MIPS: Add HARDWARE_WATCHPOINTS definitions and support code.

This is the main support code for the patch.  Here we just add the
code, the following patches hook it up.

Signed-off-by: David Daney <ddaney@avtrex.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

 create mode 100644 arch/mips/include/asm/watch.h
 create mode 100644 arch/mips/kernel/watch.c

6 files changed, 249 insertions, 1 deletions

diff --git a/arch/mips/include/asm/cpu-info.h b/arch/mips/include/asm/cpu-info.h
index 2de73dbb2e9e..744cd8fb107f 100644
--- a/arch/mips/include/asm/cpu-info.h
+++ b/arch/mips/include/asm/cpu-info.h
@@ -12,6 +12,8 @@
 #ifndef __ASM_CPU_INFO_H
 #define __ASM_CPU_INFO_H
 
+#include <linux/types.h>
+
 #include <asm/cache.h>
 
 /*
@@ -69,6 +71,10 @@ struct cpuinfo_mips {
         int                     tc_id;   /* Thread Context number */
 #endif
         void                    *data;  /* Additional data */
+        unsigned int            watch_reg_count;   /* Number that exist */
+        unsigned int            watch_reg_use_cnt; /* Usable by ptrace */
+#define NUM_WATCH_REGS 4
+        u16                     watch_reg_masks[NUM_WATCH_REGS];
 } __attribute__((aligned(SMP_CACHE_BYTES)));
 
 extern struct cpuinfo_mips cpu_data[];
diff --git a/arch/mips/include/asm/processor.h b/arch/mips/include/asm/processor.h
index a1e4453469f9..18ee58e39445 100644
--- a/arch/mips/include/asm/processor.h
+++ b/arch/mips/include/asm/processor.h
@@ -105,6 +105,19 @@ struct mips_dsp_state {
         {0,} \
 }
 
+struct mips3264_watch_reg_state {
+        /* The width of watchlo is 32 in a 32 bit kernel and 64 in a
+           64 bit kernel.  We use unsigned long as it has the same
+           property. */
+        unsigned long watchlo[NUM_WATCH_REGS];
+        /* Only the mask and IRW bits from watchhi. */
+        u16 watchhi[NUM_WATCH_REGS];
+};
+
+union mips_watch_reg_state {
+        struct mips3264_watch_reg_state mips3264;
+};
+
 typedef struct {
         unsigned long seg;
 } mm_segment_t;
@@ -137,6 +150,9 @@ struct thread_struct {
         /* Saved state of the DSP ASE, if available. */
         struct mips_dsp_state dsp;
 
+        /* Saved watch register state, if available. */
+        union mips_watch_reg_state watch;
+
         /* Other stuff associated with the thread. */
         unsigned long cp0_badvaddr;     /* Last user fault */
         unsigned long cp0_baduaddr;     /* Last kernel fault accessing USEG */
@@ -193,6 +209,10 @@ struct thread_struct {
                 .dspcontrol     = 0,                            \
         },                                                      \
         /*                                                      \
+         * saved watch register stuff                           \
+         */                                                     \
+        .watch = {{{0,},},},                                    \
+        /*                                                      \
          * Other stuff associated with the process              \
          */                                                     \
         .cp0_badvaddr           = 0,                            \
diff --git a/arch/mips/include/asm/thread_info.h b/arch/mips/include/asm/thread_info.h
index bb3060699df2..3f76de73c943 100644
--- a/arch/mips/include/asm/thread_info.h
+++ b/arch/mips/include/asm/thread_info.h
@@ -124,6 +124,7 @@ register struct thread_info *__current_thread_info __asm__("$28");
 #define TIF_32BIT_REGS          22      /* also implies 16/32 fprs */
 #define TIF_32BIT_ADDR          23      /* 32-bit address space (o32/n32) */
 #define TIF_FPUBOUND            24      /* thread bound to FPU-full CPU set */
+#define TIF_LOAD_WATCH          25      /* If set, load watch registers */
 #define TIF_SYSCALL_TRACE       31      /* syscall trace active */
 
 #define _TIF_SYSCALL_TRACE      (1<<TIF_SYSCALL_TRACE)
@@ -140,6 +141,7 @@ register struct thread_info *__current_thread_info __asm__("$28");
 #define _TIF_32BIT_REGS         (1<<TIF_32BIT_REGS)
 #define _TIF_32BIT_ADDR         (1<<TIF_32BIT_ADDR)
 #define _TIF_FPUBOUND           (1<<TIF_FPUBOUND)
+#define _TIF_LOAD_WATCH         (1<<TIF_LOAD_WATCH)
 
 /* work to do on interrupt/exception return */
 #define _TIF_WORK_MASK          (0x0000ffef & ~_TIF_SECCOMP)
diff --git a/arch/mips/include/asm/watch.h b/arch/mips/include/asm/watch.h
new file mode 100644
index 000000000000..20126ec79359
--- /dev/null
+++ b/arch/mips/include/asm/watch.h
@@ -0,0 +1,32 @@
+/*
+ * 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
+ */
+#ifndef _ASM_WATCH_H
+#define _ASM_WATCH_H
+
+#include <linux/bitops.h>
+
+#include <asm/mipsregs.h>
+
+void mips_install_watch_registers(void);
+void mips_read_watch_registers(void);
+void mips_clear_watch_registers(void);
+void mips_probe_watch_registers(struct cpuinfo_mips *c);
+
+#ifdef CONFIG_HARDWARE_WATCHPOINTS
+#define __restore_watch() do {                                          \
+        if (unlikely(test_bit(TIF_LOAD_WATCH,                           \
+                              &current_thread_info()->flags))) {        \
+                mips_install_watch_registers();                         \
+        }                                                               \
+} while (0)
+
+#else
+#define __restore_watch() do {} while (0)
+#endif
+
+#endif /* _ASM_WATCH_H */
diff --git a/arch/mips/kernel/Makefile b/arch/mips/kernel/Makefile
index 25775cb54000..d9da7112aaf8 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/watch.c b/arch/mips/kernel/watch.c
new file mode 100644
index 000000000000..c15406968030
--- /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;
+}