From 61751a896bbba472c0bfa671cef6c9420e30028d Mon Sep 17 00:00:00 2001
From: Bahadir Balban <bbalban@b-labs.co.uk>
Date: Fri, 7 Nov 2008 20:13:28 +0200
Subject: [PATCH] vma_intersect() was erroneous, replaced by a nice and simple
 set_intersection() routine.

Still testing sys_munmap(). It now correctly spots and unmaps the overlapping vma.
The issue now is that if a split occurs, we forgot to add same objects to new vma.
---
 include/l4/lib/math.h       | 15 +++++++++++++++
 tasks/mm0/include/vm_area.h |  2 --
 tasks/mm0/src/mmap.c        | 23 ++++++-----------------
 tasks/mm0/src/munmap.c      |  4 +++-
 4 files changed, 24 insertions(+), 20 deletions(-)

diff --git a/include/l4/lib/math.h b/include/l4/lib/math.h
index fd12c08..d5ce96e 100644
--- a/include/l4/lib/math.h
+++ b/include/l4/lib/math.h
@@ -4,4 +4,19 @@
 #define min(x, y)		(((x) < (y)) ? x : y)
 #define max(x, y)		(((x) > (y)) ? x : y)
 
+/* Tests if ranges a-b intersect with range c-d */
+static inline int set_intersection(unsigned long a, unsigned long b,
+				   unsigned long c, unsigned long d)
+{
+	/*
+	 * Below is the complement (') of the intersection
+	 * of 2 ranges, much simpler ;-)
+	 */
+	if (b <= c || a >= d)
+		return 0;
+
+	/* The rest is always intersecting */
+	return 1;
+}
+
 #endif /* __LIB_MATH_H__ */
diff --git a/tasks/mm0/include/vm_area.h b/tasks/mm0/include/vm_area.h
index 47f6dc2..afdb753 100644
--- a/tasks/mm0/include/vm_area.h
+++ b/tasks/mm0/include/vm_area.h
@@ -183,8 +183,6 @@ struct vm_area {
 	unsigned long file_offset;	/* File offset in pfns */
 };
 
-int vma_intersect(unsigned long pfn_start, unsigned long pfn_end,
-		      struct vm_area *vma);
 /*
  * Finds the vma that has the given address.
  * TODO: In the future a lot of use cases may need to traverse each vma
diff --git a/tasks/mm0/src/mmap.c b/tasks/mm0/src/mmap.c
index 3cece38..6cdbea9 100644
--- a/tasks/mm0/src/mmap.c
+++ b/tasks/mm0/src/mmap.c
@@ -3,6 +3,7 @@
  *
  * Copyright (C) 2007, 2008 Bahadir Balban
  */
+#include <l4/lib/math.h>
 #include <vm_area.h>
 #include <kmalloc/kmalloc.h>
 #include INC_API(errno.h)
@@ -37,20 +38,6 @@ struct vm_area *vma_new(unsigned long pfn_start, unsigned long npages,
 	return vma;
 }
 
-int vma_intersect(unsigned long pfn_start, unsigned long pfn_end,
-		      struct vm_area *vma)
-{
-	if ((pfn_start <= vma->pfn_start) && (pfn_end > vma->pfn_start)) {
-		printf("%s: VMAs overlap.\n", __FUNCTION__);
-		return 1;
-	}
-	if ((pfn_end >= vma->pfn_end) && (pfn_start < vma->pfn_end)) {
-		printf("%s: VMAs overlap.\n", __FUNCTION__);
-		return 1;
-	}
-	return 0;
-}
-
 /* Search an empty space in the task's mmapable address region. */
 unsigned long find_unmapped_area(unsigned long npages, struct tcb *task)
 {
@@ -72,7 +59,8 @@ unsigned long find_unmapped_area(unsigned long npages, struct tcb *task)
 	while (pfn_end <= __pfn(task->end)) {
 
 		/* If intersection, skip the vma and fast-forward to next */
-		if (vma_intersect(pfn_start, pfn_end, vma)) {
+		if (set_intersection(pfn_start, pfn_end,
+				     vma->pfn_start, vma->pfn_end)) {
 
 			/* Update interval to next available space */
 			pfn_start = vma->pfn_end;
@@ -204,8 +192,9 @@ void *do_mmap(struct vm_file *mapfile, unsigned long file_offset,
 		 * splitting, shrink/grow etc.
 		 */
 		list_for_each_entry(mapped, &task->vm_area_head->list, list)
-			BUG_ON(vma_intersect(map_pfn, map_pfn + npages,
-					     mapped));
+			BUG_ON(set_intersection(map_pfn, map_pfn + npages,
+						mapped->pfn_start,
+						mapped->pfn_end));
 	}
 
 	/* For valid regions that aren't allocated by us, create the vma. */
diff --git a/tasks/mm0/src/munmap.c b/tasks/mm0/src/munmap.c
index 780289d..da2dfdd 100644
--- a/tasks/mm0/src/munmap.c
+++ b/tasks/mm0/src/munmap.c
@@ -6,6 +6,7 @@
 #include <mmap.h>
 #include <file.h>
 #include <l4/api/errno.h>
+#include <l4/lib/math.h>
 #include <l4lib/arch/syslib.h>
 
 
@@ -134,7 +135,8 @@ int do_munmap(struct tcb *task, void *vaddr, unsigned long npages)
 
 	list_for_each_entry_safe(vma, n, &task->vm_area_head->list, list) {
 		/* Check for intersection */
-		if (vma_intersect(munmap_start, munmap_end, vma)) {
+		if (set_intersection(munmap_start, munmap_end,
+				     vma->pfn_start, vma->pfn_end)) {
 			/*
 			 * Flush pages if vma is writable,
 			 * dirty and file-backed.