preinit: parse rootfstype from kernel command line

pkgs/preinit/parseopts.c

@@ -0,0 +1,97 @@
+#include <string.h>
+#include <unistd.h>
+
+static int begins_with(char * str, char * prefix)
+{
+	while(*prefix) {
+		if(*str == '\0') return 0;
+		if(*str != *prefix) return 0;
+		str++;
+		prefix++;
+	}
+	return 1;
+}
+
+
+void parseopts(char * cmdline, char **root, char **rootfstype) {
+    *root = 0;
+    *rootfstype = 0;
+
+    for(char *p = cmdline; *p; p++) {
+	if(begins_with(p, "root=")) {
+	    *root = p + strlen("root=");
+	    while(*p && (*p != ' ')) p++;
+	    
+	    if(*p) {
+		*p = '\0';
+		p++;
+	    };
+	};
+	if(begins_with(p, "rootfstype=")) {
+	    *rootfstype = p + strlen("rootfstype=");
+	    while(*p && (*p != ' ')) p++;
+	    if(*p) {
+		*p = '\0';
+		p++;
+	    };
+	};
+    };
+}
+
+#ifdef TESTS
+#include <assert.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#define die(fmt, ...) do { printf(fmt, __VA_ARGS__); exit(1); } while(0)
+#define S(x) #x
+#define expect_equal(actual, expected) \
+    if(!actual || strcmp(actual, expected)) die("%d: expected \"%s\", got \"%s\"", __LINE__, expected, actual);
+
+
+int main()
+{
+    char * root = "/dev/hda1";
+    char * rootfstype = "xiafs";
+    char *buf;
+
+    // finds root= and rootfstype= options
+    buf = strdup("liminix console=ttyS0,115200 panic=10 oops=panic init=/bin/init loglevel=8 root=/dev/ubi0_4 rootfstype=ubifs fw_devlink=off mtdparts=phram0:18M(rootfs) phram.phram=phram0,0x40400000,18874368,65536 root=/dev/mtdblock0 foo");
+    parseopts(buf, &root, &rootfstype);
+    expect_equal(root, "/dev/mtdblock0");
+    expect_equal(rootfstype, "ubifs");
+
+    // in case of duplicates, chooses the latter
+    // also: works if the option is end of string
+    buf = strdup("liminix console=ttyS0,115200 panic=10 oops=panic init=/bin/init loglevel=8 root=/dev/ubi0_4 rootfstype=ubifs fw_devlink=off mtdparts=phram0:18M(rootfs) phram.phram=phram0,0x40400000,18874368,65536 root=/dev/mtdblock0");
+    parseopts(buf, &root, &rootfstype);
+    expect_equal(root, "/dev/mtdblock0");
+    expect_equal(rootfstype, "ubifs");
+
+    // options may appear in either order
+    buf = strdup("liminix fw_devlink=off root=/dev/hda1 rootfstype=ubifs  foo");
+    parseopts(buf, &root, &rootfstype);
+    expect_equal(root, "/dev/hda1");
+    expect_equal(rootfstype, "ubifs");
+
+    buf = strdup("liminix rootfstype=ubifs fw_devlink=off root=/dev/hda1 foo");
+    parseopts(buf, &root, &rootfstype);
+    expect_equal(rootfstype, "ubifs");
+    expect_equal(root, "/dev/hda1");
+
+    // provides NULL for missing options
+    buf = strdup("liminix rufustype=ubifs fw_devlink=off foot=/dev/hda1");
+    parseopts(buf, &root, &rootfstype);
+    if(rootfstype) die("expected null rootfstype, got \"%s\"", rootfstype);
+    if(root) die("expected null root, got \"%s\"", root);
+
+    // provides empty strings for empty options
+    buf = strdup("liminix rootfstype= fw_devlink=off root= /dev/hda1");
+    parseopts(buf, &root, &rootfstype);
+    if(strlen(rootfstype)) die("expected empty rootfstype, got \"%s\"", rootfstype);
+    if(strlen(root)) die("expected null root, got \"%s\"", root);
+
+}
+
+
+#endif