2 files changed, 307 insertions, 91 deletions

diff --git a/arch/powerpc/kernel/hw_breakpoint.c b/arch/powerpc/kernel/hw_breakpoint.c
index 4366bd0c90c4..5fdc6c4f14af 100644
--- a/arch/powerpc/kernel/hw_breakpoint.c
+++ b/arch/powerpc/kernel/hw_breakpoint.c
@@ -31,7 +31,7 @@
  * Stores the breakpoints currently in use on each breakpoint address
  * register for every cpu
  */
-static DEFINE_PER_CPU(struct perf_event *, bp_per_reg);
+static DEFINE_PER_CPU(struct perf_event *, bp_per_reg[HBP_NUM_MAX]);
 
 /*
  * Returns total number of data or instruction breakpoints available.
@@ -43,6 +43,17 @@ int hw_breakpoint_slots(int type)
 	return 0;		/* no instruction breakpoints available */
 }
 
+static bool single_step_pending(void)
+{
+	int i;
+
+	for (i = 0; i < nr_wp_slots(); i++) {
+		if (current->thread.last_hit_ubp[i])
+			return true;
+	}
+	return false;
+}
+
 /*
  * Install a perf counter breakpoint.
  *
@@ -55,16 +66,26 @@ int hw_breakpoint_slots(int type)
 int arch_install_hw_breakpoint(struct perf_event *bp)
 {
 	struct arch_hw_breakpoint *info = counter_arch_bp(bp);
-	struct perf_event **slot = this_cpu_ptr(&bp_per_reg);
+	struct perf_event **slot;
+	int i;
+
+	for (i = 0; i < nr_wp_slots(); i++) {
+		slot = this_cpu_ptr(&bp_per_reg[i]);
+		if (!*slot) {
+			*slot = bp;
+			break;
+		}
+	}
 
-	*slot = bp;
+	if (WARN_ONCE(i == nr_wp_slots(), "Can't find any breakpoint slot"))
+		return -EBUSY;
 
 	/*
 	 * Do not install DABR values if the instruction must be single-stepped.
 	 * If so, DABR will be populated in single_step_dabr_instruction().
 	 */
-	if (current->thread.last_hit_ubp != bp)
-		__set_breakpoint(0, info);
+	if (!single_step_pending())
+		__set_breakpoint(i, info);
 
 	return 0;
 }
@@ -80,15 +101,22 @@ int arch_install_hw_breakpoint(struct perf_event *bp)
  */
 void arch_uninstall_hw_breakpoint(struct perf_event *bp)
 {
-	struct perf_event **slot = this_cpu_ptr(&bp_per_reg);
+	struct arch_hw_breakpoint null_brk = {0};
+	struct perf_event **slot;
+	int i;
 
-	if (*slot != bp) {
-		WARN_ONCE(1, "Can't find the breakpoint");
-		return;
+	for (i = 0; i < nr_wp_slots(); i++) {
+		slot = this_cpu_ptr(&bp_per_reg[i]);
+		if (*slot == bp) {
+			*slot = NULL;
+			break;
+		}
 	}
 
-	*slot = NULL;
-	hw_breakpoint_disable();
+	if (WARN_ONCE(i == nr_wp_slots(), "Can't find any breakpoint slot"))
+		return;
+
+	__set_breakpoint(i, &null_brk);
 }
 
 static bool is_ptrace_bp(struct perf_event *bp)
@@ -108,8 +136,14 @@ void arch_unregister_hw_breakpoint(struct perf_event *bp)
 	 * restoration variables to prevent dangling pointers.
 	 * FIXME, this should not be using bp->ctx at all! Sayeth peterz.
 	 */
-	if (bp->ctx && bp->ctx->task && bp->ctx->task != ((void *)-1L))
-		bp->ctx->task->thread.last_hit_ubp = NULL;
+	if (bp->ctx && bp->ctx->task && bp->ctx->task != ((void *)-1L)) {
+		int i;
+
+		for (i = 0; i < nr_wp_slots(); i++) {
+			if (bp->ctx->task->thread.last_hit_ubp[i] == bp)
+				bp->ctx->task->thread.last_hit_ubp[i] = NULL;
+		}
+	}
 }
 
