Subject: Re: [RFC] 4xx hardware watchpoint support

From: Luis Machado <[email-masked]>
Date: Wed, 23 Jul 2008 13:10:41 -0300

On Wed, 2008-07-23 at 11:53 -0400, Josh Boyer wrote:
> Shouldn't this (and other places) be:
> 
> #if defined(CONFIG_44x) || defined(CONFIG_BOOKE)
> 
> if you are going to exclude 40x for now?  Otherwise this is still
> enabled on 405 and setting the wrong register.
> 
> josh

Yes, sorry. I wasn't aware of this specific define value. It makes
things easier to support 405's later.

Like so?

This addresses Christoph's comments as well.

Signed-off-by: Luis Machado <[email-masked]>

Index: linux-2.6.26/arch/powerpc/kernel/entry_32.S
===================================================================
--- linux-2.6.26.orig/arch/powerpc/kernel/entry_32.S	2008-07-23 07:44:57.000000000 -0700
+++ linux-2.6.26/arch/powerpc/kernel/entry_32.S	2008-07-23 07:50:31.000000000 -0700
@@ -148,7 +148,7 @@
 	/* Check to see if the dbcr0 register is set up to debug.  Use the
 	   internal debug mode bit to do this. */
 	lwz	r12,THREAD_DBCR0(r12)
-	andis.	r12,r12,DBCR0_IDM@h
+	andis.	r12,r12,(DBCR0_IDM  | DBSR_DAC1R | DBSR_DAC1W)@h
 	beq+	3f
 	/* From user and task is ptraced - load up global dbcr0 */
 	li	r12,-1			/* clear all pending debug events */
@@ -292,7 +292,7 @@
 	/* If the process has its own DBCR0 value, load it up.  The internal
 	   debug mode bit tells us that dbcr0 should be loaded. */
 	lwz	r0,THREAD+THREAD_DBCR0(r2)
-	andis.	r10,r0,DBCR0_IDM@h
+	andis.	r10,r0,(DBCR0_IDM  | DBSR_DAC1R | DBSR_DAC1W)@h
 	bnel-	load_dbcr0
 #endif
 #ifdef CONFIG_44x
@@ -720,7 +720,7 @@
 	/* Check whether this process has its own DBCR0 value.  The internal
 	   debug mode bit tells us that dbcr0 should be loaded. */
 	lwz	r0,THREAD+THREAD_DBCR0(r2)
-	andis.	r10,r0,DBCR0_IDM@h
+	andis.	r10,r0,(DBCR0_IDM  | DBSR_DAC1R | DBSR_DAC1W)@h
 	bnel-	load_dbcr0
 #endif
 
Index: linux-2.6.26/arch/powerpc/kernel/process.c
===================================================================
--- linux-2.6.26.orig/arch/powerpc/kernel/process.c	2008-07-23 07:44:57.000000000 -0700
+++ linux-2.6.26/arch/powerpc/kernel/process.c	2008-07-23 07:50:31.000000000 -0700
@@ -47,6 +47,8 @@
 #ifdef CONFIG_PPC64
 #include <asm/firmware.h>
 #endif
+#include <linux/kprobes.h>
+#include <linux/kdebug.h>
 
 extern unsigned long _get_SP(void);
 
@@ -239,6 +241,35 @@
 }
 #endif /* CONFIG_SMP */
 
+void do_dabr(struct pt_regs *regs, unsigned long address,
+		    unsigned long error_code)
+{
+	siginfo_t info;
+
+	if (notify_die(DIE_DABR_MATCH, "dabr_match", regs, error_code,
+			11, SIGSEGV) == NOTIFY_STOP)
+		return;
+
+	if (debugger_dabr_match(regs))
+		return;
+
+	/* Clear the DAC and struct entries.  One shot trigger */
+#if (defined(CONFIG_44x) || defined(CONFIG_BOOKE))
+	mtspr(SPRN_DBCR0, mfspr(SPRN_DBCR0) & ~(DBSR_DAC1R | DBSR_DAC1W
+							| DBCR0_IDM));
+#endif
+
+	/* Clear the DABR */
+	set_dabr(0);
+
+	/* Deliver the signal to userspace */
+	info.si_signo = SIGTRAP;
+	info.si_errno = 0;
+	info.si_code = TRAP_HWBKPT;
+	info.si_addr = (void __user *)address;
+	force_sig_info(SIGTRAP, &info, current);
+}
+
 static DEFINE_PER_CPU(unsigned long, current_dabr);
 
 int set_dabr(unsigned long dabr)
@@ -254,6 +285,11 @@
 #if defined(CONFIG_PPC64) || defined(CONFIG_6xx)
 	mtspr(SPRN_DABR, dabr);
 #endif
+
+#if defined(CONFIG_44x) || defined(CONFIG_BOOKE)
+	mtspr(SPRN_DAC1, dabr);
+#endif
+
 	return 0;
 }
 
