD * PTRS_PER_PMD * PTRS_PER_PTE * PAGE_SIZE, \
(1UL << cpu_vmbits)) - (1UL << 32))