warn about use of uninstalled kernel headers

User applications frequently hit problems when they try to use
the kernel headers directly, rather than the exported headers.

This adds an explicit warning for this case, and points to
a URL holding an explanation of why this is wrong and what
to do about it.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index d3cd23f3003962de7d50219b1967a87e37f9d364..f4e3184fa0540724d7777d0f140fc189cd806941 100644 (file)
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -659,6 +659,12 @@ extern int do_sysinfo(struct sysinfo *info);
 
 #endif /* __KERNEL__ */
 
+#ifndef __EXPORTED_HEADERS__
+#ifndef __KERNEL__
+#warning Attempt to use kernel headers from user space, see http://kernelnewbies.org/KernelHeaders
+#endif /* __KERNEL__ */
+#endif /* __EXPORTED_HEADERS__ */
+
 #define SI_LOAD_SHIFT  16
 struct sysinfo {
        long uptime;                    /* Seconds since boot */

diff --git a/scripts/headers_install.pl b/scripts/headers_install.pl
index c6ae4052ab43bb5b8a884c23923d59ebf49de8ec..b89ca2c58fdbbe3592f97a27592675417713653c 100644 (file)
--- a/scripts/headers_install.pl
+++ b/scripts/headers_install.pl
@@ -20,7 +20,7 @@ use strict;
 
 my ($readdir, $installdir, $arch, @files) = @ARGV;
 
-my $unifdef = "scripts/unifdef -U__KERNEL__";
+my $unifdef = "scripts/unifdef -U__KERNEL__ -D__EXPORTED_HEADERS__";
 
 foreach my $file (@files) {
        local *INFILE;