1 files changed, 59 insertions, 36 deletions

diff --git a/arch/x86/kernel/hw_breakpoint.c b/arch/x86/kernel/hw_breakpoint.c
index a8f1b803d2fd..02f07634d265 100644
--- a/arch/x86/kernel/hw_breakpoint.c
+++ b/arch/x86/kernel/hw_breakpoint.c
@@ -122,7 +122,7 @@ int arch_install_hw_breakpoint(struct perf_event *bp)
 		return -EBUSY;
 
 	set_debugreg(info->address, i);
-	__get_cpu_var(cpu_debugreg[i]) = info->address;
+	__this_cpu_write(cpu_debugreg[i], info->address);
 
 	dr7 = &__get_cpu_var(cpu_dr7);
 	*dr7 |= encode_dr7(i, info->len, info->type);
@@ -206,6 +206,25 @@ int arch_check_bp_in_kernelspace(struct perf_event *bp)
 int arch_bp_generic_fields(int x86_len, int x86_type,
 			   int *gen_len, int *gen_type)
 {
+	/* Type */
+	switch (x86_type) {
+	case X86_BREAKPOINT_EXECUTE:
+		if (x86_len != X86_BREAKPOINT_LEN_X)
+			return -EINVAL;
+
+		*gen_type = HW_BREAKPOINT_X;
+		*gen_len = sizeof(long);
+		return 0;
+	case X86_BREAKPOINT_WRITE:
+		*gen_type = HW_BREAKPOINT_W;
+		break;
+	case X86_BREAKPOINT_RW:
+		*gen_type = HW_BREAKPOINT_W | HW_BREAKPOINT_R;
+		break;
+	default:
+		return -EINVAL;
+	}
+
 	/* Len */
 	switch (x86_len) {
 	case X86_BREAKPOINT_LEN_1:
@@ -226,21 +245,6 @@ int arch_bp_generic_fields(int x86_len, int x86_type,
 		return -EINVAL;
 	}
 
-	/* Type */
-	switch (x86_type) {
-	case X86_BREAKPOINT_EXECUTE:
-		*gen_type = HW_BREAKPOINT_X;
-		break;
-	case X86_BREAKPOINT_WRITE:
-		*gen_type = HW_BREAKPOINT_W;
-		break;
-	case X86_BREAKPOINT_RW:
-		*gen_type = HW_BREAKPOINT_W | HW_BREAKPOINT_R;
-		break;
-	default:
-		return -EINVAL;
-	}
-
 	return 0;
 }
 
@@ -251,6 +255,29 @@ static int arch_build_bp_info(struct perf_event *bp)
 
 	info->address = bp->attr.bp_addr;
 
+	/* Type */
+	switch (bp->attr.bp_type) {
+	case HW_BREAKPOINT_W:
+		info->type = X86_BREAKPOINT_WRITE;
+		break;
+	case HW_BREAKPOINT_W | HW_BREAKPOINT_R:
+		info->type = X86_BREAKPOINT_RW;
+		break;
+	case HW_BREAKPOINT_X:
+		info->type = X86_BREAKPOINT_EXECUTE;
+		/*
+		 * x86 inst breakpoints need to have a specific undefined len.
+		 * But we still need to check userspace is not trying to setup
+		 * an unsupported length, to get a range breakpoint for example.
+		 */
+		if (bp->attr.bp_len == sizeof(long)) {
+			info->len = X86_BREAKPOINT_LEN_X;
+			return 0;
+		}
+	default:
+		return -EINVAL;
+	}
+
 	/* Len */
 	switch (bp->attr.bp_len) {
 	case HW_BREAKPOINT_LEN_1:
@@ -271,21 +298,6 @@ static int arch_build_bp_info(struct perf_event *bp)
 		return -EINVAL;
 	}
 
-	/* Type */
-	switch (bp->attr.bp_type) {
-	case HW_BREAKPOINT_W:
-		info->type = X86_BREAKPOINT_WRITE;
-		break;
-	case HW_BREAKPOINT_W | HW_BREAKPOINT_R:
-		info->type = X86_BREAKPOINT_RW;
-		break;
-	case HW_BREAKPOINT_X:
-		info->type = X86_BREAKPOINT_EXECUTE;
-		break;
-	default:
-		return -EINVAL;
-	}
-
 	return 0;
 }
 /*
@@ -385,12 +397,12 @@ void flush_ptrace_hw_breakpoint(struct task_struct *tsk)
 
 void hw_breakpoint_restore(void)
 {
-	set_debugreg(__get_cpu_var(cpu_debugreg[0]), 0);
-	set_debugreg(__get_cpu_var(cpu_debugreg[1]), 1);
-	set_debugreg(__get_cpu_var(cpu_debugreg[2]), 2);
-	set_debugreg(__get_cpu_var(cpu_debugreg[3]), 3);
+	set_debugreg(__this_cpu_read(cpu_debugreg[0]), 0);
+	set_debugreg(__this_cpu_read(cpu_debugreg[1]), 1);
+	set_debugreg(__this_cpu_read(cpu_debugreg[2]), 2);
+	set_debugreg(__this_cpu_read(cpu_debugreg[3]), 3);
 	set_debugreg(current->thread.debugreg6, 6);
-	set_debugreg(__get_cpu_var(cpu_dr7), 7);
+	set_debugreg(__this_cpu_read(cpu_dr7), 7);
 }
 EXPORT_SYMBOL_GPL(hw_breakpoint_restore);
 
@@ -421,6 +433,10 @@ static int __kprobes hw_breakpoint_handler(struct die_args *args)
 	dr6_p = (unsigned long *)ERR_PTR(args->err);
 	dr6 = *dr6_p;
 
+	/* If it's a single step, TRAP bits are random */
+	if (dr6 & DR_STEP)
+		return NOTIFY_DONE;
+
 	/* Do an early return if no trap bits are set in DR6 */
 	if ((dr6 & DR_TRAP_BITS) == 0)
 		return NOTIFY_DONE;
@@ -466,6 +482,13 @@ static int __kprobes hw_breakpoint_handler(struct die_args *args)
 
 		perf_bp_event(bp, args->regs);
 
+		/*
+		 * Set up resume flag to avoid breakpoint recursion when
+		 * returning back to origin.
+		 */
+		if (bp->hw.info.type == X86_BREAKPOINT_EXECUTE)
+			args->regs->flags |= X86_EFLAGS_RF;
+
 		rcu_read_unlock();
 	}
 	/*