um: disable scan_elf_aux() on x86_64

Reusing the host's vDSO makes only sense on x86_32.
Signed-off-by: NRichard Weinberger <richard@nod.at>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

arch/um/os-Linux/Makefile

@@ -3,10 +3,12 @@
 # Licensed under the GPL
 #
 
-obj-y = aio.o elf_aux.o execvp.o file.o helper.o irq.o main.o mem.o process.o \
+obj-y = aio.o execvp.o file.o helper.o irq.o main.o mem.o process.o \
 	registers.o sigio.o signal.o start_up.o time.o tty.o uaccess.o \
 	umid.o tls.o user_syms.o util.o drivers/ sys-$(SUBARCH)/ skas/
 
+obj-$(CONFIG_ARCH_REUSE_HOST_VSYSCALL_AREA) += elf_aux.o
+
 USER_OBJS := $(user-objs-y) aio.o elf_aux.o execvp.o file.o helper.o irq.o \
 	main.o mem.o process.o registers.o sigio.o signal.o start_up.o time.o \
 	tty.o tls.o uaccess.o umid.o util.o

arch/um/os-Linux/elf_aux.c

@@ -14,16 +14,11 @@
 #include "mem_user.h"
 #include <kern_constants.h>
 
-/* Use the one from the kernel - the host may miss it, if having old headers. */
-#if UM_ELF_CLASS == UM_ELFCLASS32
 typedef Elf32_auxv_t elf_auxv_t;
-#else
-typedef Elf64_auxv_t elf_auxv_t;
-#endif
 
 /* These are initialized very early in boot and never changed */
 char * elf_aux_platform;
-long elf_aux_hwcap;
+extern long elf_aux_hwcap;
 unsigned long vsyscall_ehdr;
 unsigned long vsyscall_end;
 unsigned long __kernel_vsyscall;

arch/um/os-Linux/main.c

@@ -21,6 +21,8 @@
 #define STACKSIZE (8 * 1024 * 1024)
 #define THREAD_NAME_LEN (256)
 
+long elf_aux_hwcap;
+
 static void set_stklim(void)
 {
 	struct rlimit lim;
@@ -143,7 +145,9 @@ int __init main(int argc, char **argv, char **envp)
 	install_fatal_handler(SIGINT);
 	install_fatal_handler(SIGTERM);
 
+#ifdef CONFIG_ARCH_REUSE_HOST_VSYSCALL_AREA
 	scan_elf_aux(envp);
+#endif
 
 	do_uml_initcalls();
 	ret = linux_main(argc, argv);