[PATCH 19/23] x86: use non-set_fs based maccess routines

Christoph Hellwig
2020-05-21T15:24:48Z

Provide arch_kernel_read and arch_kernel_write routines to implement the
maccess routines without messing with set_fs and without stac/clac that
opens up access to user space.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
arch/x86/include/asm/uaccess.h | 16 ++++++++++++++++
1 file changed, 16 insertions(+)

diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index d8f283b9a569c..b3e0a56ae961a 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -523,5 +523,21 @@ do { \
unsafe_copy_loop(__ucu_dst, __ucu_src, __ucu_len, u8, label); \
} while (0)

+#define HAVE_GET_KERNEL_NOFAULT
+
+#define __get_kernel_nofault(dst, src, type, err_label) \
+do { \
+ int __kr_err; \
+ \
+ __get_user_size(*((type *)dst), (__force type __user *)src, \
+ sizeof(type), __kr_err); \
+ if (unlikely(__kr_err)) \
+ goto err_label; \
+} while (0)
+
+#define __put_kernel_nofault(dst, src, type, err_label) \
+ __put_user_size(*((type *)(src)), (__force type __user *)(dst), \
+ sizeof(type), err_label)
+
#endif /* _ASM_X86_UACCESS_H */

--
2.26.2