powerpc: Hardware breakpoints rewrite to handle non DABR breakpoint r…

…egisters

This is a rewrite so that we don't assume we are using the DABR throughout the
code.  We now use the arch_hw_breakpoint to store the breakpoint in a generic
manner in the thread_struct, rather than storing the raw DABR value.

The ptrace GET/SET_DEBUGREG interface currently passes the raw DABR in from
userspace.  We keep this functionality, so that future changes (like the POWER8
DAWR), will still fake the DABR to userspace.

Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/include/asm/debug.h

@@ -4,6 +4,8 @@
 #ifndef _ASM_POWERPC_DEBUG_H
 #define _ASM_POWERPC_DEBUG_H
 
+#include <asm/hw_breakpoint.h>
+
 struct pt_regs;
 
 extern struct dentry *powerpc_debugfs_root;
@@ -15,7 +17,7 @@ extern int (*__debugger_ipi)(struct pt_regs *regs);
 extern int (*__debugger_bpt)(struct pt_regs *regs);
 extern int (*__debugger_sstep)(struct pt_regs *regs);
 extern int (*__debugger_iabr_match)(struct pt_regs *regs);
-extern int (*__debugger_dabr_match)(struct pt_regs *regs);
+extern int (*__debugger_break_match)(struct pt_regs *regs);
 extern int (*__debugger_fault_handler)(struct pt_regs *regs);
 
 #define DEBUGGER_BOILERPLATE(__NAME) \
@@ -31,7 +33,7 @@ DEBUGGER_BOILERPLATE(debugger_ipi)
 DEBUGGER_BOILERPLATE(debugger_bpt)
 DEBUGGER_BOILERPLATE(debugger_sstep)
 DEBUGGER_BOILERPLATE(debugger_iabr_match)
-DEBUGGER_BOILERPLATE(debugger_dabr_match)
+DEBUGGER_BOILERPLATE(debugger_break_match)
 DEBUGGER_BOILERPLATE(debugger_fault_handler)
 
 #else
@@ -40,17 +42,18 @@ static inline int debugger_ipi(struct pt_regs *regs) { return 0; }
 static inline int debugger_bpt(struct pt_regs *regs) { return 0; }
 static inline int debugger_sstep(struct pt_regs *regs) { return 0; }
 static inline int debugger_iabr_match(struct pt_regs *regs) { return 0; }
-static inline int debugger_dabr_match(struct pt_regs *regs) { return 0; }
+static inline int debugger_break_match(struct pt_regs *regs) { return 0; }
 static inline int debugger_fault_handler(struct pt_regs *regs) { return 0; }
 #endif
 
-extern int set_dabr(unsigned long dabr, unsigned long dabrx);
+int set_break(struct arch_hw_breakpoint *brk);
 #ifdef CONFIG_PPC_ADV_DEBUG_REGS
 extern void do_send_trap(struct pt_regs *regs, unsigned long address,
 			 unsigned long error_code, int signal_code, int brkpt);
 #else
-extern void do_dabr(struct pt_regs *regs, unsigned long address,
-		    unsigned long error_code);
+
+extern void do_break(struct pt_regs *regs, unsigned long address,
+		     unsigned long error_code);
 #endif
 
 #endif /* _ASM_POWERPC_DEBUG_H */

arch/powerpc/include/asm/hw_breakpoint.h

@@ -24,16 +24,30 @@
 #define _PPC_BOOK3S_64_HW_BREAKPOINT_H
 
 #ifdef	__KERNEL__
-#ifdef CONFIG_HAVE_HW_BREAKPOINT
-
 struct arch_hw_breakpoint {
 	unsigned long	address;
-	unsigned long	dabrx;
-	int		type;
-	u8		len; /* length of the target data symbol */
-	bool		extraneous_interrupt;
+	u16		type;
+	u16		len; /* length of the target data symbol */
 };
 
