kconfig: Add error handling to KCONFIG_ALLCONFIG

- Only try to read the file specified if KCONFIG_ALL_CONFIG is set to
  something other than the empty string or "1".

- Don't use stat to check the name passed to conf_read_simple so that
  zconf_fopen can find the file in the current directory or in SRCTREE
  removing a extremely source of confusing failure, where KCONFIG_ALL_CONFIG
  was not interpreted with respect to the directory make was called in.

- If conf_read_simple fails complain clearly and stop processing.
  Allowing the simple debugging of typos.

- Clearly document the behavior so it is clear to users which
  values are treated as flags and which values are treated as
  filenames.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Michal Marek <mmarek@suse.cz>

Documentation/kbuild/kconfig.txt

@@ -53,15 +53,15 @@ KCONFIG_ALLCONFIG
 --------------------------------------------------
 (partially based on lkml email from/by Rob Landley, re: miniconfig)
 --------------------------------------------------
-The allyesconfig/allmodconfig/allnoconfig/randconfig variants can
-also use the environment variable KCONFIG_ALLCONFIG as a flag or a
-filename that contains config symbols that the user requires to be
-set to a specific value.  If KCONFIG_ALLCONFIG is used without a
-filename, "make *config" checks for a file named
-"all{yes/mod/no/def/random}.config" (corresponding to the *config command
-that was used) for symbol values that are to be forced.  If this file
-is not found, it checks for a file named "all.config" to contain forced
-values.
+The allyesconfig/allmodconfig/allnoconfig/randconfig variants can also
+use the environment variable KCONFIG_ALLCONFIG as a flag or a filename
+that contains config symbols that the user requires to be set to a
+specific value.  If KCONFIG_ALLCONFIG is used without a filename where
+KCONFIG_ALLCONFIG == "" or KCONFIG_ALLCONFIG == "1", "make *config"
+checks for a file named "all{yes/mod/no/def/random}.config"
+(corresponding to the *config command that was used) for symbol values
+that are to be forced.  If this file is not found, it checks for a
+file named "all.config" to contain forced values.
 
 This enables you to create "miniature" config (miniconfig) or custom
 config files containing just the config symbols that you are interested

scripts/kconfig/conf.c

@@ -574,8 +574,13 @@ int main(int ac, char **av)
 	case alldefconfig:
 	case randconfig:
 		name = getenv("KCONFIG_ALLCONFIG");
-		if (name && !stat(name, &tmpstat)) {
-			conf_read_simple(name, S_DEF_USER);
+		if (name && (strcmp(name, "") != 0) && (strcmp(name, "1") != 0)) {
+			if (conf_read_simple(name, S_DEF_USER)) {
+				fprintf(stderr,
+					_("*** Can't read seed configuration \"%s\"!\n"),
+					name);
+				exit(1);
+			}
 			break;
 		}
 		switch (input_mode) {
@@ -586,10 +591,13 @@ int main(int ac, char **av)
 		case randconfig:	name = "allrandom.config"; break;
 		default: break;
 		}
-		if (!stat(name, &tmpstat))
-			conf_read_simple(name, S_DEF_USER);
-		else if (!stat("all.config", &tmpstat))
-			conf_read_simple("all.config", S_DEF_USER);
+		if (conf_read_simple(name, S_DEF_USER) &&
+		    conf_read_simple("all.config", S_DEF_USER)) {
+			fprintf(stderr,
+				_("*** KCONFIG_ALLCONFIG set, but no \"%s\" or \"all.config\" file found\n"),
+				name);
+			exit(1);
+		}
 		break;
 	default:
 		break;