linux-kernel - [2/6] uaccess: add probe_kernel

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Date:	Sun, 10 Feb 2008 08:13:26 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	linux-kernel@...r.kernel.org
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@....com.au>,
	Thomas Gleixner <tglx@...utronix.de>,
	Jason Wessel <jason.wessel@...driver.com>
Subject: [2/6] uaccess: add probe_kernel_write()

From: Ingo Molnar <mingo@...e.hu>

add probe_kernel_write() - copy & paste of the existing
probe_kernel_access(), extended to writes.

Signed-off-by: Ingo Molnar <mingo@...e.hu>
Reviewed-by: Thomas Gleixner <tglx@...utronix.de>
---
 include/linux/uaccess.h |   22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

Index: linux-kgdb.q/include/linux/uaccess.h
===================================================================
--- linux-kgdb.q.orig/include/linux/uaccess.h
+++ linux-kgdb.q/include/linux/uaccess.h
@@ -84,4 +84,26 @@ static inline unsigned long __copy_from_
 		ret;					\
 	})
 
+/**
+ * probe_kernel_write(): safely attempt to write to a location
+ * @addr: address to write to - its type is type typeof(rdval)*
+ * @rdval: write to this variable
+ *
+ * Safely write to address @addr from variable @rdval.  If a kernel fault
+ * happens, handle that and return -EFAULT.
+ */
+#define probe_kernel_write(addr, rdval)			\
+	({						\
+		long ret;				\
+		mm_segment_t old_fs = get_fs();		\
+							\
+		set_fs(KERNEL_DS);			\
+		pagefault_disable();			\
+		ret = __put_user(rdval,			\
+	 (__force typeof(rdval) __user *)(addr));	\
+		pagefault_enable();			\
+		set_fs(old_fs);				\
+		ret;					\
+	})
+
 #endif		/* __LINUX_UACCESS_H__ */
--
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