+/* Note: Don't change the the first 6 bits below as they are in the same order
+ * as the dabr and dabrx.
+ */
+#define HW_BRK_TYPE_READ		0x01
+#define HW_BRK_TYPE_WRITE		0x02
+#define HW_BRK_TYPE_TRANSLATE		0x04
+#define HW_BRK_TYPE_USER		0x08
+#define HW_BRK_TYPE_KERNEL		0x10
+#define HW_BRK_TYPE_HYP			0x20
+#define HW_BRK_TYPE_EXTRANEOUS_IRQ	0x80
+
+/* bits that overlap with the bottom 3 bits of the dabr */
+#define HW_BRK_TYPE_RDWR	(HW_BRK_TYPE_READ | HW_BRK_TYPE_WRITE)
+#define HW_BRK_TYPE_DABR	(HW_BRK_TYPE_RDWR | HW_BRK_TYPE_TRANSLATE)
+#define HW_BRK_TYPE_PRIV_ALL	(HW_BRK_TYPE_USER | HW_BRK_TYPE_KERNEL | \
+				 HW_BRK_TYPE_HYP)
+
+#ifdef CONFIG_HAVE_HW_BREAKPOINT
 #include <linux/kdebug.h>
 #include <asm/reg.h>
 #include <asm/debug.h>
@@ -62,7 +76,12 @@ extern void ptrace_triggered(struct perf_event *bp,
 			struct perf_sample_data *data, struct pt_regs *regs);
 static inline void hw_breakpoint_disable(void)
 {
-	set_dabr(0, 0);
+	struct arch_hw_breakpoint brk;
+
+	brk.address = 0;
+	brk.type = 0;
+	brk.len = 0;
+	set_break(&brk);
 }
 extern void thread_change_pc(struct task_struct *tsk, struct pt_regs *regs);
 

arch/powerpc/include/asm/processor.h

@@ -33,6 +33,7 @@
 #include <linux/cache.h>
 #include <asm/ptrace.h>
 #include <asm/types.h>
+#include <asm/hw_breakpoint.h>
 
 /* We do _not_ want to define new machine types at all, those must die
  * in favor of using the device-tree
@@ -225,8 +226,7 @@ struct thread_struct {
 	struct perf_event *last_hit_ubp;
 #endif /* CONFIG_HAVE_HW_BREAKPOINT */
 #endif
-	unsigned long	dabr;		/* Data address breakpoint register */
-	unsigned long	dabrx;		/*      ... extension  */
+	struct arch_hw_breakpoint hw_brk; /* info on the hardware breakpoint */
 	unsigned long	trap_nr;	/* last trap # on this thread */
 #ifdef CONFIG_ALTIVEC
 	/* Complete AltiVec register set */

arch/powerpc/include/asm/reg.h

@@ -206,9 +206,6 @@
 #define   DAWRX_KERNEL	(1UL << 1)
 #define   DAWRX_HYP	(1UL << 2)
 #define SPRN_DABR	0x3F5	/* Data Address Breakpoint Register */
-#define   DABR_TRANSLATION	(1UL << 2)
-#define   DABR_DATA_WRITE	(1UL << 1)
-#define   DABR_DATA_READ	(1UL << 0)
 #define SPRN_DABR2	0x13D	/* e300 */
 #define SPRN_DABRX	0x3F7	/* Data Address Breakpoint Register Extension */
 #define   DABRX_USER	(1UL << 0)

arch/powerpc/kernel/exceptions-64s.S

@@ -1251,7 +1251,7 @@ handle_dabr_fault:
 	ld      r4,_DAR(r1)
 	ld      r5,_DSISR(r1)
 	addi    r3,r1,STACK_FRAME_OVERHEAD
-	bl      .do_dabr
+	bl      .do_break
 12:	b       .ret_from_except_lite
 
 

arch/powerpc/kernel/hw_breakpoint.c

@@ -73,7 +73,7 @@ int arch_install_hw_breakpoint(struct perf_event *bp)
 	 * If so, DABR will be populated in single_step_dabr_instruction().
 	 */
 	if (current->thread.last_hit_ubp != bp)
-		set_dabr(info->address | info->type | DABR_TRANSLATION, info->dabrx);
+		set_break(info);
 
 	return 0;
 }
@@ -97,7 +97,7 @@ void arch_uninstall_hw_breakpoint(struct perf_event *bp)
 	}
 