@@ -337,6 +373,12 @@
 	if (unlikely(__get_cpu_var(current_dabr) != new->thread.dabr))
 		set_dabr(new->thread.dabr);
 
+#if defined(CONFIG_44x) || defined(CONFIG_BOOKE)
+	/* If new thread DAC (HW breakpoint) is the same then leave it */
+	if (new->thread.dabr)
+		set_dabr(new->thread.dabr);
+#endif
+
 	new_thread = &new->thread;
 	old_thread = &current->thread;
 
@@ -525,6 +567,10 @@
 	if (current->thread.dabr) {
 		current->thread.dabr = 0;
 		set_dabr(0);
+
+#if defined(CONFIG_44x) || defined(CONFIG_BOOKE)
+		current->thread.dbcr0 &= ~(DBSR_DAC1R | DBSR_DAC1W);
+#endif
 	}
 }
 
Index: linux-2.6.26/arch/powerpc/kernel/ptrace.c
===================================================================
--- linux-2.6.26.orig/arch/powerpc/kernel/ptrace.c	2008-07-23 07:44:57.000000000 -0700
+++ linux-2.6.26/arch/powerpc/kernel/ptrace.c	2008-07-23 07:53:45.000000000 -0700
@@ -703,7 +703,7 @@
 
 	if (regs != NULL) {
 #if defined(CONFIG_40x) || defined(CONFIG_BOOKE)
-		task->thread.dbcr0 = DBCR0_IDM | DBCR0_IC;
+		task->thread.dbcr0 |= DBCR0_IDM | DBCR0_IC;
 		regs->msr |= MSR_DE;
 #else
 		regs->msr |= MSR_SE;
@@ -716,9 +716,16 @@
 {
 	struct pt_regs *regs = task->thread.regs;
 
+
+#if defined(CONFIG_44x) || defined(CONFIG_BOOKE)
+	/* If DAC then do not single step, skip */
+	if (task->thread.dabr)
+		return;
+#endif
+
 	if (regs != NULL) {
 #if defined(CONFIG_40x) || defined(CONFIG_BOOKE)
-		task->thread.dbcr0 = 0;
+		task->thread.dbcr0 &= ~(DBCR0_IC | DBCR0_IDM);
 		regs->msr &= ~MSR_DE;
 #else
 		regs->msr &= ~MSR_SE;
@@ -727,22 +734,75 @@
 	clear_tsk_thread_flag(task, TIF_SINGLESTEP);
 }
 
-static int ptrace_set_debugreg(struct task_struct *task, unsigned long addr,
+int ptrace_set_debugreg(struct task_struct *task, unsigned long addr,
 			       unsigned long data)
 {
-	/* We only support one DABR and no IABRS at the moment */
+	/* For ppc64 we support one DABR and no IABR's at the moment (ppc64).
+	 *  For embedded processors we support one DAC and no IAC's at the
+	 *  moment.
+	 */
 	if (addr > 0)
 		return -EINVAL;
 
-	/* The bottom 3 bits are flags */
 	if ((data & ~0x7UL) >= TASK_SIZE)
 		return -EIO;
 
-	/* Ensure translation is on */
+#ifdef CONFIG_PPC64
+
+	/* For processors using DABR (i.e. 970), the bottom 3 bits are flags.
+	 *  It was assumed, on previous implementations, that 3 bits were
+	 *  passed together with the data address, fitting the design of the
+	 *  DABR register, as follows:
+	 *
+	 *  bit 0: Read flag
+	 *  bit 1: Write flag
+	 *  bit 2: Breakpoint translation
+	 *
+	 *  Thus, we use them here as so.
+	 */
+
+	/* Ensure breakpoint translation bit is set */
 	if (data && !(data & DABR_TRANSLATION))
 		return -EIO;
 
