From 708e57b3257251b7d26327d993dd03ceec553978 Mon Sep 17 00:00:00 2001
From: Sascha Wildner <saw@online.de>
Date: Mon, 17 Aug 2015 19:23:18 +0200
Subject: [PATCH] kernel/vmm: Untangle a too deeply nested if/else.

Get rid of if/goto/else cases. Check errors first and return early where
possible.
---
 sys/platform/pc64/vmm/vmm_utils.c | 101 +++++++++++++++---------------
 1 file changed, 51 insertions(+), 50 deletions(-)

diff --git a/sys/platform/pc64/vmm/vmm_utils.c b/sys/platform/pc64/vmm/vmm_utils.c
index 9e65f29d06..362d01a08d 100644
--- a/sys/platform/pc64/vmm/vmm_utils.c
+++ b/sys/platform/pc64/vmm/vmm_utils.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2003-2013 The DragonFly Project.  All rights reserved.
+ * Copyright (c) 2013 The DragonFly Project.  All rights reserved.
  *
  * This code is derived from software contributed to The DragonFly Project
  * by Mihai Carabas <mihai.carabas@gmail.com>
@@ -44,7 +44,6 @@
 int
 instr_check(struct instr_decode *instr, void *ip, uint8_t instr_length)
 {
-
 	uint8_t i;
 	uint8_t *instr_ip;
 	uint8_t *instr_opcode;
@@ -97,7 +96,8 @@ error:
 }
 
 int
-guest_phys_addr(struct vmspace *vm, register_t *gpa, register_t guest_cr3, vm_offset_t uaddr)
+guest_phys_addr(struct vmspace *vm, register_t *gpa, register_t guest_cr3,
+    vm_offset_t uaddr)
 {
 	pt_entry_t pml4e;
 	pt_entry_t pdpe;
@@ -110,57 +110,58 @@ guest_phys_addr(struct vmspace *vm, register_t *gpa, register_t guest_cr3, vm_of
 		kprintf("%s: could not get pml4e\n", __func__);
 		goto error;
 	}
-	if (pml4e & kernel_pmap.pmap_bits[PG_V_IDX]) {
-		err = get_pt_entry(vm, &pdpe, pml4e & PG_FRAME, (uaddr & PML4MASK) >> PDPSHIFT);
-		if (err) {
-			kprintf("%s: could not get pdpe\n", __func__);
-			goto error;
-		}
-		if (pdpe & kernel_pmap.pmap_bits[PG_V_IDX]) {
-			if (pdpe & kernel_pmap.pmap_bits[PG_PS_IDX]) {
-				*gpa = (pdpe & PG_FRAME) | (uaddr & PDPMASK);
-				goto out;
-			} else {
-				err = get_pt_entry(vm, &pde, pdpe & PG_FRAME, (uaddr & PDPMASK) >> PDRSHIFT);
-				if(err) {
-					kprintf("%s: could not get pdpe\n", __func__);
-					goto error;
-				}
-				if (pde & kernel_pmap.pmap_bits[PG_V_IDX]) {
-					if (pde & kernel_pmap.pmap_bits[PG_PS_IDX]) {
-						*gpa = (pde & PG_FRAME) | (uaddr & PDRMASK);
-						goto out;
-					} else {
-						err = get_pt_entry(vm, &pte, pde & PG_FRAME, (uaddr & PDRMASK) >> PAGE_SHIFT);
-						if (err) {
-							kprintf("%s: could not get pte\n", __func__);
-							goto error;
-						}
-						if (pte & kernel_pmap.pmap_bits[PG_V_IDX]) {
-							*gpa = (pte & PG_FRAME) | (uaddr & PAGE_MASK);
-						} else {
-							kprintf("%s: pte not valid\n", __func__);
-							err = EFAULT;
-							goto error;
-						}
-					}
-				} else {
-					kprintf("%s: pde not valid\n", __func__);
-					err = EFAULT;
-					goto error;
-				}
-			}
-		} else {
-			kprintf("%s: pdpe not valid\n", __func__);
-			err = EFAULT;
-			goto error;
-		}
-	} else {
+	if (!(pml4e & kernel_pmap.pmap_bits[PG_V_IDX])) {
 		kprintf("%s: pml4e not valid\n", __func__);
 		err = EFAULT;
 		goto error;
 	}
-out:
+
+	err = get_pt_entry(vm, &pdpe, pml4e & PG_FRAME,
+	    (uaddr & PML4MASK) >> PDPSHIFT);
+	if (err) {
+		kprintf("%s: could not get pdpe\n", __func__);
+		goto error;
+	}
+	if (!(pdpe & kernel_pmap.pmap_bits[PG_V_IDX])) {
+		kprintf("%s: pdpe not valid\n", __func__);
+		err = EFAULT;
+		goto error;
+	}
+	if (pdpe & kernel_pmap.pmap_bits[PG_PS_IDX]) {
+		*gpa = (pdpe & PG_FRAME) | (uaddr & PDPMASK);
+		return 0;
+	}
+
+	err = get_pt_entry(vm, &pde, pdpe & PG_FRAME,
+	    (uaddr & PDPMASK) >> PDRSHIFT);
+	if (err) {
+		kprintf("%s: could not get pdpe\n", __func__);
+		goto error;
+	}
+	if (!(pde & kernel_pmap.pmap_bits[PG_V_IDX])) {
+		kprintf("%s: pde not valid\n", __func__);
+		err = EFAULT;
+		goto error;
+	}
+	if (pde & kernel_pmap.pmap_bits[PG_PS_IDX]) {
+		*gpa = (pde & PG_FRAME) | (uaddr & PDRMASK);
+		return 0;
+	}
+
+	err = get_pt_entry(vm, &pte, pde & PG_FRAME,
+	    (uaddr & PDRMASK) >> PAGE_SHIFT);
+	if (err) {
+		kprintf("%s: could not get pte\n", __func__);
+		goto error;
+	}
+	if (!(pte & kernel_pmap.pmap_bits[PG_V_IDX])) {
+		kprintf("%s: pte not valid\n", __func__);
+		err = EFAULT;
+		goto error;
+	}
+	*gpa = (pte & PG_FRAME) | (uaddr & PAGE_MASK);
+	return 0;
+
 error:
 	return err;
 }
-- 
2.41.0