14 files changed, 358 insertions, 54 deletions

diff --git a/arch/mips/kernel/Makefile b/arch/mips/kernel/Makefile
index 25775cb..d9da711 100644
--- a/arch/mips/kernel/Makefile
+++ b/arch/mips/kernel/Makefile
@@ -6,7 +6,7 @@ extra-y		:= head.o init_task.o vmlinux.lds
 
 obj-y		+= cpu-probe.o branch.o entry.o genex.o irq.o process.o \
 		   ptrace.o reset.o setup.o signal.o syscall.o \
-		   time.o topology.o traps.o unaligned.o
+		   time.o topology.o traps.o unaligned.o watch.o
 
 obj-$(CONFIG_CEVT_BCM1480)	+= cevt-bcm1480.o
 obj-$(CONFIG_CEVT_R4K)		+= cevt-r4k.o
diff --git a/arch/mips/kernel/cpu-probe.c b/arch/mips/kernel/cpu-probe.c
index e621fda..0cf1545 100644
--- a/arch/mips/kernel/cpu-probe.c
+++ b/arch/mips/kernel/cpu-probe.c
@@ -21,6 +21,7 @@
 #include <asm/fpu.h>
 #include <asm/mipsregs.h>
 #include <asm/system.h>
+#include <asm/watch.h>
 
 /*
  * Not all of the MIPS CPUs have the "wait" instruction available. Moreover,
@@ -677,6 +678,7 @@ static inline void spram_config(void) {}
 static inline void cpu_probe_mips(struct cpuinfo_mips *c)
 {
 	decode_configs(c);
+	mips_probe_watch_registers(c);
 	switch (c->processor_id & 0xff00) {
 	case PRID_IMP_4KC:
 		c->cputype = CPU_4KC;
diff --git a/arch/mips/kernel/genex.S b/arch/mips/kernel/genex.S
index 01dcbe3..757d48f 100644
--- a/arch/mips/kernel/genex.S
+++ b/arch/mips/kernel/genex.S
@@ -453,7 +453,11 @@ NESTED(nmi_handler, PT_SIZE, sp)
 	BUILD_HANDLER tr tr sti silent			/* #13 */
 	BUILD_HANDLER fpe fpe fpe silent		/* #15 */
 	BUILD_HANDLER mdmx mdmx sti silent		/* #22 */
+#ifdef 	CONFIG_HARDWARE_WATCHPOINTS
+	BUILD_HANDLER watch watch sti silent		/* #23 */
+#else
 	BUILD_HANDLER watch watch sti verbose		/* #23 */
+#endif
 	BUILD_HANDLER mcheck mcheck cli verbose		/* #24 */
 	BUILD_HANDLER mt mt sti silent			/* #25 */
 	BUILD_HANDLER dsp dsp sti silent		/* #26 */
diff --git a/arch/mips/kernel/proc.c b/arch/mips/kernel/proc.c
index 36f0653..75bb130 100644
--- a/arch/mips/kernel/proc.c
+++ b/arch/mips/kernel/proc.c
@@ -23,6 +23,7 @@ static int show_cpuinfo(struct seq_file *m, void *v)
 	unsigned int version = cpu_data[n].processor_id;
 	unsigned int fp_vers = cpu_data[n].fpu_id;
 	char fmt [64];
+	int i;
 
