MIPS: Ptrace support for HARDWARE_WATCHPOINTS

This is the final part of the watch register patch.  Here we hook up
ptrace so that the user space debugger (gdb), can set and read the
registers.

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

3 files changed, 155 insertions, 1 deletions

diff --git a/arch/mips/include/asm/ptrace.h b/arch/mips/include/asm/ptrace.h
index c00cca24dae0..cd5e8a47812b 100644
--- a/arch/mips/include/asm/ptrace.h
+++ b/arch/mips/include/asm/ptrace.h
@@ -74,11 +74,57 @@ struct pt_regs {
 #define PTRACE_POKEDATA_3264    0xc3
 #define PTRACE_GET_THREAD_AREA_3264     0xc4
 
+/* Read and write watchpoint registers.  */
+enum pt_watch_style {
+        pt_watch_style_mips32,
+        pt_watch_style_mips64
+};
+struct mips32_watch_regs {
+        uint32_t watchlo[8];
+        /* Lower 16 bits of watchhi. */
+        uint16_t watchhi[8];
+        /* Valid mask and I R W bits.
+         * bit 0 -- 1 if W bit is usable.
+         * bit 1 -- 1 if R bit is usable.
+         * bit 2 -- 1 if I bit is usable.
+         * bits 3 - 11 -- Valid watchhi mask bits.
+         */
+        uint16_t watch_masks[8];
+        /* The number of valid watch register pairs.  */
+        uint32_t num_valid;
+} __attribute__((aligned(8)));
+
+struct mips64_watch_regs {
+        uint64_t watchlo[8];
+        uint16_t watchhi[8];
+        uint16_t watch_masks[8];
+        uint32_t num_valid;
+} __attribute__((aligned(8)));
+
+struct pt_watch_regs {
+        enum pt_watch_style style;
+        union {
+                struct mips32_watch_regs mips32;
+                struct mips32_watch_regs mips64;
+        };
+};
+
+#define PTRACE_GET_WATCH_REGS   0xd0
+#define PTRACE_SET_WATCH_REGS   0xd1
+
 #ifdef __KERNEL__
 
+#include <linux/compiler.h>
 #include <linux/linkage.h>
 #include <asm/isadep.h>
 
+struct task_struct;
+
+extern int ptrace_get_watch_regs(struct task_struct *child,
+        struct pt_watch_regs __user *addr);
+extern int ptrace_set_watch_regs(struct task_struct *child,
+        struct pt_watch_regs __user *addr);
+
 /*
  * Does the process account for user or for system time?
  */
diff --git a/arch/mips/kernel/ptrace.c b/arch/mips/kernel/ptrace.c
index 96ffc9c6d194..054861ccb4dd 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 cac56a8c8679..e45105e3ef00 100644
--- a/arch/mips/kernel/ptrace32.c
+++ b/arch/mips/kernel/ptrace32.c
@@ -387,6 +387,16 @@ long compat_arch_ptrace(struct task_struct *child, compat_long_t request,
                                 (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;