Add the rt linux 4.1.3-rt3 as base

[kvmfornfv.git] / kernel / mm / maccess.c

diff --git a/kernel/mm/maccess.c b/kernel/mm/maccess.c
new file mode 100644 (file)
index 0000000..d53adf9
--- /dev/null
+++ b/kernel/mm/maccess.c
@@ -0,0 +1,62 @@
+/*
+ * Access kernel memory without faulting.
+ */
+#include <linux/export.h>
+#include <linux/mm.h>
+#include <linux/uaccess.h>
+
+/**
+ * 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.
+ */
+
+long __weak probe_kernel_read(void *dst, const void *src, size_t size)
+    __attribute__((alias("__probe_kernel_read")));
+
+long __probe_kernel_read(void *dst, const void *src, size_t size)
+{
+       long ret;
+       mm_segment_t old_fs = get_fs();
+
+       set_fs(KERNEL_DS);
+       pagefault_disable();
+       ret = __copy_from_user_inatomic(dst,
+                       (__force const void __user *)src, size);
+       pagefault_enable();
+       set_fs(old_fs);
+
+       return ret ? -EFAULT : 0;
+}
+EXPORT_SYMBOL_GPL(probe_kernel_read);
+
+/**
+ * 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.
+ */
+long __weak probe_kernel_write(void *dst, const void *src, size_t size)
+    __attribute__((alias("__probe_kernel_write")));
+
+long __probe_kernel_write(void *dst, const void *src, size_t size)
+{
+       long ret;
+       mm_segment_t old_fs = get_fs();
+
+       set_fs(KERNEL_DS);
+       pagefault_disable();
+       ret = __copy_to_user_inatomic((__force void __user *)dst, src, size);
+       pagefault_enable();
+       set_fs(old_fs);
+
+       return ret ? -EFAULT : 0;
+}
+EXPORT_SYMBOL_GPL(probe_kernel_write);