 #ifdef CONFIG_SMP
 	if (!cpu_isset(n, cpu_online_map))
@@ -50,8 +51,16 @@ static int show_cpuinfo(struct seq_file *m, void *v)
 	seq_printf(m, "tlb_entries\t\t: %d\n", cpu_data[n].tlbsize);
 	seq_printf(m, "extra interrupt vector\t: %s\n",
 	              cpu_has_divec ? "yes" : "no");
-	seq_printf(m, "hardware watchpoint\t: %s\n",
-	              cpu_has_watch ? "yes" : "no");
+	seq_printf(m, "hardware watchpoint\t: %s",
+		   cpu_has_watch ? "yes, " : "no\n");
+	if (cpu_has_watch) {
+		seq_printf(m, "count: %d, address/irw mask: [",
+			   cpu_data[n].watch_reg_count);
+		for (i = 0; i < cpu_data[n].watch_reg_count; i++)
+			seq_printf(m, "%s0x%04x", i ? ", " : "" ,
+				   cpu_data[n].watch_reg_masks[i]);
+		seq_printf(m, "]\n");
+	}
 	seq_printf(m, "ASEs implemented\t:%s%s%s%s%s%s\n",
 		      cpu_has_mips16 ? " mips16" : "",
 		      cpu_has_mdmx ? " mdmx" : "",
diff --git a/arch/mips/kernel/process.c b/arch/mips/kernel/process.c
index 22fc19b..ca2e402 100644
--- a/arch/mips/kernel/process.c
+++ b/arch/mips/kernel/process.c
@@ -22,7 +22,6 @@
 #include <linux/personality.h>
 #include <linux/sys.h>
 #include <linux/user.h>
-#include <linux/a.out.h>
 #include <linux/init.h>
 #include <linux/completion.h>
 #include <linux/kallsyms.h>
diff --git a/arch/mips/kernel/ptrace.c b/arch/mips/kernel/ptrace.c
index 96ffc9c..054861c 100644
--- a/arch/mips/kernel/ptrace.c
+++ b/arch/mips/kernel/ptrace.c
@@ -46,7 +46,8 @@
  */
 void ptrace_disable(struct task_struct *child)
 {
-	/* Nothing to do.. */
+	/* Don't load the watchpoint registers for the ex-child. */
+	clear_tsk_thread_flag(child, TIF_LOAD_WATCH);
 }
 
 /*
@@ -167,6 +168,93 @@ int ptrace_setfpregs(struct task_struct *child, __u32 __user *data)
 	return 0;
 }
 
+int ptrace_get_watch_regs(struct task_struct *child,
+			  struct pt_watch_regs __user *addr)
+{
+	enum pt_watch_style style;
+	int i;
+
+	if (!cpu_has_watch || current_cpu_data.watch_reg_use_cnt == 0)
+		return -EIO;
+	if (!access_ok(VERIFY_WRITE, addr, sizeof(struct pt_watch_regs)))
+		return -EIO;
+
+#ifdef CONFIG_32BIT
+	style = pt_watch_style_mips32;
+#define WATCH_STYLE mips32
+#else
+	style = pt_watch_style_mips64;
+#define WATCH_STYLE mips64
+#endif
+
+	__put_user(style, &addr->style);
+	__put_user(current_cpu_data.watch_reg_use_cnt,
+		   &addr->WATCH_STYLE.num_valid);
+	for (i = 0; i < current_cpu_data.watch_reg_use_cnt; i++) {
+		__put_user(child->thread.watch.mips3264.watchlo[i],
+			   &addr->WATCH_STYLE.watchlo[i]);
+		__put_user(child->thread.watch.mips3264.watchhi[i] & 0xfff,
+			   &addr->WATCH_STYLE.watchhi[i]);
+		__put_user(current_cpu_data.watch_reg_masks[i],
+			   &addr->WATCH_STYLE.watch_masks[i]);
+	}
+	for (; i < 8; i++) {
+		__put_user(0, &addr->WATCH_STYLE.watchlo[i]);
+		__put_user(0, &addr->WATCH_STYLE.watchhi[i]);
+		__put_user(0, &addr->WATCH_STYLE.watch_masks[i]);
+	}
+
+	return 0;
+}
+
+int ptrace_set_watch_regs(struct task_struct *child,
+			  struct pt_watch_regs __user *addr)
+{
+	int i;
+	int watch_active = 0;
+	unsigned long lt[NUM_WATCH_REGS];
+	u16 ht[NUM_WATCH_REGS];
+
+	if (!cpu_has_watch || current_cpu_data.watch_reg_use_cnt == 0)
+		return -EIO;
+	if (!access_ok(VERIFY_READ, addr, sizeof(struct pt_watch_regs)))
+		return -EIO;
+	/* Check the values. */
+	for (i = 0; i < current_cpu_data.watch_reg_use_cnt; i++) {
+		__get_user(lt[i], &addr->WATCH_STYLE.watchlo[i]);
+#ifdef CONFIG_32BIT
+		if (lt[i] & __UA_LIMIT)
+			return -EINVAL;
+#else
+		if (test_tsk_thread_flag(child, TIF_32BIT_ADDR)) {
+			if (lt[i] & 0xffffffff80000000UL)
+				return -EINVAL;
+		} else {
+			if (lt[i] & __UA_LIMIT)
+				return -EINVAL;
+		}
+#endif
+		__get_user(ht[i], &addr->WATCH_STYLE.watchhi[i]);
+		if (ht[i] & ~0xff8)
+			return -EINVAL;
+	}
+	/* Install them. */
+	for (i = 0; i < current_cpu_data.watch_reg_use_cnt; i++) {
+		if (lt[i] & 7)
+			watch_active = 1;
+		child->thread.watch.mips3264.watchlo[i] = lt[i];
+		/* Set the G bit. */
+		child->thread.watch.mips3264.watchhi[i] = ht[i];
+	}
+
+	if (watch_active)
+		set_tsk_thread_flag(child, TIF_LOAD_WATCH);
+	else
+		clear_tsk_thread_flag(child, TIF_LOAD_WATCH);
+
+	return 0;
+}
+
 long arch_ptrace(struct task_struct *child, long request, long addr, long data)
 {
 	int ret;
@@ -440,6 +528,16 @@ long arch_ptrace(struct task_struct *child, long request, long addr, long data)
 				(unsigned long __user *) data);
 		break;
 
