8 files changed, 75 insertions(+), 7 deletions(-)

M system-v2/nix-sys/.gitignore.do
A system-v2/nix-sys/chattr/disable.c
A system-v2/nix-sys/chattr/enable.c
A system-v2/nix-sys/default.h.do
M system-v2/nix-sys/default.nix
M system-v2/nix-sys/default.o.do
M system-v2/nix-sys/main.c
M system-v2/nix-sys/nix-sys.do

@@ 5,6 5,8 @@ redo-targets | sed 's/..//' > $3
 cat << EOF >> $3
 .gitignore
 .dep.*
+.depend.*
+.target.*
 .lock.*
 index.cdb
 config.h

@@ 0,0 1,2 @@
+int immutable_on(const char *_path) { return 0; }
+int immutable_off(const char *_path) { return 0; }

@@ 0,0 1,35 @@
+#include <linux/fs.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/ioctl.h>
+#include <unistd.h>
+#include <fcntl.h>
+
+static int fssetflags(int fd, unsigned int flags)
+{
+	return ioctl(fd, FS_IOC_SETFLAGS, (void*)&flags);
+}
+
+static int path_setattrs(const char *path, unsigned int flags)
+{
+	int fd;
+	int err;
+
+	fd = open(path, O_NONBLOCK|O_RDONLY);
+	if (fd < 0)
+		return 1;
+	err = fssetflags(fd, flags);
+	close(fd);
+
+	return err;
+}
+
+int immutable_on(const char *path)
+{
+	return path_setattrs(path, FS_IMMUTABLE_FL);
+}
+
+int immutable_off(const char *path)
+{
+	return path_setattrs(path, 0);
+}

@@ 0,0 1,7 @@
+#!/bin/sh -eu
+feature=$(cat conf/feature-$2)
+src="$2/$feature.c"
+
+redo-ifchange $src conf/feature-$2
+
+cproto -qe < $src > $3

@@ 1,12 1,13 @@
-{ stdenv, tinycdb, nix-sys-generate, redo-c, manifest ? {} }:
+{ stdenv, tinycdb, nix-sys-generate, manifest ? { }, redo-c, cproto
+, linuxHeaders ? null }:
 assert manifest != null;
 let
 in stdenv.mkDerivation {
   name = "nix-sys";
   src = ./.;
   outputs = [ "out" "cdb" ];
-  nativeBuildInputs = [ nix-sys-generate redo-c ];
-  buildInputs = [ tinycdb ];
+  nativeBuildInputs = [ nix-sys-generate redo-c cproto ];
+  buildInputs = [ tinycdb linuxHeaders ];
   configurePhase = ''
     mkdir conf
     echo $out > conf/out


@@ 14,6 15,8 @@ in stdenv.mkDerivation {
     echo "$manifest" > conf/manifest
     echo "${stdenv.cc.targetPrefix}cc -static -O2" > conf/cc
     echo "${stdenv.cc.targetPrefix}cc" > conf/ld
+    echo "${if linuxHeaders != null then "enable" else "disable"}" \
+      > conf/feature-chattr
   '';
   buildPhase = "redo";
   installPhase = ''


@@ 24,4 27,3 @@ in stdenv.mkDerivation {
   postFixup = "rm -fr $out/nix-support";
   manifest = builtins.toJSON manifest;
 }
-

@@ 1,4 1,13 @@
 #!/bin/sh -eu
 cc=$(cat conf/cc)
-redo-ifchange conf/cc generate $2.c
-$cc $2.c -c -o $3
+redo-ifchange conf/cc generate chattr.h
+
+if [ -e "$2.c" ] ; then
+	src="$2.c"
+else
+	redo-ifchange "conf/feature-$2"
+	src="$2/$(cat conf/feature-$2).c"
+fi
+
+redo-ifchange "$src"
+$cc "$src" -c -o $3

@@ 8,6 8,8 @@
 #include <unistd.h>
 #include <stdio.h>
 
+#include "chattr.h"
+
 struct copy_a {
 	const char *source;
 	const char *tmp;


@@ 263,7 265,16 @@ int main(int argc, char **argv)
 		write2("renaming copy into ");
 		write2_s(obj->destination);
 		write2("... ");
+
+		/* Make file immutable (chattr +i) so it can't be
+		 * modified by mistake. Linux-only.
+		 *
+		 * TODO: Check errors properly.
+		 */
+		(void) immutable_off(obj->destination);
 		err = rename(obj->tmp, obj->destination);
+		(void) immutable_on(obj->destination);
+
 		if (err) {
 			write2("fail\n");
 			return 1;

@@ 1,5 1,5 @@
 #!/bin/sh -eu
 ld=$(cat conf/ld)
-objs="main.o"
+objs="main.o chattr.o"
 redo-ifchange conf/ld $objs
 $ld $objs -lcdb -o $3