 	*slot = NULL;
-	set_dabr(0, 0);
+	hw_breakpoint_disable();
 }
 
 /*
@@ -127,19 +127,13 @@ int arch_check_bp_in_kernelspace(struct perf_event *bp)
 
 int arch_bp_generic_fields(int type, int *gen_bp_type)
 {
-	switch (type) {
-	case DABR_DATA_READ:
-		*gen_bp_type = HW_BREAKPOINT_R;
-		break;
-	case DABR_DATA_WRITE:
-		*gen_bp_type = HW_BREAKPOINT_W;
-		break;
-	case (DABR_DATA_WRITE | DABR_DATA_READ):
-		*gen_bp_type = (HW_BREAKPOINT_W | HW_BREAKPOINT_R);
-		break;
-	default:
+	*gen_bp_type = 0;
+	if (type & HW_BRK_TYPE_READ)
+		*gen_bp_type |= HW_BREAKPOINT_R;
+	if (type & HW_BRK_TYPE_WRITE)
+		*gen_bp_type |= HW_BREAKPOINT_W;
+	if (*gen_bp_type == 0)
 		return -EINVAL;
-	}
 	return 0;
 }
 
@@ -154,29 +148,22 @@ int arch_validate_hwbkpt_settings(struct perf_event *bp)
 	if (!bp)
 		return ret;
 
-	switch (bp->attr.bp_type) {
-	case HW_BREAKPOINT_R:
-		info->type = DABR_DATA_READ;
-		break;
-	case HW_BREAKPOINT_W:
-		info->type = DABR_DATA_WRITE;
-		break;
-	case HW_BREAKPOINT_R | HW_BREAKPOINT_W:
-		info->type = (DABR_DATA_READ | DABR_DATA_WRITE);
-		break;
-	default:
+	info->type = HW_BRK_TYPE_TRANSLATE;
+	if (bp->attr.bp_type & HW_BREAKPOINT_R)
+		info->type |= HW_BRK_TYPE_READ;
+	if (bp->attr.bp_type & HW_BREAKPOINT_W)
+		info->type |= HW_BRK_TYPE_WRITE;
+	if (info->type == HW_BRK_TYPE_TRANSLATE)
+		/* must set alteast read or write */
 		return ret;
-	}
-
+	if (!(bp->attr.exclude_user))
+		info->type |= HW_BRK_TYPE_USER;
+	if (!(bp->attr.exclude_kernel))
+		info->type |= HW_BRK_TYPE_KERNEL;
+	if (!(bp->attr.exclude_hv))
+		info->type |= HW_BRK_TYPE_HYP;
 	info->address = bp->attr.bp_addr;
 	info->len = bp->attr.bp_len;
-	info->dabrx = DABRX_ALL;
-	if (bp->attr.exclude_user)
-		info->dabrx &= ~DABRX_USER;
-	if (bp->attr.exclude_kernel)
-		info->dabrx &= ~DABRX_KERNEL;
-	if (bp->attr.exclude_hv)
-		info->dabrx &= ~DABRX_HYP;
 
 	/*
 	 * Since breakpoint length can be a maximum of HW_BREAKPOINT_LEN(8)
@@ -204,7 +191,7 @@ void thread_change_pc(struct task_struct *tsk, struct pt_regs *regs)
 
 	info = counter_arch_bp(tsk->thread.last_hit_ubp);
 	regs->msr &= ~MSR_SE;
-	set_dabr(info->address | info->type | DABR_TRANSLATION, info->dabrx);
+	set_break(info);
 	tsk->thread.last_hit_ubp = NULL;
 }
 
@@ -222,7 +209,7 @@ int __kprobes hw_breakpoint_handler(struct die_args *args)
 	unsigned long dar = regs->dar;
 
 	/* Disable breakpoints during exception handling */
-	set_dabr(0, 0);
+	hw_breakpoint_disable();
 