 /*
@@ -221,90 +255,209 @@ int hw_breakpoint_arch_parse(struct perf_event *bp,
 void thread_change_pc(struct task_struct *tsk, struct pt_regs *regs)
 {
 	struct arch_hw_breakpoint *info;
+	int i;
 
-	if (likely(!tsk->thread.last_hit_ubp))
-		return;
+	for (i = 0; i < nr_wp_slots(); i++) {
+		if (unlikely(tsk->thread.last_hit_ubp[i]))
+			goto reset;
+	}
+	return;
 
-	info = counter_arch_bp(tsk->thread.last_hit_ubp);
+reset:
 	regs->msr &= ~MSR_SE;
-	__set_breakpoint(0, info);
-	tsk->thread.last_hit_ubp = NULL;
+	for (i = 0; i < nr_wp_slots(); i++) {
+		info = counter_arch_bp(__this_cpu_read(bp_per_reg[i]));
+		__set_breakpoint(i, info);
+		tsk->thread.last_hit_ubp[i] = NULL;
+	}
 }
 
-static bool dar_within_range(unsigned long dar, struct arch_hw_breakpoint *info)
+static bool dar_in_user_range(unsigned long dar, struct arch_hw_breakpoint *info)
 {
 	return ((info->address <= dar) && (dar - info->address < info->len));
 }
 
-static bool
-dar_range_overlaps(unsigned long dar, int size, struct arch_hw_breakpoint *info)
+static bool dar_user_range_overlaps(unsigned long dar, int size,
+				    struct arch_hw_breakpoint *info)
+{
+	return ((dar < info->address + info->len) &&
+		(dar + size > info->address));
+}
+
+static bool dar_in_hw_range(unsigned long dar, struct arch_hw_breakpoint *info)
+{
+	unsigned long hw_start_addr, hw_end_addr;
+
+	hw_start_addr = ALIGN_DOWN(info->address, HW_BREAKPOINT_SIZE);
+	hw_end_addr = ALIGN(info->address + info->len, HW_BREAKPOINT_SIZE);
+
+	return ((hw_start_addr <= dar) && (hw_end_addr > dar));
+}
+
+static bool dar_hw_range_overlaps(unsigned long dar, int size,
+				  struct arch_hw_breakpoint *info)
 {
-	return ((dar <= info->address + info->len - 1) &&
-		(dar + size - 1 >= info->address));
+	unsigned long hw_start_addr, hw_end_addr;
+
+	hw_start_addr = ALIGN_DOWN(info->address, HW_BREAKPOINT_SIZE);
+	hw_end_addr = ALIGN(info->address + info->len, HW_BREAKPOINT_SIZE);
+
+	return ((dar < hw_end_addr) && (dar + size > hw_start_addr));
 }
 
 /*
- * Handle debug exception notifications.
+ * If hw has multiple DAWR registers, we also need to check all
+ * dawrx constraint bits to confirm this is _really_ a valid event.
  */
-static bool stepping_handler(struct pt_regs *regs, struct perf_event *bp,
-			     struct arch_hw_breakpoint *info)
+static bool check_dawrx_constraints(struct pt_regs *regs, int type,
+				    struct arch_hw_breakpoint *info)
 {
-	struct ppc_inst instr = ppc_inst(0);
-	int ret, type, size;
-	struct instruction_op op;
-	unsigned long addr = info->address;
+	if (OP_IS_LOAD(type) && !(info->type & HW_BRK_TYPE_READ))
+		return false;
 
-	if (__get_user_instr_inatomic(instr, (void __user *)regs->nip))
-		goto fail;
+	if (OP_IS_STORE(type) && !(info->type & HW_BRK_TYPE_WRITE))
+		return false;
 
-	ret = analyse_instr(&op, regs, instr);
-	type = GETTYPE(op.type);
-	size = GETSIZE(op.type);
+	if (is_kernel_addr(regs->nip) && !(info->type & HW_BRK_TYPE_KERNEL))
+		return false;
 
