diff options
authorLorenzo Pieralisi <lorenzo.pieralisi@arm.com>2014-12-19 17:03:47 +0000
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2015-01-16 06:59:34 -0800
commit852cacf6bd83dd335d4138746dccb0497adfd3aa (patch)
parent219591c5764eff2e378e810f3bafbaf2732f9d87 (diff)
arm64: kernel: fix __cpu_suspend mm switch on warm-boot
commit f43c27188a49111b58e9611afa2f0365b0b55625 upstream. On arm64 the TTBR0_EL1 register is set to either the reserved TTBR0 page tables on boot or to the active_mm mappings belonging to user space processes, it must never be set to swapper_pg_dir page tables mappings. When a CPU is booted its active_mm is set to init_mm even though its TTBR0_EL1 points at the reserved TTBR0 page mappings. This implies that when __cpu_suspend is triggered the active_mm can point at init_mm even if the current TTBR0_EL1 register contains the reserved TTBR0_EL1 mappings. Therefore, the mm save and restore executed in __cpu_suspend might turn out to be erroneous in that, if the current->active_mm corresponds to init_mm, on resume from low power it ends up restoring in the TTBR0_EL1 the init_mm mappings that are global and can cause speculation of TLB entries which end up being propagated to user space. This patch fixes the issue by checking the active_mm pointer before restoring the TTBR0 mappings. If the current active_mm == &init_mm, the code sets the TTBR0_EL1 to the reserved TTBR0 mapping instead of switching back to the active_mm, which is the expected behaviour corresponding to the TTBR0_EL1 settings when __cpu_suspend was entered. Fixes: 95322526ef62 ("arm64: kernel: cpu_{suspend/resume} implementation") Cc: Will Deacon <will.deacon@arm.com> Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
1 files changed, 13 insertions, 1 deletions
diff --git a/arch/arm64/kernel/suspend.c b/arch/arm64/kernel/suspend.c
index 3771b72b6569..2d6b6065fe7f 100644
--- a/arch/arm64/kernel/suspend.c
+++ b/arch/arm64/kernel/suspend.c
@@ -5,6 +5,7 @@
#include <asm/debug-monitors.h>
#include <asm/pgtable.h>
#include <asm/memory.h>
+#include <asm/mmu_context.h>
#include <asm/smp_plat.h>
#include <asm/suspend.h>
#include <asm/tlbflush.h>
@@ -98,7 +99,18 @@ int __cpu_suspend(unsigned long arg, int (*fn)(unsigned long))
ret = __cpu_suspend_enter(arg, fn);
if (ret == 0) {
- cpu_switch_mm(mm->pgd, mm);
+ /*
+ * We are resuming from reset with TTBR0_EL1 set to the
+ * idmap to enable the MMU; restore the active_mm mappings in
+ * TTBR0_EL1 unless the active_mm == &init_mm, in which case
+ * the thread entered __cpu_suspend with TTBR0_EL1 set to
+ * reserved TTBR0 page tables and should be restored as such.
+ */
+ if (mm == &init_mm)
+ cpu_set_reserved_ttbr0();
+ else
+ cpu_switch_mm(mm->pgd, mm);