malloc: Provide posix_memalign() implementation.

ext2progs library really wants a working version of this,
and thankfully it's not that hard to do.

With help from Richard Mortimer.

Reported-by: Alex Buell <alex.buell@munted.org.uk>
Tested-by: Alex Buell <alex.buell@munted.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 31 insertions, 7 deletions

diff --git a/common/malloc.c b/common/malloc.c
index cc3946d..94fc29c 100644
--- a/common/malloc.c
+++ b/common/malloc.c
@@ -27,6 +27,12 @@ static char *malloc_ptr = (char *) MALLOC_BASE;
 
 static char *last_alloc = 0;
 
+static char *align_ptr_to(char *ptr, unsigned long align)
+{
+    return (char *) ((((unsigned long) ptr) + (align - 1UL)) &
+		     ~(align - 1UL));
+}
+
 void *malloc (int size)
 {
     char *caddr;
@@ -34,10 +40,34 @@ void *malloc (int size)
     caddr = malloc_ptr;
     malloc_ptr += size;
     last_alloc = caddr;
-    malloc_ptr = (char *) ((((unsigned long) malloc_ptr) + 7) & (~7));
+    malloc_ptr = align_ptr_to(malloc_ptr, 8UL);
     return caddr;
 }
 
+int posix_memalign(void **memptr, unsigned long alignment, unsigned long size)
+{
+    char *caddr;
+
+    if (alignment & (alignment - 1UL))
+        return -1;
+    if (alignment & (sizeof(void *) - 1UL))
+        return -1;
+
+    if (size == 0) {
+      *memptr = (void *) 0;
+      return 0;
+    }
+
+    caddr = align_ptr_to(malloc_ptr, alignment);
+    malloc_ptr = (caddr + size);
+    last_alloc = caddr;
+    malloc_ptr = align_ptr_to(malloc_ptr, 8UL);
+
+    *memptr = caddr;
+
+    return 0;
+}
+
 void free (void *m)
 {
     if (m == last_alloc)
diff --git a/second/fs/ext2.c b/second/fs/ext2.c
index 12d00dc..57f5e9a 100644
--- a/second/fs/ext2.c
+++ b/second/fs/ext2.c
@@ -163,9 +163,3 @@ void *realloc(void *p, int size)
 {
         return NULL;
 }
-
-int posix_memalign(void **memptr, size_t alignment, size_t size)
-{
-	*memptr = NULL;
-	return -1;
-}