Build shadow header files when necessary on Linux

The current kernel module build infrastructure relies on the ability to
create symlinks from known directory names used in the AFS code to the
actual locations of the kernel header files.  This breaks if there is no
single kernel header tree and instead multiple trees are layered together
by kbuild using compile-time -I include paths.

Attempt to detect this case by seeing if linux/types.h is in the kernel
header directory where we expect it.  If not, rather than creating
symlinks for h, sys, and netinet, create directories and populate them
with single-line headers that just include the corresponding linux/*.h
header.  The list of headers for which to do this is generated dynamically
by analyzing the AFS kernel source code and looking for relevant #include
directives.

This patch has been part of the Debian OpenAFS package since
1.4.10+dfsg1-1.  The check for whether we have layered kernel header trees
may be specific to Debian and may require modification later if other
Linux distributions do something similar.

FIXES 124583

Reviewed-on: http://gerrit.openafs.org/6
Verified-by: Russ Allbery <rra@stanford.edu>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Verified-by: Derrick Brashear <shadow@dementia.org>
(cherry picked from commit 01d390d0d022309d06760aac1373829a35a6d79c)
Change-Id: I5a5ba79e88f8aafc07502c7d1c82058184c01da0
Reviewed-on: http://gerrit.openafs.org/775
Tested-by: Russ Allbery <rra@stanford.edu>

diff --git a/src/libafs/make_kbuild_makefile.pl b/src/libafs/make_kbuild_makefile.pl
index dd10db1e327f637d251575ece4bc612b8c164c27..7f73a761d93608973580661d41865d3295401a8d 100755 (executable)
--- a/src/libafs/make_kbuild_makefile.pl
+++ b/src/libafs/make_kbuild_makefile.pl
@@ -90,12 +90,61 @@ foreach (@objects) {
   symlink($deps{$_}, "$KDIR/$src") or die "$KDIR/$src: $!\n";
 }
 
-foreach $src (qw(h sys netinet)) {
-  if (-e "$KDIR/$src" || -l "$KDIR/$src") {
-    unlink("$KDIR/$src") or die "$KDIR/$src: $!\n";
+%remap = ('h' => 'linux', 'netinet' => 'linux', 'sys' => 'linux');
+if (-f "$vars{LINUX_KERNEL_PATH}/include/linux/types.h") {
+  foreach $src (keys %remap) {
+    if (-e "$KDIR/$src" || -l "$KDIR/$src") {
+      unlink("$KDIR/$src") or die "$KDIR/$src: $!\n";
+    }
+    symlink("$vars{LINUX_KERNEL_PATH}/include/linux", "$KDIR/$src")
+      or die "$KDIR/$src: $!\n";
+  }
+} else {
+  foreach $src (keys %remap) {
+    system ('rm', '-rf', "$KDIR/$src"); # too crude?
+    mkdir("$KDIR/$src", 0777) or die "$KDIR/$src: $!\n";
+  }
+  %seen = ();
+  @q = <$KDIR/*.[Sc]>;
+  @include_dirs = map { /^\// ? $_ : "$KDIR/$_" }
+    split /[\s\\]*-I/, $vars{COMMON_INCLUDE};
+  push @include_dirs, "$vars{TOP_SRCDIR}/../include/rx", "$vars{TOP_SRCDIR}/rx";
+  while (@q) {
+    $src = shift @q;
+    $content = new IO::File($src, O_RDONLY) or die "$src: $!\n";
+  LINE:
+    while (<$content>) {
+      chomp;
+      if (/^\s*#\s*include\s*[<"](?:\.\.\/)?([^\/>"]*)(.*?)[>"]/) {
+       $inc = "$1$2";
+       if (exists $seen{$inc}) {
+         next;
+       } elsif (exists $remap{$1}  &&  $2 !~ /.\//) {
+         $H = new IO::File("$KDIR/$inc", O_WRONLY|O_CREAT|O_TRUNC, 0666)
+           or die "$KDIR/$inc: $!\n";
+         print $H "#include <linux$2>\n";
+         $H->close() or die "$KDIR/$inc: $!\n";
+       } else {
+         for $dir (@include_dirs) {
+           if (-f "$dir/$inc") {
+             push @q, "$dir/$inc";
+             $seen{$inc} = 1;
+             next LINE;
+           }
+         }
+         if ($1 =~ /^(arpa|asm|.*fs|i?net|kern|ksys|linux|mach|rpc|scsi|vm)$/
+             ||  !length($2)) {
+           # Safe to ignore silently.
+         } else {
+           warn "Ignoring $_ ($inc not found)\n";
+         }
+       }
+       $seen{$inc} = 1;
+      } elsif (/^\s*#\s*include/) {
+       warn "Ignoring $_ (unrecognized syntax)\n";
+      }
+    }
   }
-  symlink("$vars{LINUX_KERNEL_PATH}/include/linux", "$KDIR/$src")
-    or die "$KDIR/$src: $!\n";
 }
 
 $cflags = "$vars{CFLAGS} $vars{COMMON_INCLUDE}";