x86/build changes for v4.8

index 13f888a02a3d..385a5ef41c17 100644
@@ -47,6 +47,7 @@ This document describes the Linux kernel Makefiles.
 		--- 7.2 genhdr-y
 		--- 7.3 destination-y
 		--- 7.4 generic-y
+		--- 7.5 generated-y
 
 	=== 8 Kbuild Variables
 	=== 9 Makefile language

@@ -1319,6 +1320,19 @@ See subsequent chapter for the syntax of the Kbuild file.
 		Example: termios.h
 			#include <asm-generic/termios.h>
 
+	--- 7.5 generated-y
+
+	If an architecture generates other header files alongside generic-y
+	wrappers, and not included in genhdr-y, then generated-y specifies
+	them.
+
+	This prevents them being treated as stale asm-generic wrappers and
+	removed.
+
+		Example:
+			#arch/x86/include/asm/Kbuild
+			generated-y += syscalls_32.h
+
 === 8 Kbuild Variables
 
 The top Makefile exports the following variables:

index aeac434c9feb..2cfed174e3c9 100644
@@ -1,5 +1,11 @@
 
 
+generated-y += syscalls_32.h
+generated-y += syscalls_64.h
+generated-y += unistd_32_ia32.h
+generated-y += unistd_64_x32.h
+generated-y += xen-hypercalls.h
+
 genhdr-y += unistd_32.h
 genhdr-y += unistd_64.h
 genhdr-y += unistd_x32.h

index 045e0098e962..e4d017d53819 100644
@@ -13,11 +13,26 @@ include scripts/Kbuild.include
 # Create output directory if not already present
 _dummy := $(shell [ -d $(obj) ] || mkdir -p $(obj))
 
+# Stale wrappers when the corresponding files are removed from generic-y
+# need removing.
+generated-y   := $(generic-y) $(genhdr-y) $(generated-y)
+all-files     := $(patsubst %, $(obj)/%, $(generated-y))
+old-headers   := $(wildcard $(obj)/*.h)
+unwanted      := $(filter-out $(all-files),$(old-headers))
+
 quiet_cmd_wrap = WRAP    $@
 cmd_wrap = echo "\#include <asm-generic/$*.h>" >$@
 
-all: $(patsubst %, $(obj)/%, $(generic-y))
+quiet_cmd_remove = REMOVE  $(unwanted)
+cmd_remove = rm -f $(unwanted)
+
+all: $(patsubst %, $(obj)/%, $(generic-y)) FORCE
+	$(if $(unwanted),$(call cmd,remove),)
 	@:
 
 $(obj)/%.h:
 	$(call cmd,wrap)
+
+PHONY += FORCE
+.PHONY: $(PHONY)
+FORCE: ;