+	/* Move contents to the DABR register */
 	task->thread.dabr = data;
+
+#endif
+#if defined(CONFIG_44x) || defined(CONFIG_BOOKE)
+
+	/* As described above, it was assumed 3 bits were passed with the data
+	 *  address, but we will assume only the mode bits will be passed
+	 *  as to not cause alignment restrictions for DAC-based processors.
+	 */
+
+	/* DAC's hold the whole address without any mode flags */
+	task->thread.dabr = data & ~0x3UL;
+
+	if (task->thread.dabr == 0) {
+		task->thread.dbcr0 &= ~(DBSR_DAC1R | DBSR_DAC1W | DBCR0_IDM);
+		task->thread.regs->msr &= ~MSR_DE;
+		return 0;
+	}
+
+	/* Read or Write bits must be set */
+
+	if (!(data & 0x3UL))
+		return -EINVAL;
+
+	/* Set the Internal Debugging flag (IDM bit 1) for the DBCR0
+	   register */
+	task->thread.dbcr0 = DBCR0_IDM;
+
+	/* Check for write and read flags and set DBCR0
+	   accordingly */
+	if (data & 0x1UL)
+		task->thread.dbcr0 |= DBSR_DAC1R;
+	if (data & 0x2UL)
+		task->thread.dbcr0 |= DBSR_DAC1W;
+
+	task->thread.regs->msr |= MSR_DE;
+#endif
 	return 0;
 }
 
Index: linux-2.6.26/arch/powerpc/kernel/signal.c
===================================================================
--- linux-2.6.26.orig/arch/powerpc/kernel/signal.c	2008-07-23 07:44:57.000000000 -0700
+++ linux-2.6.26/arch/powerpc/kernel/signal.c	2008-07-23 07:50:31.000000000 -0700
@@ -145,8 +145,12 @@
 	 * 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);
+#if defined(CONFIG_44x) || defined(CONFIG_BOOKE)
+		mtspr(SPRN_DBCR0, current->thread.dbcr0);
+#endif
+	}
 
 	if (is32) {
         	if (ka.sa.sa_flags & SA_SIGINFO)
Index: linux-2.6.26/arch/powerpc/kernel/traps.c
===================================================================
--- linux-2.6.26.orig/arch/powerpc/kernel/traps.c	2008-07-23 07:44:57.000000000 -0700
+++ linux-2.6.26/arch/powerpc/kernel/traps.c	2008-07-23 07:50:31.000000000 -0700
@@ -1067,6 +1067,22 @@
 		}
 
 		_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));
+		}
+		/* Setup and send the trap to the handler */
+		do_dabr(regs, mfspr(SPRN_DAC1), debug_status);
 	}
 }
 #endif /* CONFIG_4xx || CONFIG_BOOKE */
Index: linux-2.6.26/arch/powerpc/mm/fault.c
===================================================================
--- linux-2.6.26.orig/arch/powerpc/mm/fault.c	2008-07-23 07:44:57.000000000 -0700
+++ linux-2.6.26/arch/powerpc/mm/fault.c	2008-07-23 07:50:31.000000000 -0700
@@ -100,31 +100,6 @@
 	return 0;
 }
 
-#if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE))
-static void do_dabr(struct pt_regs *regs, unsigned long address,
-		    unsigned long error_code)
-{
-	siginfo_t info;
-
-	if (notify_die(DIE_DABR_MATCH, "dabr_match", regs, error_code,
-			11, SIGSEGV) == NOTIFY_STOP)
-		return;
-
-	if (debugger_dabr_match(regs))
-		return;
-
-	/* Clear the DABR */
-	set_dabr(0);
-
-	/* Deliver the signal to userspace */
-	info.si_signo = SIGTRAP;
-	info.si_errno = 0;
-	info.si_code = TRAP_HWBKPT;
-	info.si_addr = (void __user *)address;
-	force_sig_info(SIGTRAP, &info, current);
-}
-#endif /* !(CONFIG_4xx || CONFIG_BOOKE)*/
-
 /*
  * For 600- and 800-family processors, the error_code parameter is DSISR
  * for a data fault, SRR1 for an instruction fault. For 400-family processors
Index: linux-2.6.26/include/asm-powerpc/system.h
===================================================================
--- linux-2.6.26.orig/include/asm-powerpc/system.h	2008-07-23 07:44:57.000000000 -0700
+++ linux-2.6.26/include/asm-powerpc/system.h	2008-07-23 07:50:31.000000000 -0700
@@ -110,6 +110,8 @@
 #endif
 
 extern int set_dabr(unsigned long dabr);
+extern void do_dabr(struct pt_regs *regs, unsigned long address,
+		    unsigned long error_code);
 extern void print_backtrace(unsigned long *);
 extern void show_regs(struct pt_regs * regs);
 extern void flush_instruction_cache(void);