hw-breakpoints: prepare the code for Hardware Breakpoint interfaces

The generic hardware breakpoint interface provides an abstraction of
hardware breakpoints in front of specific arch implementations for both kernel
and user side breakpoints.
This includes execution breakpoints and read/write breakpoints, also known as
"watchpoints".

This patch introduces header files containing constants, structure definitions
and declaration of functions used by the hardware breakpoint core and x86
specific code.
It also introduces an array based storage for the debug-register values in
'struct thread_struct', while modifying all users of debugreg<n> member in the
structure.

[ Impact: add headers for new hardware breakpoint interface ]

Original-patch-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: K.Prasad <prasad@linux.vnet.ibm.com>
Reviewed-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

4 files changed, 92 insertions, 8 deletions

diff --git a/arch/x86/include/asm/a.out-core.h b/arch/x86/include/asm/a.out-core.h
index bb70e397aa84..fc4685dd6e4d 100644
--- a/arch/x86/include/asm/a.out-core.h
+++ b/arch/x86/include/asm/a.out-core.h
@@ -32,10 +32,10 @@ static inline void aout_dump_thread(struct pt_regs *regs, struct user *dump)
                         >> PAGE_SHIFT;
         dump->u_dsize -= dump->u_tsize;
         dump->u_ssize = 0;
-        dump->u_debugreg[0] = current->thread.debugreg0;
-        dump->u_debugreg[1] = current->thread.debugreg1;
-        dump->u_debugreg[2] = current->thread.debugreg2;
-        dump->u_debugreg[3] = current->thread.debugreg3;
+        dump->u_debugreg[0] = current->thread.debugreg[0];
+        dump->u_debugreg[1] = current->thread.debugreg[1];
+        dump->u_debugreg[2] = current->thread.debugreg[2];
+        dump->u_debugreg[3] = current->thread.debugreg[3];
         dump->u_debugreg[4] = 0;
         dump->u_debugreg[5] = 0;
         dump->u_debugreg[6] = current->thread.debugreg6;
diff --git a/arch/x86/include/asm/debugreg.h b/arch/x86/include/asm/debugreg.h
index 3ea6f37be9e2..23439fbb1d0e 100644
--- a/arch/x86/include/asm/debugreg.h
+++ b/arch/x86/include/asm/debugreg.h
@@ -18,6 +18,7 @@
 #define DR_TRAP1        (0x2)           /* db1 */
 #define DR_TRAP2        (0x4)           /* db2 */
 #define DR_TRAP3        (0x8)           /* db3 */
+#define DR_TRAP_BITS    (DR_TRAP0|DR_TRAP1|DR_TRAP2|DR_TRAP3)
 
 #define DR_STEP         (0x4000)        /* single-step */
 #define DR_SWITCH       (0x8000)        /* task switch */
@@ -49,6 +50,8 @@
 
 #define DR_LOCAL_ENABLE_SHIFT 0    /* Extra shift to the local enable bit */
 #define DR_GLOBAL_ENABLE_SHIFT 1   /* Extra shift to the global enable bit */
+#define DR_LOCAL_ENABLE (0x1)      /* Local enable for reg 0 */
+#define DR_GLOBAL_ENABLE (0x2)     /* Global enable for reg 0 */
 #define DR_ENABLE_SIZE 2           /* 2 enable bits per register */
 
 #define DR_LOCAL_ENABLE_MASK (0x55)  /* Set  local bits for all 4 regs */
@@ -67,4 +70,30 @@
 #define DR_LOCAL_SLOWDOWN (0x100)   /* Local slow the pipeline */
 #define DR_GLOBAL_SLOWDOWN (0x200)  /* Global slow the pipeline */
 
