kernel: add boot argument parsing

arch/x86_64/init.c

@@ -1,5 +1,6 @@
 #include <socks/pmap.h>
 #include <socks/device.h>
+#include <socks/arg.h>
 #include <socks/tty.h>
 #include <socks/kext.h>
 #include <socks/clock.h>
@@ -104,6 +105,8 @@ int ml_init(uintptr_t arg)
 {
 	multiboot_info_t *mb = (multiboot_info_t *)arg;
 
+	parse_cmdline(PTR32(mb->cmdline));
+
 	init_bootfb(mb);
 
 	bootstrap_cpu_init();

include/socks/arg.h

@@ -0,0 +1,14 @@
+#ifndef SOCKS_ARG_H_
+#define SOCKS_ARG_H_
+
+#include <stdbool.h>
+#include <socks/status.h>
+
+#define CMDLINE_MAX 4096
+
+extern kern_status_t parse_cmdline(const char *cmdline);
+
+extern const char *arg_value(const char *arg_name);
+extern bool arg_is_set(const char *arg_name);
+
+#endif

kernel/arg.c

@@ -0,0 +1,125 @@
+#include <socks/arg.h>
+#include <socks/libc/string.h>
+#include <socks/libc/ctype.h>
+
+static char g_cmdline[CMDLINE_MAX + 1] = {0};
+
+static kern_status_t remove_quotes(char *s, size_t max)
+{
+	size_t i = 0;
+	while (i < max) {
+		if (s[i] != '"') {
+			i++;
+			continue;
+		}
+
+		size_t start = i;
+		size_t end = i + 1;
+		while (s[end] != '"' && end < max) {
+			end++;
+		}
+
+		if (s[end] != '"') {
+			return KERN_INVALID_ARGUMENT;
+		}
+
+		/* length of quoted string (excluding quotes) */
+		size_t len = end - start - 1;
+
+		/* remove trailing quote */
+		s[end] = 0;
+
+		/* add 1 to len to include the null terminator */
+		memmove(s + start, s + start + 1, len + 1);
+
+		i = end + 1;
+	}
+
+	return KERN_OK;
+}
+
+kern_status_t parse_cmdline(const char *cmdline)
+{
+	strncpy(g_cmdline, cmdline, sizeof g_cmdline - 1);
+	g_cmdline[sizeof g_cmdline - 1] = 0;
+
+	bool in_string = false;
+
+	for (size_t i = 0; g_cmdline[i]; i++) {
+		char c = g_cmdline[i];
+
+		if (c == '"') {
+			in_string = !in_string;
+			continue;
+		}
+
+		if (isspace(c) && !in_string) {
+			g_cmdline[i] = 0;
+		}
+	}
+
+	if (in_string) {
+		/* unterminated string on command line */
+		return KERN_INVALID_ARGUMENT;
+	}
+
+	remove_quotes(g_cmdline, sizeof g_cmdline);
+
+	return KERN_OK;
+}
+
+static char *advance_to_next_arg(char *s, char *max)
+{
+	while (*s && s < max) {
+		s++;
+	}
+
+	while (!*s && s < max) {
+		s++;
+	}
+
+	return s;
+}
+
+
+const char *arg_value(const char *arg_name)
+{
+	char *s = g_cmdline;
+	char *end = s + sizeof g_cmdline;
+
+	while (s < end) {
+		size_t len = strlen(s);
+		size_t name_len = strcspn(s, "=");
+
+		if (!strncmp(s, arg_name, name_len)) {
+			if (len == name_len) {
+				/* arg has no value */
+				return NULL;
+			}
+
+			return s + name_len + 1;
+		}
+
+		s = advance_to_next_arg(s, end);
+	}
+
+	return NULL;
+}
+
+bool arg_is_set(const char *arg_name)
+{
+	char *s = g_cmdline;
+	char *end = s + sizeof g_cmdline;
+
+	while (s < end) {
+		size_t name_len = strcspn(s, "=");
+
+		if (!strncmp(s, arg_name, name_len)) {
+			return true;
+		}
+
+		s = advance_to_next_arg(s, end);
+	}
+
+	return false;
+}