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>

arch/powerpc/include/asm/system.h

@@ -112,8 +112,13 @@ static inline int debugger_fault_handler(struct pt_regs *regs) { return 0; }
 #endif
 
 extern int set_dabr(unsigned long dabr);
+#ifdef CONFIG_PPC_ADV_DEBUG_REGS
+extern void do_send_trap(struct pt_regs *regs, unsigned long address,
+			 unsigned long error_code, int signal_code, int brkpt);
+#else
 extern void do_dabr(struct pt_regs *regs, unsigned long address,
 		    unsigned long error_code);
+#endif
 extern void print_backtrace(unsigned long *);
 extern void show_regs(struct pt_regs * regs);
 extern void flush_instruction_cache(void);

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

arch/powerpc/kernel/signal.c

@@ -140,17 +140,15 @@ static int do_signal_pending(sigset_t *oldset, struct pt_regs *regs)
 		return 0;               /* no signals delivered */
 	}
 
+#ifndef CONFIG_PPC_ADV_DEBUG_REGS
         /*
 	 * Reenable the DABR before delivering the signal to
 	 * user space. The DABR will have been cleared if it
 	 * triggered inside the kernel.
 	 */
-	if (current->thread.dabr) {
+	if (current->thread.dabr)
 		set_dabr(current->thread.dabr);
-#ifdef CONFIG_PPC_ADV_DEBUG_REGS
-		mtspr(SPRN_DBCR0, current->thread.dbcr0);
 #endif
-	}
 
 	if (is32) {
         	if (ka.sa.sa_flags & SA_SIGINFO)

arch/powerpc/kernel/signal_32.c

@@ -1092,8 +1092,12 @@ int sys_debug_setcontext(struct ucontext __user *ctx,
 				new_msr |= MSR_DE;
 				new_dbcr0 |= (DBCR0_IDM | DBCR0_IC);
 			} else {
-				new_msr &= ~MSR_DE;
-				new_dbcr0 &= ~(DBCR0_IDM | DBCR0_IC);
+				new_dbcr0 &= ~DBCR0_IC;
+				if (!DBCR_ACTIVE_EVENTS(new_dbcr0,
+						current->thread.dbcr1)) {
+					new_msr &= ~MSR_DE;
+					new_dbcr0 &= ~DBCR0_IDM;
+				}
 			}
 #else
 			if (op.dbg_value)

arch/powerpc/kernel/traps.c

@@ -1034,9 +1034,68 @@ void SoftwareEmulation(struct pt_regs *regs)
 #endif /* CONFIG_8xx */
 
