[Xen-devel] [PATCH] libxc: mmap doesn't return NULL on error...

[Rusty Russell <rusty@xxxxxxxxxxxxxxx>]

Hi, was reading libxc code, and noticed this.  Patch is bigger than
strictly necessary due to indent adjust.

Against latest bk.
Rusty.

diff -urpN --exclude TAGS -X 
/home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal 
base/tools/libxc/xc.h working/tools/libxc/xc.h
--- base/tools/libxc/xc.h       2005-05-12 11:06:44.306151968 +1000
+++ working/tools/libxc/xc.h    2005-05-12 11:10:25.821476520 +1000
@@ -421,7 +421,7 @@ int xc_msr_write(int xc_handle, int cpu_
 /**
  * Memory maps a range within one domain to a local address range.  Mappings
  * should be unmapped with munmap and should follow the same rules as mmap
- * regarding page alignment.
+ * regarding page alignment.  Returns NULL on failure.
  *
  * In Linux, the ring queue for the control channel is accessible by mapping
  * the shared_info_frame (from xc_domain_getinfo()) + 2048.  The structure
diff -urpN --exclude TAGS -X 
/home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal 
base/tools/libxc/xc_private.c working/tools/libxc/xc_private.c
--- base/tools/libxc/xc_private.c       2005-05-12 11:06:44.924058032 +1000
+++ working/tools/libxc/xc_private.c    2005-05-12 11:10:03.195916128 +1000
@@ -13,18 +13,18 @@ void *xc_map_foreign_batch(int xc_handle
     privcmd_mmapbatch_t ioctlx; 
     void *addr;
     addr = mmap(NULL, num*PAGE_SIZE, prot, MAP_SHARED, xc_handle, 0);
-    if ( addr != NULL )
+    if ( addr == MAP_FAILED )
+       return NULL;
+
+    ioctlx.num=num;
+    ioctlx.dom=dom;
+    ioctlx.addr=(unsigned long)addr;
+    ioctlx.arr=arr;
+    if ( ioctl( xc_handle, IOCTL_PRIVCMD_MMAPBATCH, &ioctlx ) < 0 )
     {
-        ioctlx.num=num;
-        ioctlx.dom=dom;
-        ioctlx.addr=(unsigned long)addr;
-        ioctlx.arr=arr;
-        if ( ioctl( xc_handle, IOCTL_PRIVCMD_MMAPBATCH, &ioctlx ) < 0 )
-        {
-            perror("XXXXXXXX");
-            munmap(addr, num*PAGE_SIZE);
-            return 0;
-        }
+       perror("XXXXXXXX");
+       munmap(addr, num*PAGE_SIZE);
+       return NULL;
     }
     return addr;
 
@@ -40,19 +40,19 @@ void *xc_map_foreign_range(int xc_handle
     privcmd_mmap_entry_t entry; 
     void *addr;
     addr = mmap(NULL, size, prot, MAP_SHARED, xc_handle, 0);
-    if ( addr != NULL )
+    if ( addr == MAP_FAILED )
+       return NULL;
+
+    ioctlx.num=1;
+    ioctlx.dom=dom;
+    ioctlx.entry=&entry;
+    entry.va=(unsigned long) addr;
+    entry.mfn=mfn;
+    entry.npages=(size+PAGE_SIZE-1)>>PAGE_SHIFT;
+    if ( ioctl( xc_handle, IOCTL_PRIVCMD_MMAP, &ioctlx ) < 0 )
     {
-        ioctlx.num=1;
-        ioctlx.dom=dom;
-        ioctlx.entry=&entry;
-        entry.va=(unsigned long) addr;
-        entry.mfn=mfn;
-        entry.npages=(size+PAGE_SIZE-1)>>PAGE_SHIFT;
-        if ( ioctl( xc_handle, IOCTL_PRIVCMD_MMAP, &ioctlx ) < 0 )
-        {
-            munmap(addr, size);
-            return 0;
-        }
+       munmap(addr, size);
+       return NULL;
     }
     return addr;
 }

-- 
A bad analogy is like a leaky screwdriver -- Richard Braakman


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