/dev/mem: introduce size_inside_page()

Introduce size_inside_page() to replace duplicate /dev/mem code.

Also apply it to /dev/kmem, whose alignment logic was buggy.

Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Acked-by: Andi Kleen <ak@linux.intel.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Greg Kroah-Hartman <gregkh@suse.de>
Cc: Mark Brown <broonie@opensource.wolfsonmicro.com>
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: Avi Kivity <avi@qumranet.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 19 insertions, 41 deletions

diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index f0a90590cb1a..aaa9c24d4c14 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -34,6 +34,19 @@
 # include <linux/efi.h>
 #endif
 
+static inline unsigned long size_inside_page(unsigned long start,
+                                             unsigned long size)
+{
+        unsigned long sz;
+
+        if (-start & (PAGE_SIZE - 1))
+                sz = -start & (PAGE_SIZE - 1);
+        else
+                sz = PAGE_SIZE;
+
+        return min_t(unsigned long, sz, size);
+}
+
 /*
  * Architectures vary in how they handle caching for addresses
  * outside of main memory.
@@ -141,15 +154,7 @@ static ssize_t read_mem(struct file * file, char __user * buf,
 #endif
 
         while (count > 0) {
-                /*
-                 * Handle first page in case it's not aligned
-                 */
-                if (-p & (PAGE_SIZE - 1))
-                        sz = -p & (PAGE_SIZE - 1);
-                else
-                        sz = PAGE_SIZE;
-
-                sz = min_t(unsigned long, sz, count);
+                sz = size_inside_page(p, count);
 
                 if (!range_is_allowed(p >> PAGE_SHIFT, count))
                         return -EPERM;
@@ -208,15 +213,7 @@ static ssize_t write_mem(struct file * file, const char __user * buf,
 #endif
 
         while (count > 0) {
-                /*
-                 * Handle first page in case it's not aligned
-                 */
-                if (-p & (PAGE_SIZE - 1))
-                        sz = -p & (PAGE_SIZE - 1);
-                else
-                        sz = PAGE_SIZE;
-
-                sz = min_t(unsigned long, sz, count);
+                sz = size_inside_page(p, count);
 
                 if (!range_is_allowed(p >> PAGE_SHIFT, sz))
                         return -EPERM;
@@ -429,15 +426,7 @@ static ssize_t read_kmem(struct file *file, char __user *buf,
                 }
 #endif
                 while (low_count > 0) {
-                        /*
-                         * Handle first page in case it's not aligned
-                         */
-                        if (-p & (PAGE_SIZE - 1))
-                                sz = -p & (PAGE_SIZE - 1);
-                        else
-                                sz = PAGE_SIZE;
-
-                        sz = min_t(unsigned long, sz, low_count);
+                        sz = size_inside_page(p, low_count);
 
                         /*
                          * On ia64 if a page has been mapped somewhere as
@@ -461,10 +450,8 @@ static ssize_t read_kmem(struct file *file, char __user *buf,
                 if (!kbuf)
                         return -ENOMEM;
                 while (count > 0) {
-                        int len = count;
+                        int len = size_inside_page(p, count);
 
-                        if (len > PAGE_SIZE)
-                                len = PAGE_SIZE;
                         len = vread(kbuf, (char *)p, len);
                         if (!len)
                                 break;
@@ -509,15 +496,8 @@ do_write_kmem(void *p, unsigned long realp, const char __user * buf,
 
         while (count > 0) {
                 char *ptr;
-                /*
-                 * Handle first page in case it's not aligned
-                 */
-                if (-realp & (PAGE_SIZE - 1))
-                        sz = -realp & (PAGE_SIZE - 1);
-                else
-                        sz = PAGE_SIZE;
 
-                sz = min_t(unsigned long, sz, count);
+                sz = size_inside_page(realp, count);
 
                 /*
                  * On ia64 if a page has been mapped somewhere as
@@ -577,10 +557,8 @@ static ssize_t write_kmem(struct file * file, const char __user * buf,
                 if (!kbuf)
                         return wrote ? wrote : -ENOMEM;
                 while (count > 0) {
-                        int len = count;
+                        int len = size_inside_page(p, count);
 
-                        if (len > PAGE_SIZE)
-                                len = PAGE_SIZE;
                         written = copy_from_user(kbuf, buf, len);
                         if (written) {
                                 if (wrote + virtr)