 	/*
 	 * The counter may be concurrently released but that can only
@@ -255,8 +242,9 @@ int __kprobes hw_breakpoint_handler(struct die_args *args)
 	 * we still need to single-step the instruction, but we don't
 	 * generate an event.
 	 */
-	info->extraneous_interrupt = !((bp->attr.bp_addr <= dar) &&
-			(dar - bp->attr.bp_addr < bp->attr.bp_len));
+	if (!((bp->attr.bp_addr <= dar) &&
+	      (dar - bp->attr.bp_addr < bp->attr.bp_len)))
+		info->type |= HW_BRK_TYPE_EXTRANEOUS_IRQ;
 
 	/* Do not emulate user-space instructions, instead single-step them */
 	if (user_mode(regs)) {
@@ -285,10 +273,10 @@ int __kprobes hw_breakpoint_handler(struct die_args *args)
 	 * As a policy, the callback is invoked in a 'trigger-after-execute'
 	 * fashion
 	 */
-	if (!info->extraneous_interrupt)
+	if (!(info->type & HW_BRK_TYPE_EXTRANEOUS_IRQ))
 		perf_bp_event(bp, regs);
 
-	set_dabr(info->address | info->type | DABR_TRANSLATION, info->dabrx);
+	set_break(info);
 out:
 	rcu_read_unlock();
 	return rc;
@@ -317,10 +305,10 @@ int __kprobes single_step_dabr_instruction(struct die_args *args)
 	 * We shall invoke the user-defined callback function in the single
 	 * stepping handler to confirm to 'trigger-after-execute' semantics
 	 */
-	if (!info->extraneous_interrupt)
+	if (!(info->type & HW_BRK_TYPE_EXTRANEOUS_IRQ))
 		perf_bp_event(bp, regs);
 
-	set_dabr(info->address | info->type | DABR_TRANSLATION, info->dabrx);
+	set_break(info);
 	current->thread.last_hit_ubp = NULL;
 
 	/*

arch/powerpc/kernel/kgdb.c

@@ -198,7 +198,7 @@ static int kgdb_iabr_match(struct pt_regs *regs)
 	return 1;
 }
 
-static int kgdb_dabr_match(struct pt_regs *regs)
+static int kgdb_break_match(struct pt_regs *regs)
 {
 	if (user_mode(regs))
 		return 0;
@@ -458,7 +458,7 @@ static void *old__debugger;
 static void *old__debugger_bpt;
 static void *old__debugger_sstep;
 static void *old__debugger_iabr_match;
-static void *old__debugger_dabr_match;
+static void *old__debugger_break_match;
 static void *old__debugger_fault_handler;
 
 int kgdb_arch_init(void)
@@ -468,15 +468,15 @@ int kgdb_arch_init(void)
 	old__debugger_bpt = __debugger_bpt;
 	old__debugger_sstep = __debugger_sstep;
 	old__debugger_iabr_match = __debugger_iabr_match;
-	old__debugger_dabr_match = __debugger_dabr_match;
+	old__debugger_break_match = __debugger_break_match;
 	old__debugger_fault_handler = __debugger_fault_handler;
 
 	__debugger_ipi = kgdb_call_nmi_hook;
 	__debugger = kgdb_debugger;
 	__debugger_bpt = kgdb_handle_breakpoint;
 	__debugger_sstep = kgdb_singlestep;
 	__debugger_iabr_match = kgdb_iabr_match;
-	__debugger_dabr_match = kgdb_dabr_match;
+	__debugger_break_match = kgdb_break_match;
 	__debugger_fault_handler = kgdb_not_implemented;
 
 	return 0;
@@ -489,6 +489,6 @@ void kgdb_arch_exit(void)
 	__debugger_bpt = old__debugger_bpt;
 	__debugger_sstep = old__debugger_sstep;
 	__debugger_iabr_match = old__debugger_iabr_match;
-	__debugger_dabr_match = old__debugger_dabr_match;
+	__debugger_breakx_match = old__debugger_break_match;
 	__debugger_fault_handler = old__debugger_fault_handler;
 }