[PATCH] lib: fwts_mmap: add fwts_page_size()

[Colin King]

From: Colin Ian King <colin.king at canonical.com>

Add a helper function fwts_page_size() to determine the system
page size.  Default to 4096 if sysconf() does not help us.

Signed-off-by: Colin Ian King <colin.king at canonical.com>
---
 src/lib/include/fwts_mmap.h |    2 ++
 src/lib/src/fwts_mmap.c     |   25 ++++++++++++++++++-------
 2 files changed, 20 insertions(+), 7 deletions(-)

diff --git a/src/lib/include/fwts_mmap.h b/src/lib/include/fwts_mmap.h
index 62d8f1c..4a76489 100644
--- a/src/lib/include/fwts_mmap.h
+++ b/src/lib/include/fwts_mmap.h
@@ -20,8 +20,10 @@
 #ifndef __FWTS_MMAP_H__
 #define __FWTS_MMAP_H__
 
+#include <stddef.h>
 #include <sys/mman.h>
 
+const size_t fwts_page_size(void);
 void *fwts_mmap(const off_t start, const size_t size);
 int fwts_munmap(void *mem, const size_t size);
 
diff --git a/src/lib/src/fwts_mmap.c b/src/lib/src/fwts_mmap.c
index c47960d..cee0854 100644
--- a/src/lib/src/fwts_mmap.c
+++ b/src/lib/src/fwts_mmap.c
@@ -24,7 +24,22 @@
 
 #include "fwts.h"
 
-#define PAGE_SIZE	4096
+#define FWTS_DEFAULT_PAGE_SIZE  (4096)
+
+/*
+ *  fwts_page_size()
+ *	determine system page size, guess if we can't
+ *	get it from sysconf().
+ */
+const size_t fwts_page_size(void)
+{
+	size_t page_size;
+
+	page_size = sysconf(_SC_PAGESIZE);
+
+	/* If sysconf() returns -1, default it 4K */
+	return page_size == -1 ? FWTS_DEFAULT_PAGE_SIZE : page_size;
+}
 
 /*
  *  fwts_mmap()
@@ -40,9 +55,7 @@ void *fwts_mmap(const off_t start, const size_t size)
 	void *mem;
 	void *ret = FWTS_MAP_FAILED;
 
- 	if ((page_size = sysconf(_SC_PAGE_SIZE)) == -1)
-		page_size = PAGE_SIZE;	/* Guess */
-
+	page_size = fwts_page_size();
 	offset = ((size_t)start) & (page_size - 1);
 	length = (size_t)size + offset;
 
@@ -66,9 +79,7 @@ int fwts_munmap(void *mem, const size_t size)
 	int page_size;
 	off_t offset;
 
- 	if ((page_size = sysconf(_SC_PAGE_SIZE)) == -1)
-		page_size = PAGE_SIZE;	/* Guess */
-
+	page_size = fwts_page_size();
 	offset = ((off_t)(mem)) & (page_size - 1);
 
 	if (munmap(mem - offset, size + offset) < 0)
-- 
1.7.10.4