+	case PTRACE_GET_WATCH_REGS:
+		ret = ptrace_get_watch_regs(child,
+					(struct pt_watch_regs __user *) addr);
+		break;
+
+	case PTRACE_SET_WATCH_REGS:
+		ret = ptrace_set_watch_regs(child,
+					(struct pt_watch_regs __user *) addr);
+		break;
+
 	default:
 		ret = ptrace_request(child, request, addr, data);
 		break;
diff --git a/arch/mips/kernel/ptrace32.c b/arch/mips/kernel/ptrace32.c
index 76818be..1ca3410 100644
--- a/arch/mips/kernel/ptrace32.c
+++ b/arch/mips/kernel/ptrace32.c
@@ -15,6 +15,7 @@
  * binaries.
  */
 #include <linux/compiler.h>
+#include <linux/compat.h>
 #include <linux/kernel.h>
 #include <linux/sched.h>
 #include <linux/mm.h>
@@ -36,47 +37,17 @@
 #include <asm/uaccess.h>
 #include <asm/bootinfo.h>
 
-int ptrace_getregs(struct task_struct *child, __s64 __user *data);
-int ptrace_setregs(struct task_struct *child, __s64 __user *data);
-
-int ptrace_getfpregs(struct task_struct *child, __u32 __user *data);
-int ptrace_setfpregs(struct task_struct *child, __u32 __user *data);
-
 /*
  * Tracing a 32-bit process with a 64-bit strace and vice versa will not
  * work.  I don't know how to fix this.
  */
-asmlinkage int sys32_ptrace(int request, int pid, int addr, int data)
+long compat_arch_ptrace(struct task_struct *child, compat_long_t request,
+			compat_ulong_t caddr, compat_ulong_t cdata)
 {
-	struct task_struct *child;
+	int addr = caddr;
+	int data = cdata;
 	int ret;
 
-#if 0
-	printk("ptrace(r=%d,pid=%d,addr=%08lx,data=%08lx)\n",
-	       (int) request, (int) pid, (unsigned long) addr,
-	       (unsigned long) data);
-#endif
-	lock_kernel();
-	if (request == PTRACE_TRACEME) {
-		ret = ptrace_traceme();
-		goto out;
-	}
-
-	child = ptrace_get_task_struct(pid);
-	if (IS_ERR(child)) {
-		ret = PTR_ERR(child);
-		goto out;
-	}
-
-	if (request == PTRACE_ATTACH) {
-		ret = ptrace_attach(child);
-		goto out_tsk;
-	}
-
-	ret = ptrace_check_attach(child, request == PTRACE_KILL);
-	if (ret < 0)
-		goto out_tsk;
-
 	switch (request) {
 	/* when I and D space are separate, these will need to be fixed. */
 	case PTRACE_PEEKTEXT: /* read word at location addr. */
@@ -214,7 +185,7 @@ asmlinkage int sys32_ptrace(int request, int pid, int addr, int data)
 			if (!cpu_has_dsp) {
 				tmp = 0;
 				ret = -EIO;
-				goto out_tsk;
+				goto out;
 			}
 			dregs = __get_dsp_regs(child);
 			tmp = (unsigned long) (dregs[addr - DSP_BASE]);
@@ -224,14 +195,14 @@ asmlinkage int sys32_ptrace(int request, int pid, int addr, int data)
 			if (!cpu_has_dsp) {
 				tmp = 0;
 				ret = -EIO;
-				goto out_tsk;
+				goto out;
 			}
 			tmp = child->thread.dsp.dspcontrol;
 			break;
 		default:
 			tmp = 0;
 			ret = -EIO;
-			goto out_tsk;
+			goto out;
 		}
 		ret = put_user(tmp, (unsigned __user *) (unsigned long) data);
 		break;
@@ -410,14 +381,20 @@ asmlinkage int sys32_ptrace(int request, int pid, int addr, int data)
 				(unsigned long __user *) (unsigned long) data);
 		break;
 
