better algorithm for finding kernel source

Reference: /n/atom/patch/applied/acidkdir
Date: Wed Feb 19 00:05:28 CET 2014
Signed-off-by: quanstro@quanstro.net

--- /sys/lib/acid/kernel	Wed Feb 19 00:05:24 2014
+++ /sys/lib/acid/kernel	Wed Feb 19 00:05:25 2014
@@ -383,9 +383,30 @@
 
 print("/sys/lib/acid/kernel");
 
+defn findkdir() {
+	local file, i, lastslash;
+
+	file = pcfile(main);
+	if file != {} then {
+		lastslash = 0;
+		i = 0;
+		while file[i] != 0 do {
+			if file[i] == '/' then lastslash=i;
+			i = i+1;
+		}
+		kdir="";
+		i = 0;
+		while i < lastslash do {
+			kdir = kdir + file[i];
+			i = i+1;
+		}
+	}
+}
+
+		
 defn needacid(s){
-	print("\trc(\"cd /sys/src/9/", kdir, "; mk ", s, ".acid\")\n");
-	print("\tinclude(\"/sys/src/9/", kdir, "/", s, ".acid\")\n");
+	print("\trc(\"cd ", kdir, "; mk ", s, ".acid\")\n");
+	print("\tinclude(\"", kdir, "/", s, ".acid\")\n");
 }
 
 defn kinit() {
@@ -395,15 +416,11 @@
 	
 	if objtype == "386" then {
 		map({"*data", KZERO, 0xffffffff, KZERO});
-		kdir="pc";
-	}
-	if (objtype == "mips" || objtype == "mips2") then {
-		kdir = "ch";
 	}
 	if objtype == "alpha" then {
 		map({"*data", KZERO, 0xffffffff, KZERO});
-		kdir = "alpha";
 	}
+	findkdir();
 	needacid("proc");
 }
 }