powerpc/inst: Add __copy_inst_from_kernel_nofault()

On the same model as get_user() versus __get_user(),
introduce __copy_inst_from_kernel_nofault() which doesn't
check address.

To be used by callers that have already checked that the adress
is a kernel address.
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/1f3702890d6dbd64702b61834753bcc96851c18c.1652074503.git.christophe.leroy@csgroup.eu

arch/powerpc/include/asm/inst.h

@@ -158,13 +158,10 @@ static inline char *__ppc_inst_as_str(char str[PPC_INST_STR_LEN], ppc_inst_t x)
 	__str;				\
 })
 
-static inline int copy_inst_from_kernel_nofault(ppc_inst_t *inst, u32 *src)
+static inline int __copy_inst_from_kernel_nofault(ppc_inst_t *inst, u32 *src)
 {
 	unsigned int val, suffix;
 
-	if (unlikely(!is_kernel_addr((unsigned long)src)))
-		return -ERANGE;
-
 /* See https://github.com/ClangBuiltLinux/linux/issues/1521 */
 #if defined(CONFIG_CC_IS_CLANG) && CONFIG_CLANG_VERSION < 140000
 	val = suffix = 0;
@@ -181,4 +178,12 @@ static inline int copy_inst_from_kernel_nofault(ppc_inst_t *inst, u32 *src)
 	return -EFAULT;
 }
 
+static inline int copy_inst_from_kernel_nofault(ppc_inst_t *inst, u32 *src)
+{
+	if (unlikely(!is_kernel_addr((unsigned long)src)))
+		return -ERANGE;
+
+	return __copy_inst_from_kernel_nofault(inst, src);
+}
+
 #endif /* _ASM_POWERPC_INST_H */