+	case PTRACE_GET_WATCH_REGS:
+		ret = ptrace_get_watch_regs(child,
+			(struct pt_watch_regs __user *) (unsigned long) addr);
+		break;
+
+	case PTRACE_SET_WATCH_REGS:
+		ret = ptrace_set_watch_regs(child,
+			(struct pt_watch_regs __user *) (unsigned long) addr);
+		break;
+
 	default:
 		ret = ptrace_request(child, request, addr, data);
 		break;
 	}
-
-out_tsk:
-	put_task_struct(child);
 out:
-	unlock_kernel();
 	return ret;
 }
diff --git a/arch/mips/kernel/scall64-n32.S b/arch/mips/kernel/scall64-n32.S
index da7f1b6..324c549 100644
--- a/arch/mips/kernel/scall64-n32.S
+++ b/arch/mips/kernel/scall64-n32.S
@@ -219,7 +219,7 @@ EXPORT(sysn32_call_table)
 	PTR	compat_sys_getrusage
 	PTR	compat_sys_sysinfo
 	PTR	compat_sys_times
-	PTR	sys32_ptrace
+	PTR	compat_sys_ptrace
 	PTR	sys_getuid			/* 6100 */
 	PTR	sys_syslog
 	PTR	sys_getgid
diff --git a/arch/mips/kernel/scall64-o32.S b/arch/mips/kernel/scall64-o32.S
index d7cd1aa..85fedac 100644
--- a/arch/mips/kernel/scall64-o32.S
+++ b/arch/mips/kernel/scall64-o32.S
@@ -231,7 +231,7 @@ sys_call_table:
 	PTR	sys_setuid
 	PTR	sys_getuid
 	PTR	compat_sys_stime		/* 4025 */
-	PTR	sys32_ptrace
+	PTR	compat_sys_ptrace
 	PTR	sys_alarm
 	PTR	sys_ni_syscall			/* was sys_fstat */
 	PTR	sys_pause
diff --git a/arch/mips/kernel/signal32.c b/arch/mips/kernel/signal32.c
index 572c610..652709b 100644
--- a/arch/mips/kernel/signal32.c
+++ b/arch/mips/kernel/signal32.c
@@ -482,6 +482,18 @@ int copy_siginfo_to_user32(compat_siginfo_t __user *to, siginfo_t *from)
 	return err;
 }
 
+int copy_siginfo_from_user32(siginfo_t *to, compat_siginfo_t __user *from)
+{
+	memset(to, 0, sizeof *to);
+
+	if (copy_from_user(to, from, 3*sizeof(int)) ||
+	    copy_from_user(to->_sifields._pad,
+			   from->_sifields._pad, SI_PAD_SIZE32))
+		return -EFAULT;
+
+	return 0;
+}
+
 asmlinkage void sys32_sigreturn(nabi_no_regargs struct pt_regs regs)
 {
 	struct sigframe32 __user *frame;
diff --git a/arch/mips/kernel/smp.c b/arch/mips/kernel/smp.c
index 4410f17..7b59cfb 100644
--- a/arch/mips/kernel/smp.c
+++ b/arch/mips/kernel/smp.c
@@ -121,6 +121,8 @@ asmlinkage __cpuinit void start_secondary(void)
 	cpu = smp_processor_id();
 	cpu_data[cpu].udelay_val = loops_per_jiffy;
 
