[AVR32] Enable debugging only when needed

Keep track of processes being debugged (including the kernel itself)
and turn the OCD system on and off as appropriate. Since enabling
debugging turns off some optimizations in the CPU core, this fixes the
issue that enabling KProbes support or simply running a program under
gdbserver will reduce system performance significantly until the next
reboot.

The CPU performance will still be reduced for all processes while a
process is being debugged, but this is a lot better than reducing the
performance forever.

Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>

1 files changed, 2 insertions, 3 deletions

diff --git a/arch/avr32/kernel/kprobes.c b/arch/avr32/kernel/kprobes.c
index 799ba89b07a8..f820e9f25520 100644
--- a/arch/avr32/kernel/kprobes.c
+++ b/arch/avr32/kernel/kprobes.c
@@ -48,6 +48,7 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p)
 void __kprobes arch_arm_kprobe(struct kprobe *p)
 {
         pr_debug("arming kprobe at %p\n", p->addr);
+        ocd_enable(NULL);
         *p->addr = BREAKPOINT_INSTRUCTION;
         flush_icache_range((unsigned long)p->addr,
                            (unsigned long)p->addr + sizeof(kprobe_opcode_t));
@@ -56,6 +57,7 @@ void __kprobes arch_arm_kprobe(struct kprobe *p)
 void __kprobes arch_disarm_kprobe(struct kprobe *p)
 {
         pr_debug("disarming kprobe at %p\n", p->addr);
+        ocd_disable(NULL);
         *p->addr = p->opcode;
         flush_icache_range((unsigned long)p->addr,
                            (unsigned long)p->addr + sizeof(kprobe_opcode_t));
@@ -260,9 +262,6 @@ int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 
 int __init arch_init_kprobes(void)
 {
-        printk("KPROBES: Enabling monitor mode (MM|DBE)...\n");
-        ocd_write(DC, (1 << OCD_DC_MM_BIT) | (1 << OCD_DC_DBE_BIT));
-
         /* TODO: Register kretprobe trampoline */
         return 0;
 }