Re: [BUG?] x86_64 : Can not read /dev/kmem ?

[Andi Kleen]

On Mon, Mar 14, 2005 at 11:37:19AM +0100, Eric Dumazet wrote:
> 
> Hi Andi
> 
> I tried to mmap /dev/kmem on x86_64 (linux-2.6.11) and got no success.
> 

Here's a patch that fixes the problem to me.


Fix mmap of /dev/kmem. It cannot ever have worked before.

vmalloc is still not supported because that would be more
complicated.

Signed-off-by: Andi Kleen <ak@xxxxxxx>


diff -u linux-2.6.11/drivers/char/mem.c-o linux-2.6.11/drivers/char/mem.c
--- linux-2.6.11/drivers/char/mem.c-o	2004-12-24 22:34:47.000000000 +0100
+++ linux-2.6.11/drivers/char/mem.c	2005-03-22 12:36:33.852319000 +0100
@@ -211,6 +211,23 @@
 	return 0;
 }
 
+static int mmap_kmem(struct file * file, struct vm_area_struct * vma)
+{
+        unsigned long long val;
+	/* 
+	 * RED-PEN: on some architectures there is more mapped memory
+	 * than available in mem_map which pfn_valid checks
+	 * for. Perhaps should add a new macro here.
+	 * 
+	 * RED-PEN: vmalloc is not supported right now. 
+	 */
+	if (!pfn_valid(vma->vm_pgoff))
+		return -EIO;
+	val = (u64)vma->vm_pgoff << PAGE_SHIFT;
+	vma->vm_pgoff = __pa(val) >> PAGE_SHIFT; 
+	return mmap_mem(file, vma);
+}
+
 extern long vread(char *buf, char *addr, unsigned long count);
 extern long vwrite(char *buf, char *addr, unsigned long count);
 
@@ -567,7 +584,6 @@
 	return capable(CAP_SYS_RAWIO) ? 0 : -EPERM;
 }
 
-#define mmap_kmem	mmap_mem
 #define zero_lseek	null_lseek
 #define full_lseek      null_lseek
 #define write_zero	write_null
-
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