+	notify_cpu_starting(cpu);
+
 	mp_ops->smp_finish();
 	set_cpu_sibling_map(cpu);
 
diff --git a/arch/mips/kernel/syscall.c b/arch/mips/kernel/syscall.c
index 343015a..37970d9 100644
--- a/arch/mips/kernel/syscall.c
+++ b/arch/mips/kernel/syscall.c
@@ -7,7 +7,6 @@
  * Copyright (C) 1999, 2000 Silicon Graphics, Inc.
  * Copyright (C) 2001 MIPS Technologies, Inc.
  */
-#include <linux/a.out.h>
 #include <linux/capability.h>
 #include <linux/errno.h>
 #include <linux/linkage.h>
diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c
index b602ac6..80b9e07 100644
--- a/arch/mips/kernel/traps.c
+++ b/arch/mips/kernel/traps.c
@@ -42,6 +42,7 @@
 #include <asm/tlbdebug.h>
 #include <asm/traps.h>
 #include <asm/uaccess.h>
+#include <asm/watch.h>
 #include <asm/mmu_context.h>
 #include <asm/types.h>
 #include <asm/stacktrace.h>
@@ -912,13 +913,26 @@ asmlinkage void do_mdmx(struct pt_regs *regs)
 
 asmlinkage void do_watch(struct pt_regs *regs)
 {
+	u32 cause;
+
 	/*
-	 * We use the watch exception where available to detect stack
-	 * overflows.
+	 * Clear WP (bit 22) bit of cause register so we don't loop
+	 * forever.
 	 */
-	dump_tlb_all();
-	show_regs(regs);
-	panic("Caught WATCH exception - probably caused by stack overflow.");
+	cause = read_c0_cause();
+	cause &= ~(1 << 22);
+	write_c0_cause(cause);
+
+	/*
+	 * If the current thread has the watch registers loaded, save
+	 * their values and send SIGTRAP.  Otherwise another thread
+	 * left the registers set, clear them and continue.
+	 */
+	if (test_tsk_thread_flag(current, TIF_LOAD_WATCH)) {
+		mips_read_watch_registers();
+		force_sig(SIGTRAP, current);
+	} else
+		mips_clear_watch_registers();
 }
 
