powerpc/booke: Add support for advanced debug registers

powerpc/booke: Add support for advanced debug registers

From: Dave Kleikamp <shaggy@linux.vnet.ibm.com>

Based on patches originally written by Torez Smith.

This patch defines context switch and trap related functionality
for BookE specific Debug Registers. It adds support to ptrace()
for setting and getting BookE related Debug Registers

Signed-off-by: Dave Kleikamp <shaggy@linux.vnet.ibm.com>
Cc: Torez Smith  <lnxtorez@linux.vnet.ibm.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: David Gibson <dwg@au1.ibm.com>
Cc: Josh Boyer <jwboyer@linux.vnet.ibm.com>
Cc: Kumar Gala <galak@kernel.crashing.org>
Cc: Sergio Durigan Junior <sergiodj@br.ibm.com>
Cc: Thiago Jung Bauermann <bauerman@br.ibm.com>
Cc: linuxppc-dev list <Linuxppc-dev@ozlabs.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 93 insertions, 17 deletions

diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 9be77e3936fb..e4d71ced97ef 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -245,6 +245,24 @@ void discard_lazy_cpu_state(void)
 }
 #endif /* CONFIG_SMP */
 
+#ifdef CONFIG_PPC_ADV_DEBUG_REGS
+void do_send_trap(struct pt_regs *regs, unsigned long address,
+		  unsigned long error_code, int signal_code, int breakpt)
+{
+	siginfo_t info;
+
+	if (notify_die(DIE_DABR_MATCH, "dabr_match", regs, error_code,
+			11, SIGSEGV) == NOTIFY_STOP)
+		return;
+
+	/* Deliver the signal to userspace */
+	info.si_signo = SIGTRAP;
+	info.si_errno = breakpt;	/* breakpoint or watchpoint id */
+	info.si_code = signal_code;
+	info.si_addr = (void __user *)address;
+	force_sig_info(SIGTRAP, &info, current);
+}
+#else	/* !CONFIG_PPC_ADV_DEBUG_REGS */
 void do_dabr(struct pt_regs *regs, unsigned long address,
 		    unsigned long error_code)
 {
@@ -257,12 +275,6 @@ void do_dabr(struct pt_regs *regs, unsigned long address,
 	if (debugger_dabr_match(regs))
 		return;
 
-	/* Clear the DAC and struct entries.  One shot trigger */
-#ifdef CONFIG_PPC_ADV_DEBUG_REGS
-	mtspr(SPRN_DBCR0, mfspr(SPRN_DBCR0) & ~(DBSR_DAC1R | DBSR_DAC1W
-							| DBCR0_IDM));
-#endif
-
 	/* Clear the DABR */
 	set_dabr(0);
 
@@ -273,9 +285,82 @@ void do_dabr(struct pt_regs *regs, unsigned long address,
 	info.si_addr = (void __user *)address;
 	force_sig_info(SIGTRAP, &info, current);
 }
+#endif	/* CONFIG_PPC_ADV_DEBUG_REGS */
 
 static DEFINE_PER_CPU(unsigned long, current_dabr);
 
+#ifdef CONFIG_PPC_ADV_DEBUG_REGS
+/*
+ * Set the debug registers back to their default "safe" values.
+ */
+static void set_debug_reg_defaults(struct thread_struct *thread)
+{
+	thread->iac1 = thread->iac2 = 0;
+#if CONFIG_PPC_ADV_DEBUG_IACS > 2
+	thread->iac3 = thread->iac4 = 0;
+#endif
+	thread->dac1 = thread->dac2 = 0;
+#if CONFIG_PPC_ADV_DEBUG_DVCS > 0
+	thread->dvc1 = thread->dvc2 = 0;
+#endif
+	thread->dbcr0 = 0;
+#ifdef CONFIG_BOOKE
+	/*
+	 * Force User/Supervisor bits to b11 (user-only MSR[PR]=1)
+	 */
+	thread->dbcr1 = DBCR1_IAC1US | DBCR1_IAC2US |	\
+			DBCR1_IAC3US | DBCR1_IAC4US;
+	/*
+	 * Force Data Address Compare User/Supervisor bits to be User-only
+	 * (0b11 MSR[PR]=1) and set all other bits in DBCR2 register to be 0.
+	 */
+	thread->dbcr2 = DBCR2_DAC1US | DBCR2_DAC2US;
+#else
+	thread->dbcr1 = 0;
+#endif
+}
+
+static void prime_debug_regs(struct thread_struct *thread)
+{
+	mtspr(SPRN_IAC1, thread->iac1);
+	mtspr(SPRN_IAC2, thread->iac2);
+#if CONFIG_PPC_ADV_DEBUG_IACS > 2
+	mtspr(SPRN_IAC3, thread->iac3);
+	mtspr(SPRN_IAC4, thread->iac4);
+#endif
+	mtspr(SPRN_DAC1, thread->dac1);
+	mtspr(SPRN_DAC2, thread->dac2);
+#if CONFIG_PPC_ADV_DEBUG_DVCS > 0
+	mtspr(SPRN_DVC1, thread->dvc1);
+	mtspr(SPRN_DVC2, thread->dvc2);
+#endif
+	mtspr(SPRN_DBCR0, thread->dbcr0);
+	mtspr(SPRN_DBCR1, thread->dbcr1);
+#ifdef CONFIG_BOOKE
+	mtspr(SPRN_DBCR2, thread->dbcr2);
+#endif
+}
+/*
+ * Unless neither the old or new thread are making use of the
+ * debug registers, set the debug registers from the values
+ * stored in the new thread.
+ */
+static void switch_booke_debug_regs(struct thread_struct *new_thread)
+{
+	if ((current->thread.dbcr0 & DBCR0_IDM)
+		|| (new_thread->dbcr0 & DBCR0_IDM))
+			prime_debug_regs(new_thread);
+}
+#else	/* !CONFIG_PPC_ADV_DEBUG_REGS */
+static void set_debug_reg_defaults(struct thread_struct *thread)
+{
+	if (thread->dabr) {
+		thread->dabr = 0;
+		set_dabr(0);
+	}
+}
+#endif	/* CONFIG_PPC_ADV_DEBUG_REGS */
+
 int set_dabr(unsigned long dabr)
 {
 	__get_cpu_var(current_dabr) = dabr;
@@ -372,9 +457,7 @@ struct task_struct *__switch_to(struct task_struct *prev,
 #endif /* CONFIG_SMP */
 
 #ifdef CONFIG_PPC_ADV_DEBUG_REGS
-	/* If new thread DAC (HW breakpoint) is the same then leave it */
-	if (new->thread.dabr)
-		set_dabr(new->thread.dabr);
+	switch_booke_debug_regs(&new->thread);
 #else
 	if (unlikely(__get_cpu_var(current_dabr) != new->thread.dabr))
 		set_dabr(new->thread.dabr);
@@ -556,14 +639,7 @@ void flush_thread(void)
 {
 	discard_lazy_cpu_state();
 
-	if (current->thread.dabr) {
-		current->thread.dabr = 0;
-		set_dabr(0);
-
-#ifdef CONFIG_PPC_ADV_DEBUG_REGS
-		current->thread.dbcr0 &= ~(DBSR_DAC1R | DBSR_DAC1W);
-#endif
-	}
+	set_debug_reg_defaults(&current->thread);
 }
 
 void