powerpc: Move copy_from_kernel_nofault_inst()

When probe_kernel_read_inst() was created, there was no good place to
put it, so a file called lib/inst.c was dedicated for it.

Since then, probe_kernel_read_inst() has been renamed
copy_from_kernel_nofault_inst(). And mm/maccess.h didn't exist at that
time. Today, mm/maccess.h is related to copy_from_kernel_nofault().

Move copy_from_kernel_nofault_inst() into mm/maccess.c

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>

arch/powerpc/mm/maccess.c

@@ -3,7 +3,28 @@
 #include <linux/uaccess.h>
 #include <linux/kernel.h>
 
+#include <asm/disassemble.h>
+#include <asm/inst.h>
+#include <asm/ppc-opcode.h>
+
 bool copy_from_kernel_nofault_allowed(const void *unsafe_src, size_t size)
 {
 	return is_kernel_addr((unsigned long)unsafe_src);
 }
+
+int copy_from_kernel_nofault_inst(struct ppc_inst *inst, struct ppc_inst *src)
+{
+	unsigned int val, suffix;
+	int err;
+
+	err = copy_from_kernel_nofault(&val, src, sizeof(val));
+	if (err)
+		return err;
+	if (IS_ENABLED(CONFIG_PPC64) && get_op(val) == OP_PREFIX) {
+		err = copy_from_kernel_nofault(&suffix, (void *)src + 4, 4);
+		*inst = ppc_inst_prefix(val, suffix);
+	} else {
+		*inst = ppc_inst(val);
+	}
+	return err;
+}