This is a note to let you know that I've just added the patch titled
arm64: debug: clear mdscr_el1 instead of taking the OS lock
to the 3.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
arm64-debug-clear-mdscr_el1-instead-of-taking-the-os-lock.patch
and it can be found in the queue-3.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 9c413e25d95fd3c0abe23eadad66191b22baa549 Mon Sep 17 00:00:00 2001
From: Will Deacon <will.deacon@xxxxxxx>
Date: Wed, 8 May 2013 17:01:12 +0100
Subject: arm64: debug: clear mdscr_el1 instead of taking the OS lock
From: Will Deacon <will.deacon@xxxxxxx>
commit 9c413e25d95fd3c0abe23eadad66191b22baa549 upstream.
During boot, we take the debug OS lock before interrupts are enabled.
This is required to prevent clearing of PSTATE.D on the interrupt entry
path, which could result in spurious debug exceptions before we've got
round to resetting things like the hardware breakpoints registers to a
sane state.
A problem with this approach is that taking the OS lock prevents an
external JTAG debugger from debugging the system, which is especially
irritating during boot, where JTAG debugging can be most useful.
This patch clears mdscr_el1 rather than taking the lock, clearing the
MDE and KDE bits and preventing self-hosted hardware debug exceptions
from occurring.
Tested-by: Mark Rutland <mark.rutland@xxxxxxx>
Signed-off-by: Will Deacon <will.deacon@xxxxxxx>
Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/arm64/kernel/debug-monitors.c | 2 --
arch/arm64/mm/proc.S | 3 +--
2 files changed, 1 insertion(+), 4 deletions(-)
--- a/arch/arm64/kernel/debug-monitors.c
+++ b/arch/arm64/kernel/debug-monitors.c
@@ -136,8 +136,6 @@ void disable_debug_monitors(enum debug_e
*/
static void clear_os_lock(void *unused)
{
- asm volatile("msr mdscr_el1, %0" : : "r" (0));
- isb();
asm volatile("msr oslar_el1, %0" : : "r" (0));
isb();
}
--- a/arch/arm64/mm/proc.S
+++ b/arch/arm64/mm/proc.S
@@ -119,8 +119,7 @@ ENTRY(__cpu_setup)
mov x0, #3 << 20
msr cpacr_el1, x0 // Enable FP/ASIMD
- mov x0, #1
- msr oslar_el1, x0 // Set the debug OS lock
+ msr mdscr_el1, xzr // Reset mdscr_el1
tlbi vmalle1is // invalidate I + D TLBs
/*
* Memory region attributes for LPAE:
Patches currently in stable-queue which might be from will.deacon@xxxxxxx are
queue-3.9/arm64-debug-clear-mdscr_el1-instead-of-taking-the-os-lock.patch
--
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