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From: Wu Fengguang on 30 Jan 2010 04:40
When /dev/kmem read()/write() encounters hwpoison page, stop it
and return the amount of work done till now, or return -EIO if
nothing have been copied.

For simplicity, hwpoison pages accessed by vmalloc address are
siliently skipped, instead of returning -EIO.

CC: Greg KH <greg(a)kroah.com>
CC: Andi Kleen <andi(a)firstfloor.org>
CC: Benjamin Herrenschmidt <benh(a)kernel.crashing.org>
CC: Christoph Lameter <cl(a)linux-foundation.org>
CC: Ingo Molnar <mingo(a)elte.hu>
CC: Tejun Heo <tj(a)kernel.org>
CC: Nick Piggin <npiggin(a)suse.de>
CC: KAMEZAWA Hiroyuki <kamezawa.hiroyu(a)jp.fujitsu.com>
Signed-off-by: Wu Fengguang <fengguang.wu(a)intel.com>
---
drivers/char/mem.c | 18 ++++++++++++++----
mm/vmalloc.c | 4 ++--
2 files changed, 16 insertions(+), 6 deletions(-)

--- linux-mm.orig/drivers/char/mem.c 2010-01-30 17:14:12.000000000 +0800
+++ linux-mm/drivers/char/mem.c 2010-01-30 17:20:18.000000000 +0800
@@ -426,6 +426,9 @@ static ssize_t read_kmem(struct file *fi
*/
kbuf = xlate_dev_kmem_ptr((char *)p);

+ if (unlikely(virt_addr_valid(kbuf) &&
+ PageHWPoison(virt_to_page(kbuf))))
+ return -EIO;
if (copy_to_user(buf, kbuf, sz))
return -EFAULT;
buf += sz;
@@ -471,6 +474,7 @@ do_write_kmem(unsigned long p, const cha
{
ssize_t written, sz;
unsigned long copied;
+ int err = 0;

written = 0;
#ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
@@ -497,13 +501,19 @@ do_write_kmem(unsigned long p, const cha
*/
ptr = xlate_dev_kmem_ptr((char *)p);

+ if (unlikely(virt_addr_valid(ptr) &&
+ PageHWPoison(virt_to_page(ptr)))) {
+ err = -EIO;
+ break;
+ }
+
copied = copy_from_user(ptr, buf, sz);
if (copied) {
written += sz - copied;
- if (written)
- break;
- return -EFAULT;
+ err = -EFAULT;
+ break;
}
+
buf += sz;
p += sz;
count -= sz;
@@ -511,7 +521,7 @@ do_write_kmem(unsigned long p, const cha
}

*ppos += written;
- return written;
+ return written ? written : err;
}


--- linux-mm.orig/mm/vmalloc.c 2010-01-30 17:14:15.000000000 +0800
+++ linux-mm/mm/vmalloc.c 2010-01-30 17:20:18.000000000 +0800
@@ -1669,7 +1669,7 @@ static int aligned_vread(char *buf, char
* interface, rarely used. Instead of that, we'll use
* kmap() and get small overhead in this access function.
*/
- if (p) {
+ if (p && !PageHWPoison(p)) {
/*
* we can expect USER0 is not used (see vread/vwrite's
* function description)
@@ -1708,7 +1708,7 @@ static int aligned_vwrite(char *buf, cha
* interface, rarely used. Instead of that, we'll use
* kmap() and get small overhead in this access function.
*/
- if (p) {
+ if (p && !PageHWPoison(p)) {
/*
* we can expect USER0 is not used (see vread/vwrite's
* function description)


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Prev: [PATCH 0/4] hwpoison checks for /dev/mem etc.
Next: [PATCH 4/4] hwpoison: avoid "still referenced by -1 users" warning