-	if (!ret && (type == LARX || type == STCX)) {
-		printk_ratelimited("Breakpoint hit on instruction that can't be emulated."
-				   " Breakpoint at 0x%lx will be disabled.\n", addr);
-		goto disable;
-	}
+	if (user_mode(regs) && !(info->type & HW_BRK_TYPE_USER))
+		return false;
+
+	return true;
+}
+
+/*
+ * Return true if the event is valid wrt dawr configuration,
+ * including extraneous exception. Otherwise return false.
+ */
+static bool check_constraints(struct pt_regs *regs, struct ppc_inst instr,
+			      int type, int size, struct arch_hw_breakpoint *info)
+{
+	bool in_user_range = dar_in_user_range(regs->dar, info);
+	bool dawrx_constraints;
 
 	/*
-	 * If it's extraneous event, we still need to emulate/single-
-	 * step the instruction, but we don't generate an event.
+	 * 8xx supports only one breakpoint and thus we can
+	 * unconditionally return true.
 	 */
-	if (size && !dar_range_overlaps(regs->dar, size, info))
-		info->type |= HW_BRK_TYPE_EXTRANEOUS_IRQ;
+	if (IS_ENABLED(CONFIG_PPC_8xx)) {
+		if (!in_user_range)
+			info->type |= HW_BRK_TYPE_EXTRANEOUS_IRQ;
+		return true;
+	}
 
-	/* Do not emulate user-space instructions, instead single-step them */
-	if (user_mode(regs)) {
-		current->thread.last_hit_ubp = bp;
-		regs->msr |= MSR_SE;
+	if (unlikely(ppc_inst_equal(instr, ppc_inst(0)))) {
+		if (in_user_range)
+			return true;
+
+		if (dar_in_hw_range(regs->dar, info)) {
+			info->type |= HW_BRK_TYPE_EXTRANEOUS_IRQ;
+			return true;
+		}
 		return false;
 	}
 
-	if (!emulate_step(regs, instr))
-		goto fail;
+	dawrx_constraints = check_dawrx_constraints(regs, type, info);
 
-	return true;
+	if (dar_user_range_overlaps(regs->dar, size, info))
+		return dawrx_constraints;
+
+	if (dar_hw_range_overlaps(regs->dar, size, info)) {
+		if (dawrx_constraints) {
+			info->type |= HW_BRK_TYPE_EXTRANEOUS_IRQ;
+			return true;
+		}
+	}
+	return false;
+}
+
+static void get_instr_detail(struct pt_regs *regs, struct ppc_inst *instr,
+			     int *type, int *size, bool *larx_stcx)
+{
+	struct instruction_op op;
+
+	if (__get_user_instr_inatomic(*instr, (void __user *)regs->nip))
+		return;
+
+	analyse_instr(&op, regs, *instr);
 
-fail:
 	/*
-	 * We've failed in reliably handling the hw-breakpoint. Unregister
-	 * it and throw a warning message to let the user know about it.
+	 * Set size = 8 if analyse_instr() fails. If it's a userspace
+	 * watchpoint(valid or extraneous), we can notify user about it.
+	 * If it's a kernel watchpoint, instruction  emulation will fail
+	 * in stepping_handler() and watchpoint will be disabled.
 	 */
-	WARN(1, "Unable to handle hardware breakpoint. Breakpoint at "
-		"0x%lx will be disabled.", addr);
+	*type = GETTYPE(op.type);
+	*size = !(*type == UNKNOWN) ? GETSIZE(op.type) : 8;
+	*larx_stcx = (*type == LARX || *type == STCX);
+}
+
+/*
+ * We've failed in reliably handling the hw-breakpoint. Unregister
+ * it and throw a warning message to let the user know about it.
+ */
+static void handler_error(struct perf_event *bp, struct arch_hw_breakpoint *info)
+{
+	WARN(1, "Unable to handle hardware breakpoint. Breakpoint at 0x%lx will be disabled.",
+	     info->address);
+	perf_event_disable_inatomic(bp);
+}
 
