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-rw-r--r--mm/maccess.c62
1 files changed, 62 insertions, 0 deletions
diff --git a/mm/maccess.c b/mm/maccess.c
new file mode 100644
index 00000000..4cee182a
--- /dev/null
+++ b/mm/maccess.c
@@ -0,0 +1,62 @@
+/*
+ * Access kernel memory without faulting.
+ */
+#include <linux/module.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);