[PATCH] uml: fix linkage of tt mode against NPTL

With Al Viro <viro@parcelfarce.linux.theplanet.co.uk>

To make sure switcheroo() can execute when we remap all the executable
image, we used a trick to make it use a local copy of errno...  this trick
does not work with NPTL glibc, only with LinuxThreads, so use another
(simpler) one to make it work anyway.

Hopefully, a lot improved thanks to merging with the version of Al Viro
(which had his part of problems, though, i.e.  removing a fix to another
bug and not fixing the problem on i386).

Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 27 insertions, 0 deletions

diff --git a/arch/um/sys-i386/Makefile b/arch/um/sys-i386/Makefile
index 4351e5605506..095bcdb0b9cc 100644
--- a/arch/um/sys-i386/Makefile
+++ b/arch/um/sys-i386/Makefile
@@ -17,3 +17,5 @@ highmem.c-dir = mm
 module.c-dir = kernel
 
 subdir- := util
+
+include arch/um/scripts/Makefile.unmap
diff --git a/arch/um/sys-i386/unmap.c b/arch/um/sys-i386/unmap.c
new file mode 100644
index 000000000000..136875263d27
--- /dev/null
+++ b/arch/um/sys-i386/unmap.c
@@ -0,0 +1,25 @@
+/*
+ * Copyright (C) 2000 Jeff Dike (jdike@karaya.com)
+ * Licensed under the GPL
+ */
+
+#include <linux/mman.h>
+#include <asm/unistd.h>
+
+static int errno;
+
+static inline _syscall2(int,munmap,void *,start,size_t,len)
+static inline _syscall6(void *,mmap2,void *,addr,size_t,len,int,prot,int,flags,int,fd,off_t,offset)
+int switcheroo(int fd, int prot, void *from, void *to, int size)
+{
+	if(munmap(to, size) < 0){
+		return(-1);
+	}
+	if(mmap2(to, size, prot, MAP_SHARED | MAP_FIXED, fd, 0) != to){
+		return(-1);
+	}
+	if(munmap(from, size) < 0){
+		return(-1);
+	}
+	return(0);
+}