Drop parsing of /proc/cmdline by default, instead use argc + argv[]

For most use-cases the kernel will give Finit its arguments as proper
command line args in argc + argv[], like any other program.  However,
for some users, most notably Alpine Linux, there is a slightly broken
initramfs that cannot forward more than one argument using init_args,
for such systems you can re-enable the old behavior with a configure
switch --enable-kernel-cmdline -- it's not ideal but what can you do.

The main reason for removing this feature by default is to support
use-cases where Finit runs as the init for container apps that can read
/proc -- we do not want them to use the init args from the host.

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

src/conf.c

@@ -145,24 +145,27 @@ static void parse_arg(char *arg)
 		single = 1;
 }
 
-void conf_parse_cmdline(int argc, char *argv[])
+#ifdef KERNEL_CMDLINE
+/*
+ * Parse /proc/cmdline to find args for init.  Don't use this!
+ *
+ * Instead, rely on the kernel to give Finit its arguments as
+ * regular argc + argv[].  Only use this if the system you run
+ * on has a broken initramfs system that cannot forward args
+ * to Finit properly.
+ */
+static void parse_kernel_cmdline(void)
 {
-	int dbg = 0;
-	FILE *fp;
 	char line[LINE_SIZE], *cmdline, *tok;
-
-	for (int i = 1; i < argc; i++)
-		parse_arg(argv[i]);
-
-	hide_args(argc, argv);
+	FILE *fp;
 
 	fp = fopen("/proc/cmdline", "r");
 	if (!fp)
-		goto done;
+		return;
 
 	if (!fgets(line, sizeof(line), fp)) {
 		fclose(fp);
-		goto done;
+		return;
 	}
 
 	cmdline = chomp(line);
@@ -173,8 +176,24 @@ void conf_parse_cmdline(int argc, char *argv[])
 		parse_arg(tok);
 	}
 	fclose(fp);
+}
+#else
+#define parse_kernel_cmdline()
+#endif
+
+/*
+ * Kernel gives us all non-kernel options on our cmdline
+ */
+void conf_parse_cmdline(int argc, char *argv[])
+{
+	int dbg = 0;
+
+	for (int i = 1; i < argc; i++)
+		parse_arg(argv[i]);
+
+	hide_args(argc, argv);
+	parse_kernel_cmdline();
 
-done:
 	log_init(dbg);
 }