1 files changed, 50 insertions, 83 deletions

diff --git a/arch/powerpc/kernel/hw_breakpoint.c b/arch/powerpc/kernel/hw_breakpoint.c
index a293a53b4365..1007ec36b4cb 100644
--- a/arch/powerpc/kernel/hw_breakpoint.c
+++ b/arch/powerpc/kernel/hw_breakpoint.c
@@ -195,18 +195,63 @@ void thread_change_pc(struct task_struct *tsk, struct pt_regs *regs)
 	tsk->thread.last_hit_ubp = NULL;
 }
 
+static bool is_larx_stcx_instr(struct pt_regs *regs, unsigned int instr)
+{
+	int ret, type;
+	struct instruction_op op;
+
+	ret = analyse_instr(&op, regs, instr);
+	type = GETTYPE(op.type);
+	return (!ret && (type == LARX || type == STCX));
+}
+
 /*
  * Handle debug exception notifications.
  */
+static bool stepping_handler(struct pt_regs *regs, struct perf_event *bp,
+			     unsigned long addr)
+{
+	unsigned int instr = 0;
+
+	if (__get_user_inatomic(instr, (unsigned int *)regs->nip))
+		goto fail;
+
+	if (is_larx_stcx_instr(regs, instr)) {
+		printk_ratelimited("Breakpoint hit on instruction that can't be emulated."
+				   " Breakpoint at 0x%lx will be disabled.\n", addr);
+		goto disable;
+	}
+
+	/* Do not emulate user-space instructions, instead single-step them */
+	if (user_mode(regs)) {
+		current->thread.last_hit_ubp = bp;
+		regs->msr |= MSR_SE;
+		return false;
+	}
+
+	if (!emulate_step(regs, instr))
+		goto fail;
+
+	return true;
+
+fail:
+	/*
+	 * We've failed in reliably handling the hw-breakpoint. Unregister
+	 * it and throw a warning message to let the user know about it.
+	 */
+	WARN(1, "Unable to handle hardware breakpoint. Breakpoint at "
+		"0x%lx will be disabled.", addr);
+
+disable:
+	perf_event_disable_inatomic(bp);
+	return false;
+}
+
 int hw_breakpoint_handler(struct die_args *args)
 {
 	int rc = NOTIFY_STOP;
 	struct perf_event *bp;
 	struct pt_regs *regs = args->regs;
-#ifndef CONFIG_PPC_8xx
-	int stepped = 1;
-	unsigned int instr;
-#endif
 	struct arch_hw_breakpoint *info;
 	unsigned long dar = regs->dar;
 
@@ -251,31 +296,9 @@ int hw_breakpoint_handler(struct die_args *args)
 	      (dar - bp->attr.bp_addr < bp->attr.bp_len)))
 		info->type |= HW_BRK_TYPE_EXTRANEOUS_IRQ;
 
-#ifndef CONFIG_PPC_8xx
-	/* 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 (!IS_ENABLED(CONFIG_PPC_8xx) && !stepping_handler(regs, bp, info->address))
 		goto out;
-	}
 
-	stepped = 0;
-	instr = 0;
-	if (!__get_user_inatomic(instr, (unsigned int *) regs->nip))
-		stepped = emulate_step(regs, instr);
-
-	/*
-	 * emulate_step() could not execute it. We've failed in reliably
-	 * handling the hw-breakpoint. Unregister it and throw a warning
-	 * message to let the user know about it.
-	 */
-	if (!stepped) {
-		WARN(1, "Unable to handle hardware breakpoint. Breakpoint at "
-			"0x%lx will be disabled.", info->address);
-		perf_event_disable_inatomic(bp);
-		goto out;
-	}
-#endif
 	/*
 	 * As a policy, the callback is invoked in a 'trigger-after-execute'
 	 * fashion
@@ -366,59 +389,3 @@ void hw_breakpoint_pmu_read(struct perf_event *bp)
 {
 	/* TODO */
 }
-
-bool dawr_force_enable;
-EXPORT_SYMBOL_GPL(dawr_force_enable);
-
-static ssize_t dawr_write_file_bool(struct file *file,
-				    const char __user *user_buf,
-				    size_t count, loff_t *ppos)
-{
-	struct arch_hw_breakpoint null_brk = {0, 0, 0};
-	size_t rc;
-
-	/* Send error to user if they hypervisor won't allow us to write DAWR */
-	if ((!dawr_force_enable) &&
-	    (firmware_has_feature(FW_FEATURE_LPAR)) &&
-	    (set_dawr(&null_brk) != H_SUCCESS))
-		return -1;
-
-	rc = debugfs_write_file_bool(file, user_buf, count, ppos);
-	if (rc)
-		return rc;
-
-	/* If we are clearing, make sure all CPUs have the DAWR cleared */
-	if (!dawr_force_enable)
-		smp_call_function((smp_call_func_t)set_dawr, &null_brk, 0);
-
-	return rc;
-}
-
-static const struct file_operations dawr_enable_fops = {
-	.read =		debugfs_read_file_bool,
-	.write =	dawr_write_file_bool,
-	.open =		simple_open,
-	.llseek =	default_llseek,
-};
-
-static int __init dawr_force_setup(void)
-{
-	dawr_force_enable = false;
-
-	if (cpu_has_feature(CPU_FTR_DAWR)) {
-		/* Don't setup sysfs file for user control on P8 */
-		dawr_force_enable = true;
-		return 0;
-	}
-
-	if (PVR_VER(mfspr(SPRN_PVR)) == PVR_POWER9) {
-		/* Turn DAWR off by default, but allow admin to turn it on */
-		dawr_force_enable = false;
-		debugfs_create_file_unsafe("dawr_enable_dangerous", 0600,
-					   powerpc_debugfs_root,
-					   &dawr_force_enable,
-					   &dawr_enable_fops);
-	}
-	return 0;
-}
-arch_initcall(dawr_force_setup);