 #ifdef CONFIG_PPC_ADV_DEBUG_REGS
+static void handle_debug(struct pt_regs *regs, unsigned long debug_status)
+{
+	int changed = 0;
+	/*
+	 * Determine the cause of the debug event, clear the
+	 * event flags and send a trap to the handler. Torez
+	 */
+	if (debug_status & (DBSR_DAC1R | DBSR_DAC1W)) {
+		dbcr_dac(current) &= ~(DBCR_DAC1R | DBCR_DAC1W);
+#ifdef CONFIG_PPC_ADV_DEBUG_DAC_RANGE
+		current->thread.dbcr2 &= ~DBCR2_DAC12MODE;
+#endif
+		do_send_trap(regs, mfspr(SPRN_DAC1), debug_status, TRAP_HWBKPT,
+			     5);
+		changed |= 0x01;
+	}  else if (debug_status & (DBSR_DAC2R | DBSR_DAC2W)) {
+		dbcr_dac(current) &= ~(DBCR_DAC2R | DBCR_DAC2W);
+		do_send_trap(regs, mfspr(SPRN_DAC2), debug_status, TRAP_HWBKPT,
+			     6);
+		changed |= 0x01;
+	}  else if (debug_status & DBSR_IAC1) {
+		current->thread.dbcr0 &= ~DBCR0_IAC1;
+		dbcr_iac_range(current) &= ~DBCR_IAC12MODE;
+		do_send_trap(regs, mfspr(SPRN_IAC1), debug_status, TRAP_HWBKPT,
+			     1);
+		changed |= 0x01;
+	}  else if (debug_status & DBSR_IAC2) {
+		current->thread.dbcr0 &= ~DBCR0_IAC2;
+		do_send_trap(regs, mfspr(SPRN_IAC2), debug_status, TRAP_HWBKPT,
+			     2);
+		changed |= 0x01;
+	}  else if (debug_status & DBSR_IAC3) {
+		current->thread.dbcr0 &= ~DBCR0_IAC3;
+		dbcr_iac_range(current) &= ~DBCR_IAC34MODE;
+		do_send_trap(regs, mfspr(SPRN_IAC3), debug_status, TRAP_HWBKPT,
+			     3);
+		changed |= 0x01;
+	}  else if (debug_status & DBSR_IAC4) {
+		current->thread.dbcr0 &= ~DBCR0_IAC4;
+		do_send_trap(regs, mfspr(SPRN_IAC4), debug_status, TRAP_HWBKPT,
+			     4);
+		changed |= 0x01;
+	}
+	/*
+	 * At the point this routine was called, the MSR(DE) was turned off.
+	 * Check all other debug flags and see if that bit needs to be turned
+	 * back on or not.
+	 */
+	if (DBCR_ACTIVE_EVENTS(current->thread.dbcr0, current->thread.dbcr1))
+		regs->msr |= MSR_DE;
+	else
+		/* Make sure the IDM flag is off */
+		current->thread.dbcr0 &= ~DBCR0_IDM;
+
+	if (changed & 0x01)
+		mtspr(SPRN_DBCR0, current->thread.dbcr0);
+}
 
 void __kprobes DebugException(struct pt_regs *regs, unsigned long debug_status)
 {
+	current->thread.dbsr = debug_status;
+
 	/* Hack alert: On BookE, Branch Taken stops on the branch itself, while
 	 * on server, it stops on the target of the branch. In order to simulate
 	 * the server behaviour, we thus restart right away with a single step
@@ -1080,27 +1139,21 @@ void __kprobes DebugException(struct pt_regs *regs, unsigned long debug_status)
 		if (debugger_sstep(regs))
 			return;
 
-		if (user_mode(regs))
-			current->thread.dbcr0 &= ~(DBCR0_IC);
-
-		_exception(SIGTRAP, regs, TRAP_TRACE, regs->nip);
-	} else if (debug_status & (DBSR_DAC1R | DBSR_DAC1W)) {
-		regs->msr &= ~MSR_DE;
-
 		if (user_mode(regs)) {
-			current->thread.dbcr0 &= ~(DBSR_DAC1R | DBSR_DAC1W |
-								DBCR0_IDM);
-		} else {
-			/* Disable DAC interupts */
-			mtspr(SPRN_DBCR0, mfspr(SPRN_DBCR0) & ~(DBSR_DAC1R |
-						DBSR_DAC1W | DBCR0_IDM));
-
-			/* Clear the DAC event */
-			mtspr(SPRN_DBSR, (DBSR_DAC1R | DBSR_DAC1W));
+			current->thread.dbcr0 &= ~DBCR0_IC;
+#ifdef CONFIG_PPC_ADV_DEBUG_REGS
+			if (DBCR_ACTIVE_EVENTS(current->thread.dbcr0,
+					       current->thread.dbcr1))
+				regs->msr |= MSR_DE;
+			else
+				/* Make sure the IDM bit is off */
+				current->thread.dbcr0 &= ~DBCR0_IDM;
+#endif
 		}
-		/* Setup and send the trap to the handler */
-		do_dabr(regs, mfspr(SPRN_DAC1), debug_status);
-	}
+
+		_exception(SIGTRAP, regs, TRAP_TRACE, regs->nip);
+	} else
+		handle_debug(regs, debug_status);
 }
 #endif /* CONFIG_PPC_ADV_DEBUG_REGS */