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Subject[PATCH 4.7 072/143] arm64: kernel: Fix unmasked debug exceptions when restoring mdscr_el1
4.7-stable review patch.  If anyone has any objections, please let me know.


From: James Morse <>

commit 744c6c37cc18705d19e179622f927f5b781fe9cc upstream.

Changes to make the resume from cpu_suspend() code behave more like
secondary boot caused debug exceptions to be unmasked early by
__cpu_setup(). We then go on to restore mdscr_el1 in cpu_do_resume(),
potentially taking break or watch points based on uninitialised registers.

Mask debug exceptions in cpu_do_resume(), which is specific to resume
from cpu_suspend(). Debug exceptions will be restored to their original
state by local_dbg_restore() in cpu_suspend(), which runs after
hw_breakpoint_restore() has re-initialised the other registers.

Reported-by: Lorenzo Pieralisi <>
Fixes: cabe1c81ea5b ("arm64: Change cpu_resume() to enable mmu early then access sleep_sp by va")
Signed-off-by: James Morse <>
Acked-by: Will Deacon <>
Signed-off-by: Catalin Marinas <>
Signed-off-by: Greg Kroah-Hartman <>

arch/arm64/mm/proc.S | 9 +++++++++
1 file changed, 9 insertions(+)

--- a/arch/arm64/mm/proc.S
+++ b/arch/arm64/mm/proc.S
@@ -100,7 +100,16 @@ ENTRY(cpu_do_resume)

msr tcr_el1, x8
msr vbar_el1, x9
+ /*
+ * __cpu_setup() cleared MDSCR_EL1.MDE and friends, before unmasking
+ * debug exceptions. By restoring MDSCR_EL1 here, we may take a debug
+ * exception. Mask them until local_dbg_restore() in cpu_suspend()
+ * resets them.
+ */
+ disable_dbg
msr mdscr_el1, x10
msr sctlr_el1, x12
* Restore oslsr_el1 by writing oslar_el1

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