+/*
+ * HW breakpoint additions
+ */
+#ifdef __KERNEL__
+
+/* For process management */
+extern void flush_thread_hw_breakpoint(struct task_struct *tsk);
+extern int copy_thread_hw_breakpoint(struct task_struct *tsk,
+                struct task_struct *child, unsigned long clone_flags);
+
+/* For CPU management */
+extern void load_debug_registers(void);
+static inline void hw_breakpoint_disable(void)
+{
+        /* Zero the control register for HW Breakpoint */
+        set_debugreg(0UL, 7);
+
+        /* Zero-out the individual HW breakpoint address registers */
+        set_debugreg(0UL, 0);
+        set_debugreg(0UL, 1);
+        set_debugreg(0UL, 2);
+        set_debugreg(0UL, 3);
+}
+
+#endif  /* __KERNEL__ */
+
 #endif /* _ASM_X86_DEBUGREG_H */
diff --git a/arch/x86/include/asm/hw_breakpoint.h b/arch/x86/include/asm/hw_breakpoint.h
new file mode 100644
index 000000000000..1acb4d45de70
--- /dev/null
+++ b/arch/x86/include/asm/hw_breakpoint.h
@@ -0,0 +1,55 @@
+#ifndef _I386_HW_BREAKPOINT_H
+#define _I386_HW_BREAKPOINT_H
+
+#ifdef  __KERNEL__
+#define __ARCH_HW_BREAKPOINT_H
+
+struct arch_hw_breakpoint {
+        char            *name; /* Contains name of the symbol to set bkpt */
+        unsigned long   address;
+        u8              len;
+        u8              type;
+};
+
+#include <linux/kdebug.h>
+#include <asm-generic/hw_breakpoint.h>
+
+/* Available HW breakpoint length encodings */
+#define HW_BREAKPOINT_LEN_1             0x40
+#define HW_BREAKPOINT_LEN_2             0x44
+#define HW_BREAKPOINT_LEN_4             0x4c
+#define HW_BREAKPOINT_LEN_EXECUTE       0x40
+
+#ifdef CONFIG_X86_64
+#define HW_BREAKPOINT_LEN_8             0x48
+#endif
+
+/* Available HW breakpoint type encodings */
+
+/* trigger on instruction execute */
+#define HW_BREAKPOINT_EXECUTE   0x80
+/* trigger on memory write */
+#define HW_BREAKPOINT_WRITE     0x81
+/* trigger on memory read or write */
+#define HW_BREAKPOINT_RW        0x83
+
+/* Total number of available HW breakpoint registers */
+#define HBP_NUM 4
+
+extern struct hw_breakpoint *hbp_kernel[HBP_NUM];
+DECLARE_PER_CPU(struct hw_breakpoint*, this_hbp_kernel[HBP_NUM]);
+extern unsigned int hbp_user_refcount[HBP_NUM];
+
+extern void arch_install_thread_hw_breakpoint(struct task_struct *tsk);
+extern void arch_uninstall_thread_hw_breakpoint(void);
+extern int arch_check_va_in_userspace(unsigned long va, u8 hbp_len);
+extern int arch_validate_hwbkpt_settings(struct hw_breakpoint *bp,
+                                                struct task_struct *tsk);
+extern void arch_update_user_hw_breakpoint(int pos, struct task_struct *tsk);
+extern void arch_flush_thread_hw_breakpoint(struct task_struct *tsk);
+extern void arch_update_kernel_hw_breakpoint(void *);
+extern int hw_breakpoint_exceptions_notify(struct notifier_block *unused,
+                                     unsigned long val, void *data);
+#endif  /* __KERNEL__ */
+#endif  /* _I386_HW_BREAKPOINT_H */
+
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 0b2fab0051e0..448b34a8e393 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -29,6 +29,7 @@ struct mm_struct;
 #include <linux/threads.h>
 #include <linux/init.h>
 
+#define HBP_NUM 4
 /*
  * Default implementation of macro that returns current
  * instruction pointer ("program counter").
@@ -431,12 +432,11 @@ struct thread_struct {
         unsigned long           fs;
         unsigned long           gs;
         /* Hardware debugging registers: */
-        unsigned long           debugreg0;
-        unsigned long           debugreg1;
-        unsigned long           debugreg2;
-        unsigned long           debugreg3;
+        unsigned long           debugreg[HBP_NUM];
         unsigned long           debugreg6;
         unsigned long           debugreg7;
+        /* Hardware breakpoint info */
+        struct hw_breakpoint    *hbp[HBP_NUM];
         /* Fault info: */
         unsigned long           cr2;
         unsigned long           trap_no;