From 57f0f512b273f60d52568b8c6b77e17f5636edc0 Mon Sep 17 00:00:00 2001
From: André Fabian Silva Delgado <emulatorman@parabola.nu>
Date: Wed, 5 Aug 2015 17:04:01 -0300
Subject: Initial import

---
 include/linux/uaccess.h | 110 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 110 insertions(+)
 create mode 100644 include/linux/uaccess.h

(limited to 'include/linux/uaccess.h')

diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h
new file mode 100644
index 000000000..ecd3319da
--- /dev/null
+++ b/include/linux/uaccess.h
@@ -0,0 +1,110 @@
+#ifndef __LINUX_UACCESS_H__
+#define __LINUX_UACCESS_H__
+
+#include <linux/preempt.h>
+#include <asm/uaccess.h>
+
+/*
+ * These routines enable/disable the pagefault handler in that
+ * it will not take any locks and go straight to the fixup table.
+ *
+ * They have great resemblance to the preempt_disable/enable calls
+ * and in fact they are identical; this is because currently there is
+ * no other way to make the pagefault handlers do this. So we do
+ * disable preemption but we don't necessarily care about that.
+ */
+static inline void pagefault_disable(void)
+{
+	preempt_count_inc();
+	/*
+	 * make sure to have issued the store before a pagefault
+	 * can hit.
+	 */
+	barrier();
+}
+
+static inline void pagefault_enable(void)
+{
+#ifndef CONFIG_PREEMPT
+	/*
+	 * make sure to issue those last loads/stores before enabling
+	 * the pagefault handler again.
+	 */
+	barrier();
+	preempt_count_dec();
+#else
+	preempt_enable();
+#endif
+}
+
+#ifndef ARCH_HAS_NOCACHE_UACCESS
+
+static inline unsigned long __copy_from_user_inatomic_nocache(void *to,
+				const void __user *from, unsigned long n)
+{
+	return __copy_from_user_inatomic(to, from, n);
+}
+
+static inline unsigned long __copy_from_user_nocache(void *to,
+				const void __user *from, unsigned long n)
+{
+	return __copy_from_user(to, from, n);
+}
+
+#endif		/* ARCH_HAS_NOCACHE_UACCESS */
+
+/**
+ * probe_kernel_address(): safely attempt to read from a location
+ * @addr: address to read from - its type is type typeof(retval)*
+ * @retval: read into this variable
+ *
+ * Safely read from address @addr into variable @revtal.  If a kernel fault
+ * happens, handle that and return -EFAULT.
+ * We ensure that the __get_user() is executed in atomic context so that
+ * do_page_fault() doesn't attempt to take mmap_sem.  This makes
+ * probe_kernel_address() suitable for use within regions where the caller
+ * already holds mmap_sem, or other locks which nest inside mmap_sem.
+ * This must be a macro because __get_user() needs to know the types of the
+ * args.
+ *
+ * We don't include enough header files to be able to do the set_fs().  We
+ * require that the probe_kernel_address() caller will do that.
+ */
+#define probe_kernel_address(addr, retval)		\
+	({						\
+		long ret;				\
+		mm_segment_t old_fs = get_fs();		\
+							\
+		set_fs(KERNEL_DS);			\
+		pagefault_disable();			\
+		ret = __copy_from_user_inatomic(&(retval), (__force typeof(retval) __user *)(addr), sizeof(retval));		\
+		pagefault_enable();			\
+		set_fs(old_fs);				\
+		ret;					\
+	})
+
+/*
+ * probe_kernel_read(): safely attempt to read from a location
+ * @dst: pointer to the buffer that shall take the data
+ * @src: address to read from
+ * @size: size of the data chunk
+ *
+ * Safely read from address @src to the buffer at @dst.  If a kernel fault
+ * happens, handle that and return -EFAULT.
+ */
+extern long probe_kernel_read(void *dst, const void *src, size_t size);
+extern long __probe_kernel_read(void *dst, const void *src, size_t size);
+
+/*
+ * probe_kernel_write(): safely attempt to write to a location
+ * @dst: address to write to
+ * @src: pointer to the data that shall be written
+ * @size: size of the data chunk
+ *
+ * Safely write to address @dst from the buffer at @src.  If a kernel fault
+ * happens, handle that and return -EFAULT.
+ */
+extern long notrace probe_kernel_write(void *dst, const void *src, size_t size);
+extern long notrace __probe_kernel_write(void *dst, const void *src, size_t size);
+
+#endif		/* __LINUX_UACCESS_H__ */
-- 
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