 asmlinkage void do_mcheck(struct pt_regs *regs)
diff --git a/arch/mips/kernel/watch.c b/arch/mips/kernel/watch.c
new file mode 100644
index 0000000..c154069
--- /dev/null
+++ b/arch/mips/kernel/watch.c
@@ -0,0 +1,188 @@
+/*
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Copyright (C) 2008 David Daney
+ */
+
+#include <linux/sched.h>
+
+#include <asm/processor.h>
+#include <asm/watch.h>
+
+/*
+ * Install the watch registers for the current thread.  A maximum of
+ * four registers are installed although the machine may have more.
+ */
+void mips_install_watch_registers(void)
+{
+	struct mips3264_watch_reg_state *watches =
+		&current->thread.watch.mips3264;
+	switch (current_cpu_data.watch_reg_use_cnt) {
+	default:
+		BUG();
+	case 4:
+		write_c0_watchlo3(watches->watchlo[3]);
+		/* Write 1 to the I, R, and W bits to clear them, and
+		   1 to G so all ASIDs are trapped. */
+		write_c0_watchhi3(0x40000007 | watches->watchhi[3]);
+	case 3:
+		write_c0_watchlo2(watches->watchlo[2]);
+		write_c0_watchhi2(0x40000007 | watches->watchhi[2]);
+	case 2:
+		write_c0_watchlo1(watches->watchlo[1]);
+		write_c0_watchhi1(0x40000007 | watches->watchhi[1]);
+	case 1:
+		write_c0_watchlo0(watches->watchlo[0]);
+		write_c0_watchhi0(0x40000007 | watches->watchhi[0]);
+	}
+}
+
+/*
+ * Read back the watchhi registers so the user space debugger has
+ * access to the I, R, and W bits.  A maximum of four registers are
+ * read although the machine may have more.
+ */
+void mips_read_watch_registers(void)
+{
+	struct mips3264_watch_reg_state *watches =
+		&current->thread.watch.mips3264;
+	switch (current_cpu_data.watch_reg_use_cnt) {
+	default:
+		BUG();
+	case 4:
+		watches->watchhi[3] = (read_c0_watchhi3() & 0x0fff);
+	case 3:
+		watches->watchhi[2] = (read_c0_watchhi2() & 0x0fff);
+	case 2:
+		watches->watchhi[1] = (read_c0_watchhi1() & 0x0fff);
+	case 1:
+		watches->watchhi[0] = (read_c0_watchhi0() & 0x0fff);
+	}
+	if (current_cpu_data.watch_reg_use_cnt == 1 &&
+	    (watches->watchhi[0] & 7) == 0) {
+		/* Pathological case of release 1 architecture that
+		 * doesn't set the condition bits.  We assume that
+		 * since we got here, the watch condition was met and
+		 * signal that the conditions requested in watchlo
+		 * were met.  */
+		watches->watchhi[0] |= (watches->watchlo[0] & 7);
+	}
+ }
+
+/*
+ * Disable all watch registers.  Although only four registers are
+ * installed, all are cleared to eliminate the possibility of endless
+ * looping in the watch handler.
+ */
+void mips_clear_watch_registers(void)
+{
+	switch (current_cpu_data.watch_reg_count) {
+	default:
+		BUG();
+	case 8:
+		write_c0_watchlo7(0);
+	case 7:
+		write_c0_watchlo6(0);
+	case 6:
+		write_c0_watchlo5(0);
+	case 5:
+		write_c0_watchlo4(0);
+	case 4:
+		write_c0_watchlo3(0);
+	case 3:
+		write_c0_watchlo2(0);
+	case 2:
+		write_c0_watchlo1(0);
+	case 1:
+		write_c0_watchlo0(0);
+	}
+}
+
+__cpuinit void mips_probe_watch_registers(struct cpuinfo_mips *c)
+{
+	unsigned int t;
+
+	if ((c->options & MIPS_CPU_WATCH) == 0)
+		return;
+	/*
+	 * Check which of the I,R and W bits are supported, then
+	 * disable the register.
+	 */
+	write_c0_watchlo0(7);
+	t = read_c0_watchlo0();
+	write_c0_watchlo0(0);
+	c->watch_reg_masks[0] = t & 7;
+
+	/* Write the mask bits and read them back to determine which
+	 * can be used. */
+	c->watch_reg_count = 1;
+	c->watch_reg_use_cnt = 1;
+	t = read_c0_watchhi0();
+	write_c0_watchhi0(t | 0xff8);
+	t = read_c0_watchhi0();
+	c->watch_reg_masks[0] |= (t & 0xff8);
+	if ((t & 0x80000000) == 0)
+		return;
+
+	write_c0_watchlo1(7);
+	t = read_c0_watchlo1();
+	write_c0_watchlo1(0);
+	c->watch_reg_masks[1] = t & 7;
+
+	c->watch_reg_count = 2;
+	c->watch_reg_use_cnt = 2;
+	t = read_c0_watchhi1();
+	write_c0_watchhi1(t | 0xff8);
+	t = read_c0_watchhi1();
+	c->watch_reg_masks[1] |= (t & 0xff8);
+	if ((t & 0x80000000) == 0)
+		return;
+
+	write_c0_watchlo2(7);
+	t = read_c0_watchlo2();
+	write_c0_watchlo2(0);
+	c->watch_reg_masks[2] = t & 7;
+
+	c->watch_reg_count = 3;
+	c->watch_reg_use_cnt = 3;
+	t = read_c0_watchhi2();
+	write_c0_watchhi2(t | 0xff8);
+	t = read_c0_watchhi2();
+	c->watch_reg_masks[2] |= (t & 0xff8);
+	if ((t & 0x80000000) == 0)
+		return;
+
+	write_c0_watchlo3(7);
+	t = read_c0_watchlo3();
+	write_c0_watchlo3(0);
+	c->watch_reg_masks[3] = t & 7;
+
+	c->watch_reg_count = 4;
+	c->watch_reg_use_cnt = 4;
+	t = read_c0_watchhi3();
+	write_c0_watchhi3(t | 0xff8);
+	t = read_c0_watchhi3();
+	c->watch_reg_masks[3] |= (t & 0xff8);
+	if ((t & 0x80000000) == 0)
+		return;
+
+	/* We use at most 4, but probe and report up to 8. */
+	c->watch_reg_count = 5;
+	t = read_c0_watchhi4();
+	if ((t & 0x80000000) == 0)
+		return;
+
+	c->watch_reg_count = 6;
+	t = read_c0_watchhi5();
+	if ((t & 0x80000000) == 0)
+		return;
+
+	c->watch_reg_count = 7;
+	t = read_c0_watchhi6();
+	if ((t & 0x80000000) == 0)
+		return;
+
+	c->watch_reg_count = 8;
+}