x86, um: get rid of arch/um/os symlink

we can get DEV_NULL defined for arch/um/drivers/null.c in less
convoluted ways, TYVM...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

arch/um/Makefile

@@ -18,12 +18,9 @@ core-y			+= $(ARCH_DIR)/kernel/		\
 			   $(ARCH_DIR)/drivers/		\
 			   $(ARCH_DIR)/os-$(OS)/
 
-# XXX: The "os" symlink is only used by arch/um/include/os.h, which includes
-# ../os/include/file.h
-#
 # These are cleaned up during mrproper. Please DO NOT fix it again, this is
 # the Correct Thing(tm) to do!
-ARCH_SYMLINKS = $(ARCH_DIR)/os $(ARCH_DIR)/include/shared/uml-config.h
+ARCH_SYMLINKS = $(ARCH_DIR)/include/shared/uml-config.h
 
 MODE_INCLUDE	+= -I$(srctree)/$(ARCH_DIR)/include/shared/skas
 
@@ -143,14 +140,6 @@ $(objtree)/$(ARCH_DIR)/include/shared:
 	@echo '  MKDIR $@'
 	$(Q)mkdir -p $@
 
-$(ARCH_DIR)/os:
-	@echo '  SYMLINK $@'
-ifneq ($(KBUILD_SRC),)
-	$(Q)ln -fsn $(srctree)/$(ARCH_DIR)/os-$(OS) $@
-else
-	$(Q)ln -fsn os-$(OS) $@
-endif
-
 # Generated files
 define filechk_umlconfig
 	sed 's/ CONFIG/ UML_CONFIG/'
@@ -182,4 +171,4 @@ $(ARCH_DIR)/include/shared/kern_constants.h: $(objtree)/$(ARCH_DIR)/include/shar
 	@echo '  SYMLINK $@'
 	$(Q)ln -sf ../../../../include/asm/asm-offsets.h $@
 
-export SUBARCH USER_CFLAGS CFLAGS_NO_HARDENING OS HEADER_ARCH
+export SUBARCH USER_CFLAGS CFLAGS_NO_HARDENING OS HEADER_ARCH DEV_NULL_PATH

arch/um/Makefile-os-Linux

@@ -6,3 +6,4 @@
 # To get a definition of F_SETSIG
 USER_CFLAGS += -D_GNU_SOURCE -D_LARGEFILE64_SOURCE
 KBUILD_CFLAGS += -D_LARGEFILE64_SOURCE
+DEV_NULL_PATH = \"/dev/null\"

arch/um/drivers/Makefile

@@ -62,5 +62,6 @@ obj-$(CONFIG_UML_RANDOM) += random.o
 
 # pcap_user.o must be added explicitly.
 USER_OBJS := fd.o null.o pty.o tty.o xterm.o slip_common.o pcap_user.o vde_user.o
+CFLAGS_null.o = -DDEV_NULL=$(DEV_NULL_PATH)
 
 include arch/um/scripts/Makefile.rules

arch/um/include/shared/os.h

@@ -11,7 +11,6 @@
 #include "longjmp.h"
 #include "mm_id.h"
 #include "sysdep/tls.h"
-#include "../../os/include/file.h"
 
 #define CATCH_EINTR(expr) while ((errno = 0, ((expr) < 0)) && (errno == EINTR))
 

arch/um/os-Linux/include/file.h

-/* 
- * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
- * Licensed under the GPL
- */
-
-#ifndef __OS_FILE_H__
-#define __OS_FILE_H__
-
-#define DEV_NULL "/dev/null"
-
-#endif