Re: [linux-next:master 3983/4215] fs/proc/page.c:453:8: note: in expansion of macro 'get_user'

[Vladimir Davydov <vdavydov@parallels.com>]

On Fri, Jul 24, 2015 at 02:43:07PM +0800, kbuild test robot wrote:

>    In file included from include/linux/linkage.h:4:0,
>                     from include/linux/preempt.h:9,
>                     from include/linux/spinlock.h:50,
>                     from include/linux/mmzone.h:7,
>                     from include/linux/bootmem.h:7,
>                     from fs/proc/page.c:1:
>    fs/proc/page.c: In function 'kpageidle_write':
> >> include/linux/compiler.h:447:38: error: call to '__compiletime_assert_453' declared with attribute error: BUILD_BUG failed
>      _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
>                                          ^
>    include/linux/compiler.h:430:4: note: in definition of macro '__compiletime_assert'
>        prefix ## suffix();    \
>        ^
>    include/linux/compiler.h:447:2: note: in expansion of macro '_compiletime_assert'
>      _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
>      ^
>    include/linux/bug.h:50:37: note: in expansion of macro 'compiletime_assert'
>     #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
>                                         ^
>    include/linux/bug.h:84:21: note: in expansion of macro 'BUILD_BUG_ON_MSG'
>     #define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed")
>                         ^
> >> arch/parisc/include/asm/uaccess.h:43:26: note: in expansion of macro 'BUILD_BUG'
>     #define LDD_KERNEL(ptr)  BUILD_BUG()
>                              ^
> >> arch/parisc/include/asm/uaccess.h:93:14: note: in expansion of macro 'LDD_KERNEL'
>          case 8: LDD_KERNEL(ptr); break;   \
>                  ^
> >> arch/parisc/include/asm/uaccess.h:40:18: note: in expansion of macro '__get_user'
>     #define get_user __get_user
>                      ^
> >> fs/proc/page.c:453:8: note: in expansion of macro 'get_user'
>        if (get_user(idle_bitmap, in)) {

The following patch should fix this issue, as well as another
kbuild-test-robot report:

  [linux-next:master 3983/4215] fs/proc/page.o:undefined reference to `__user_bad'

From: Vladimir Davydov <vdavydov@parallels.com>
Subject: [PATCH] proc: kpageidle_write: use copy_from_user instead of get_user

Not all architectures support 8-byte get_user.

Fixes: proc-add-kpageidle-file
Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>

diff --git a/fs/proc/page.c b/fs/proc/page.c
index 9daa6e92450f..4191ddb79b84 100644
--- a/fs/proc/page.c
+++ b/fs/proc/page.c
@@ -464,7 +464,7 @@ static ssize_t kpageidle_write(struct file *file, const char __user *buf,
 	for (; pfn < end_pfn; pfn++) {
 		bit = pfn % KPMBITS;
 		if (bit == 0) {
-			if (get_user(idle_bitmap, in)) {
+			if (copy_from_user(&idle_bitmap, in, sizeof(u64))) {
 				ret = -EFAULT;
 				break;
 			}

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