powerpc/uaccess: Add unsafe_copy_from_user()

Use the same approach as unsafe_copy_to_user() but instead call
unsafe_get_user() in a loop.

Signed-off-by: Christopher M. Riedl <cmr@codefail.de>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210227011259.11992-2-cmr@codefail.de

diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h
index 479cb30..c3d3d17 100644 (file)
--- a/arch/powerpc/include/asm/uaccess.h
+++ b/arch/powerpc/include/asm/uaccess.h
@@ -486,6 +486,27 @@ user_write_access_begin(const void __user *ptr, size_t len)
 #define unsafe_put_user(x, p, e) \
        __unsafe_put_user_goto((__typeof__(*(p)))(x), (p), sizeof(*(p)), e)
 
+#define unsafe_copy_from_user(d, s, l, e) \
+do {                                                                                   \
+       u8 *_dst = (u8 *)(d);                                                           \
+       const u8 __user *_src = (const u8 __user *)(s);                                 \
+       size_t _len = (l);                                                              \
+       int _i;                                                                         \
+                                                                                       \
+       for (_i = 0; _i < (_len & ~(sizeof(long) - 1)); _i += sizeof(long))             \
+               unsafe_get_user(*(long *)(_dst + _i), (long __user *)(_src + _i), e);   \
+       if (IS_ENABLED(CONFIG_PPC64) && (_len & 4)) {                                   \
+               unsafe_get_user(*(u32 *)(_dst + _i), (u32 __user *)(_src + _i), e);     \
+               _i += 4;                                                                \
+       }                                                                               \
+       if (_len & 2) {                                                                 \
+               unsafe_get_user(*(u16 *)(_dst + _i), (u16 __user *)(_src + _i), e);     \
+               _i += 2;                                                                \
+       }                                                                               \
+       if (_len & 1)                                                                   \
+               unsafe_get_user(*(u8 *)(_dst + _i), (u8 __user *)(_src + _i), e);       \
+} while (0)
+
 #define unsafe_copy_to_user(d, s, l, e) \
 do {                                                                   \
        u8 __user *_dst = (u8 __user *)(d);                             \