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authorWill Deacon <will.deacon@arm.com>2015-03-19 15:43:00 +0000
committerCatalin Marinas <catalin.marinas@arm.com>2015-03-20 17:05:16 +0000
commit130c93fd10c4d150e39d8879420c1351aa207fa9 (patch)
tree6957d65f53549713852ce1f18af6c3600ec8c8a9
parent06e5801b8cb3fc057d88cb4dc03c0b64b2744cda (diff)
downloadlwn-130c93fd10c4d150e39d8879420c1351aa207fa9.tar.gz
lwn-130c93fd10c4d150e39d8879420c1351aa207fa9.zip
arm64: efi: don't restore TTBR0 if active_mm points at init_mm
init_mm isn't a normal mm: it has swapper_pg_dir as its pgd (which contains kernel mappings) and is used as the active_mm for the idle thread. When restoring the pgd after an EFI call, we write current->active_mm into TTBR0. If the current task is actually the idle thread (e.g. when initialising the EFI RTC before entering userspace), then the TLB can erroneously populate itself with junk global entries as a result of speculative table walks. When we do eventually return to userspace, the task can end up hitting these junk mappings leading to lockups, corruption or crashes. This patch fixes the problem in the same way as the CPU suspend code by ensuring that we never switch to the init_mm in efi_set_pgd and instead point TTBR0 at the zero page. A check is also added to cpu_switch_mm to BUG if we get passed swapper_pg_dir. Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Fixes: f3cdfd239da5 ("arm64/efi: move SetVirtualAddressMap() to UEFI stub") Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
-rw-r--r--arch/arm64/include/asm/proc-fns.h6
-rw-r--r--arch/arm64/kernel/efi.c6
2 files changed, 10 insertions, 2 deletions
diff --git a/arch/arm64/include/asm/proc-fns.h b/arch/arm64/include/asm/proc-fns.h
index 9a8fd84f8fb2..941c375616e2 100644
--- a/arch/arm64/include/asm/proc-fns.h
+++ b/arch/arm64/include/asm/proc-fns.h
@@ -39,7 +39,11 @@ extern u64 cpu_do_resume(phys_addr_t ptr, u64 idmap_ttbr);
#include <asm/memory.h>
-#define cpu_switch_mm(pgd,mm) cpu_do_switch_mm(virt_to_phys(pgd),mm)
+#define cpu_switch_mm(pgd,mm) \
+do { \
+ BUG_ON(pgd == swapper_pg_dir); \
+ cpu_do_switch_mm(virt_to_phys(pgd),mm); \
+} while (0)
#define cpu_get_pgd() \
({ \
diff --git a/arch/arm64/kernel/efi.c b/arch/arm64/kernel/efi.c
index 2b8d70164428..ab21e0d58278 100644
--- a/arch/arm64/kernel/efi.c
+++ b/arch/arm64/kernel/efi.c
@@ -337,7 +337,11 @@ core_initcall(arm64_dmi_init);
static void efi_set_pgd(struct mm_struct *mm)
{
- cpu_switch_mm(mm->pgd, mm);
+ if (mm == &init_mm)
+ cpu_set_reserved_ttbr0();
+ else
+ cpu_switch_mm(mm->pgd, mm);
+
flush_tlb_all();
if (icache_is_aivivt())
__flush_icache_all();