-disable:
+static void larx_stcx_err(struct perf_event *bp, struct arch_hw_breakpoint *info)
+{
+	printk_ratelimited("Breakpoint hit on instruction that can't be emulated. Breakpoint at 0x%lx will be disabled.\n",
+			   info->address);
 	perf_event_disable_inatomic(bp);
-	return false;
+}
+
+static bool stepping_handler(struct pt_regs *regs, struct perf_event **bp,
+			     struct arch_hw_breakpoint **info, int *hit,
+			     struct ppc_inst instr)
+{
+	int i;
+	int stepped;
+
+	/* Do not emulate user-space instructions, instead single-step them */
+	if (user_mode(regs)) {
+		for (i = 0; i < nr_wp_slots(); i++) {
+			if (!hit[i])
+				continue;
+			current->thread.last_hit_ubp[i] = bp[i];
+			info[i] = NULL;
+		}
+		regs->msr |= MSR_SE;
+		return false;
+	}
+
+	stepped = emulate_step(regs, instr);
+	if (!stepped) {
+		for (i = 0; i < nr_wp_slots(); i++) {
+			if (!hit[i])
+				continue;
+			handler_error(bp[i], info[i]);
+			info[i] = NULL;
+		}
+		return false;
+	}
+	return true;
 }
 
 int hw_breakpoint_handler(struct die_args *args)
 {
+	bool err = false;
 	int rc = NOTIFY_STOP;
-	struct perf_event *bp;
+	struct perf_event *bp[HBP_NUM_MAX] = { NULL };
 	struct pt_regs *regs = args->regs;
-	struct arch_hw_breakpoint *info;
+	struct arch_hw_breakpoint *info[HBP_NUM_MAX] = { NULL };
+	int i;
+	int hit[HBP_NUM_MAX] = {0};
+	int nr_hit = 0;
+	bool ptrace_bp = false;
+	struct ppc_inst instr = ppc_inst(0);
+	int type = 0;
+	int size = 0;
+	bool larx_stcx = false;
 
 	/* Disable breakpoints during exception handling */
 	hw_breakpoint_disable();
@@ -317,12 +470,40 @@ int hw_breakpoint_handler(struct die_args *args)
 	 */
 	rcu_read_lock();
 
-	bp = __this_cpu_read(bp_per_reg);
-	if (!bp) {
+	if (!IS_ENABLED(CONFIG_PPC_8xx))
+		get_instr_detail(regs, &instr, &type, &size, &larx_stcx);
+
+	for (i = 0; i < nr_wp_slots(); i++) {
+		bp[i] = __this_cpu_read(bp_per_reg[i]);
+		if (!bp[i])
+			continue;
+
+		info[i] = counter_arch_bp(bp[i]);
+		info[i]->type &= ~HW_BRK_TYPE_EXTRANEOUS_IRQ;
+
+		if (check_constraints(regs, instr, type, size, info[i])) {
+			if (!IS_ENABLED(CONFIG_PPC_8xx) &&
+			    ppc_inst_equal(instr, ppc_inst(0))) {
+				handler_error(bp[i], info[i]);
+				info[i] = NULL;
+				err = 1;
+				continue;
+			}
+
+			if (is_ptrace_bp(bp[i]))
+				ptrace_bp = true;
+			hit[i] = 1;
+			nr_hit++;
+		}
+	}
+
+	if (err)
+		goto reset;
+
+	if (!nr_hit) {
 		rc = NOTIFY_DONE;
 		goto out;
 	}
-	info = counter_arch_bp(bp);
 
 	/*
 	 * Return early after invoking user-callback function without restoring
@@ -330,29 +511,50 @@ int hw_breakpoint_handler(struct die_args *args)
 	 * one-shot mode. The ptrace-ed process will receive the SIGTRAP signal
 	 * generated in do_dabr().
 	 */
-	if (is_ptrace_bp(bp)) {
-		perf_bp_event(bp, regs);
+	if (ptrace_bp) {
+		for (i = 0; i < nr_wp_slots(); i++) {
+			if (!hit[i])
+				continue;
+			perf_bp_event(bp[i], regs);
+			info[i] = NULL;
+		}
 		rc = NOTIFY_DONE;
-		goto out;
+		goto reset;
 	}
 
