9696 add /etc/system.d support
Portions contributed by: Andy Fiddaman <andy@omniosce.org>
Reviewed by: Hans Rosenfeld <hans.rosenfeld@joyent.com>
Reviewed by: Peter Tribble <peter.tribble@gmail.com>
Reviewed by: C Fraire <cfraire@me.com>
Reviewed by: Toomas Soome <tsoome@me.com>

@@ -20,11 +20,11 @@
  */
 
 /*
  * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
  * Use is subject to license terms.
- * Copyright 2016 Nexenta Systems, Inc.
+ * Copyright 2017 Nexenta Systems, Inc.
  */
 
 #include <sys/types.h>
 #include <sys/inttypes.h>
 #include <sys/param.h>

@@ -62,10 +62,11 @@
 
 static char class_file[] = CLASSFILE;
 static char dafile[] = DAFILE;
 static char dacffile[] = DACFFILE;
 
+char *self_assembly = "/etc/system.d/.self-assembly";
 char *systemfile = "/etc/system";       /* name of ascii system file */
 
 static struct sysparam *sysparam_hd;    /* head of parameters list */
 static struct sysparam *sysparam_tl;    /* tail of parameters list */
 static vmem_t *mod_sysfile_arena;       /* parser memory */

@@ -749,31 +750,25 @@
 bad:
         kobj_find_eol(file);
         return (NULL);
 }
 
-void
-mod_read_system_file(int ask)
+static void
+read_system_file(char *name)
 {
         register struct sysparam *sp;
         register struct _buf *file;
         register token_t token, last_tok;
         char tokval[MAXLINESIZE];
 
-        mod_sysfile_arena = vmem_create("mod_sysfile", NULL, 0, 8,
-            segkmem_alloc, segkmem_free, heap_arena, 0, VM_SLEEP);
-
-        if (ask)
-                mod_askparams();
-
-        if (systemfile != NULL) {
-
-                if ((file = kobj_open_file(systemfile)) ==
+        if ((file = kobj_open_file(name)) ==
                     (struct _buf *)-1) {
+                if (strcmp(name, systemfile) == 0)
                         cmn_err(CE_WARN, "cannot open system file: %s",
-                            systemfile);
+                            name);
                 } else {
+                if (sysparam_tl == NULL)
                         sysparam_tl = (struct sysparam *)&sysparam_hd;
 
                         last_tok = NEWLINE;
                         while ((token = kobj_lex(file, tokval,
                             sizeof (tokval))) != EOF) {

@@ -809,13 +804,32 @@
                                         break;
                                 }
                         }
                         kobj_close_file(file);
                 }
-        }
+}
 
+void
+mod_read_system_file(int ask)
+{
+        mod_sysfile_arena = vmem_create("mod_sysfile", NULL, 0, 8,
+            segkmem_alloc, segkmem_free, heap_arena, 0, VM_SLEEP);
+
+        if (ask)
+                mod_askparams();
+
         /*
+         * Read the user self-assembly file first
+         * to preserve existing system settings.
+         */
+        if (self_assembly != NULL)
+                read_system_file(self_assembly);
+
+        if (systemfile != NULL)
+                read_system_file(systemfile);
+
+        /*
          * Sanity check of /etc/system.
          */
         check_system_file();
 
         param_preset();