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authorWill Deacon <will.deacon@arm.com>2011-05-26 11:23:43 +0100
committerRussell King <rmk+kernel@arm.linux.org.uk>2011-05-26 12:14:33 +0100
commit52af9c6cd863fe37d1103035ec7ee22ac1296458 (patch)
treefd6b4e6d7b3bc2881422fb5e735c5b9eda62662a /arch/arm
parentd427958a46af24f75d0017c45eadd172273bbf33 (diff)
downloadlinux-linaro-stable-52af9c6cd863fe37d1103035ec7ee22ac1296458.tar.gz
ARM: 6943/1: mm: use TTBR1 instead of reserved context ID
On ARMv7 CPUs that cache first level page table entries (like the Cortex-A15), using a reserved ASID while changing the TTBR or flushing the TLB is unsafe. This is because the CPU may cache the first level entry as the result of a speculative memory access while the reserved ASID is assigned. After the process owning the page tables dies, the memory will be reallocated and may be written with junk values which can be interpreted as global, valid PTEs by the processor. This will result in the TLB being populated with bogus global entries. This patch avoids the use of a reserved context ID in the v7 switch_mm and ASID rollover code by temporarily using the swapper_pg_dir pointed at by TTBR1, which contains only global entries that are not tagged with ASIDs. Acked-by: Catalin Marinas <catalin.marinas@arm.com> 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')
-rw-r--r--arch/arm/mm/context.c11
-rw-r--r--arch/arm/mm/proc-v7.S10
2 files changed, 10 insertions, 11 deletions
diff --git a/arch/arm/mm/context.c b/arch/arm/mm/context.c
index b0ee9ba3cfab..0d86298c7279 100644
--- a/arch/arm/mm/context.c
+++ b/arch/arm/mm/context.c
@@ -24,9 +24,7 @@ DEFINE_PER_CPU(struct mm_struct *, current_mm);
/*
* We fork()ed a process, and we need a new context for the child
- * to run in. We reserve version 0 for initial tasks so we will
- * always allocate an ASID. The ASID 0 is reserved for the TTBR
- * register changing sequence.
+ * to run in.
*/
void __init_new_context(struct task_struct *tsk, struct mm_struct *mm)
{
@@ -36,8 +34,11 @@ void __init_new_context(struct task_struct *tsk, struct mm_struct *mm)
static void flush_context(void)
{
- /* set the reserved ASID before flushing the TLB */
- asm("mcr p15, 0, %0, c13, c0, 1\n" : : "r" (0));
+ u32 ttb;
+ /* Copy TTBR1 into TTBR0 */
+ asm volatile("mrc p15, 0, %0, c2, c0, 1\n"
+ "mcr p15, 0, %0, c2, c0, 0"
+ : "=r" (ttb));
isb();
local_flush_tlb_all();
if (icache_is_vivt_asid_tagged()) {
diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S
index 3c3867850a30..b3b566ec83d3 100644
--- a/arch/arm/mm/proc-v7.S
+++ b/arch/arm/mm/proc-v7.S
@@ -108,18 +108,16 @@ ENTRY(cpu_v7_switch_mm)
#ifdef CONFIG_ARM_ERRATA_430973
mcr p15, 0, r2, c7, c5, 6 @ flush BTAC/BTB
#endif
-#ifdef CONFIG_ARM_ERRATA_754322
- dsb
-#endif
- mcr p15, 0, r2, c13, c0, 1 @ set reserved context ID
- isb
-1: mcr p15, 0, r0, c2, c0, 0 @ set TTB 0
+ mrc p15, 0, r2, c2, c0, 1 @ load TTB 1
+ mcr p15, 0, r2, c2, c0, 0 @ into TTB 0
isb
#ifdef CONFIG_ARM_ERRATA_754322
dsb
#endif
mcr p15, 0, r1, c13, c0, 1 @ set context ID
isb
+ mcr p15, 0, r0, c2, c0, 0 @ set TTB 0
+ isb
#endif
mov pc, lr
ENDPROC(cpu_v7_switch_mm)