x86/power/64: Use char arrays for asm function names

This switches the hibernate_64.S function names into character arrays
to match other areas of the kernel where this is done (e.g., linker
scripts). Specifically this fixes a compile-time error noticed by the
future CONFIG_FORTIFY_SOURCE routines that complained about PAGE_SIZE
being copied out of the "single byte" core_restore_code variable.

Additionally drops the "acpi_save_state_mem" exern which does not
appear to be used anywhere else in the kernel.
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

arch/x86/include/asm/suspend_64.h

@@ -42,8 +42,7 @@ struct saved_context {
 	set_debugreg((thread)->debugreg##register, register)
 
 /* routines for saving/restoring kernel state */
-extern int acpi_save_state_mem(void);
-extern char core_restore_code;
-extern char restore_registers;
+extern char core_restore_code[];
+extern char restore_registers[];
 
 #endif /* _ASM_X86_SUSPEND_64_H */

arch/x86/power/hibernate_64.c

@@ -147,7 +147,7 @@ static int relocate_restore_code(void)
 	if (!relocated_restore_code)
 		return -ENOMEM;
 
-	memcpy((void *)relocated_restore_code, &core_restore_code, PAGE_SIZE);
+	memcpy((void *)relocated_restore_code, core_restore_code, PAGE_SIZE);
 
 	/* Make the page containing the relocated code executable */
 	pgd = (pgd_t *)__va(read_cr3()) + pgd_index(relocated_restore_code);
@@ -292,8 +292,8 @@ int arch_hibernation_header_save(void *addr, unsigned int max_size)
 
 	if (max_size < sizeof(struct restore_data_record))
 		return -EOVERFLOW;
-	rdr->jump_address = (unsigned long)&restore_registers;
-	rdr->jump_address_phys = __pa_symbol(&restore_registers);
+	rdr->jump_address = (unsigned long)restore_registers;
+	rdr->jump_address_phys = __pa_symbol(restore_registers);
 	rdr->cr3 = restore_cr3;
 	rdr->magic = RESTORE_MAGIC;