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authorWill Deacon <will.deacon@arm.com>2013-05-08 17:01:12 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-05-24 11:35:46 -0700
commit71b86dfc5ed5a27c6d02eff2957587b8a00ae3dd (patch)
tree2bb7451603645544fdc6554ed442fcafbb87a54d
parent4bb08696fab71294c8f1c134a21be9159f82ba08 (diff)
downloadvexpress-lsk-71b86dfc5ed5a27c6d02eff2957587b8a00ae3dd.tar.gz
arm64: debug: clear mdscr_el1 instead of taking the OS lock
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@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--arch/arm64/kernel/debug-monitors.c2
-rw-r--r--arch/arm64/mm/proc.S3
2 files changed, 1 insertions, 4 deletions
diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-monitors.c
index 0c3ba9f5137..f4726dc054b 100644
--- a/arch/arm64/kernel/debug-monitors.c
+++ b/arch/arm64/kernel/debug-monitors.c
@@ -136,8 +136,6 @@ void disable_debug_monitors(enum debug_el el)
*/
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();
}
diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S
index f1d8b9bbfda..a82ae886807 100644
--- 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: