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SubjectRe: userspace mptable parsing broken in 2.6
Dave Jones wrote:

>Reading from some parts of /dev/mem is still broken in 2.6.3rc2,
>which breaks at least x86info.
>
>Manfred, in the end of the last thread on this at..
>http://www.ussg.iu.edu/hypermail/linux/kernel/0311.1/0373.html
>you mentioned you were going to add some code to /dev/mem for the
>DEBUG_PAGEALLOC case. Did you get anywhere with that?
>
>
Sorry, I forgot about the issue.

What about the attached patch?

--
Manfred
--- 2.6/drivers/char/mem.c 2004-02-08 13:08:30.000000000 +0100
+++ build-2.6/drivers/char/mem.c 2004-02-12 20:10:56.000000000 +0100
@@ -25,6 +25,7 @@
#include <linux/devfs_fs_kernel.h>
#include <linux/ptrace.h>
#include <linux/device.h>
+#include <linux/pagemap.h>

#include <asm/uaccess.h>
#include <asm/io.h>
@@ -151,10 +152,41 @@
}
}
#endif
+#if CONFIG_DEBUG_PAGEALLOC
+ while (count) {
+ size_t i;
+ struct page *page;
+
+ i = PAGE_SIZE - (p%PAGE_SIZE);
+ if (i > count)
+ i = count;
+ if (virt_addr_valid(__va(p))) {
+ page = virt_to_page(__va(p));
+ get_page(page);
+ kernel_map_pages(page, 1, 1);
+ } else {
+ page = NULL;
+ }
+ if (copy_to_user(buf, __va(p), i)) {
+ if (page)
+ put_page(page);
+ return -EFAULT;
+ }
+ if (page)
+ put_page(page);
+ buf += i;
+ p += i;
+ count -= i;
+ read += i;
+ }
+#else
if (copy_to_user(buf, __va(p), count))
return -EFAULT;
+
+ p += count;
read += count;
- *ppos += read;
+#endif
+ *ppos = p;
return read;
}
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