-	info->type &= ~HW_BRK_TYPE_EXTRANEOUS_IRQ;
-	if (IS_ENABLED(CONFIG_PPC_8xx)) {
-		if (!dar_within_range(regs->dar, info))
-			info->type |= HW_BRK_TYPE_EXTRANEOUS_IRQ;
-	} else {
-		if (!stepping_handler(regs, bp, info))
-			goto out;
+	if (!IS_ENABLED(CONFIG_PPC_8xx)) {
+		if (larx_stcx) {
+			for (i = 0; i < nr_wp_slots(); i++) {
+				if (!hit[i])
+					continue;
+				larx_stcx_err(bp[i], info[i]);
+				info[i] = NULL;
+			}
+			goto reset;
+		}
+
+		if (!stepping_handler(regs, bp, info, hit, instr))
+			goto reset;
 	}
 
 	/*
 	 * As a policy, the callback is invoked in a 'trigger-after-execute'
 	 * fashion
 	 */
-	if (!(info->type & HW_BRK_TYPE_EXTRANEOUS_IRQ))
-		perf_bp_event(bp, regs);
+	for (i = 0; i < nr_wp_slots(); i++) {
+		if (!hit[i])
+			continue;
+		if (!(info[i]->type & HW_BRK_TYPE_EXTRANEOUS_IRQ))
+			perf_bp_event(bp[i], regs);
+	}
+
+reset:
+	for (i = 0; i < nr_wp_slots(); i++) {
+		if (!info[i])
+			continue;
+		__set_breakpoint(i, info[i]);
+	}
 
-	__set_breakpoint(0, info);
 out:
 	rcu_read_unlock();
 	return rc;
@@ -367,26 +569,43 @@ static int single_step_dabr_instruction(struct die_args *args)
 	struct pt_regs *regs = args->regs;
 	struct perf_event *bp = NULL;
 	struct arch_hw_breakpoint *info;
+	int i;
+	bool found = false;
 
-	bp = current->thread.last_hit_ubp;
 	/*
 	 * Check if we are single-stepping as a result of a
 	 * previous HW Breakpoint exception
 	 */
-	if (!bp)
-		return NOTIFY_DONE;
+	for (i = 0; i < nr_wp_slots(); i++) {
+		bp = current->thread.last_hit_ubp[i];
+
+		if (!bp)
+			continue;
+
+		found = true;
+		info = counter_arch_bp(bp);
+
+		/*
+		 * We shall invoke the user-defined callback function in the
+		 * single stepping handler to confirm to 'trigger-after-execute'
+		 * semantics
+		 */
+		if (!(info->type & HW_BRK_TYPE_EXTRANEOUS_IRQ))
+			perf_bp_event(bp, regs);
+		current->thread.last_hit_ubp[i] = NULL;
+	}
 
-	info = counter_arch_bp(bp);
+	if (!found)
+		return NOTIFY_DONE;
 
-	/*
-	 * We shall invoke the user-defined callback function in the single
-	 * stepping handler to confirm to 'trigger-after-execute' semantics
-	 */
-	if (!(info->type & HW_BRK_TYPE_EXTRANEOUS_IRQ))
-		perf_bp_event(bp, regs);
+	for (i = 0; i < nr_wp_slots(); i++) {
+		bp = __this_cpu_read(bp_per_reg[i]);
+		if (!bp)
+			continue;
 
-	__set_breakpoint(0, info);
-	current->thread.last_hit_ubp = NULL;
+		info = counter_arch_bp(bp);
+		__set_breakpoint(i, info);
+	}
 
 	/*
 	 * If the process was being single-stepped by ptrace, let the
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 9b11575dcb8a..048d64c4e115 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -629,9 +629,6 @@ void do_break (struct pt_regs *regs, unsigned long address,
 	if (debugger_break_match(regs))
 		return;
 
-	/* Clear the breakpoint */
-	hw_breakpoint_disable();
-
 	/* Deliver the signal to userspace */
 	force_sig_fault(SIGTRAP, TRAP_HWBKPT, (void __user *)address);
 }