9boot: preserve configuration on boot error, add show command

sys/man/8/9boot

@@ -19,33 +19,32 @@ gets pressed on the keyboard or the kernel file was not
 found then the loader enters the interactive
 boot console.
 
-The syntax of the boot console is the same as in
+The syntax of the boot console is the same as in the
-the
 .IR plan9.ini (8)
-file.
+file with
-.BR
+.IB key = value
-The word
+pairs setting boot parameters. In addition a few command
-.B clear
+words are recognized that are intended for interactive use:
-[
+.TP
-.I prefix
+.BI clear [prefix]
-]
+can be used to remove parameters from the configuration.
-can be used to remove parameters from the current configuration.
 If a
 .IR prefix
 is specified, the first parameter that matches the prefix
 is removed. If the
 .IR prefix
 argument is omitted, the whole configuration will be reset.
-If the word
+.TP
+.B show
+displays the current configuration in memory.
+.TP
 .B wait
-appears in the configuration then
+will return to the console prompt after processing the
-.IR 9boot
+configuration file preventing automatic boot.
-will return to the console prompt after processing the file.
+.TP
-
-The word
 .B boot
-will end the console and resume booting the kernel.
+will end the console and attempt booting the kernel.
-
+.SS
 There are many ways to boot a PC so
 .IR 9boot
 was split into a number of distinct programs one for each boot

sys/src/boot/pc/sub.c

@@ -160,6 +160,28 @@ char *confend;
 static void apmconf(int);
 static void e820conf(void);
 
+static char*
+getconf(char *s, char *buf)
+{
+	char *p, *e;
+	int n;
+
+	n = strlen(s);
+	for(p = BOOTARGS; p < confend; p = e+1){
+		for(e = p+1; e < confend; e++)
+			if(*e == '\n')
+				break;
+		if(!memcmp(p, s, n)){
+			p += n;
+			n = e - p;
+			buf[n] = 0;
+			memmove(buf, p, n);
+			return buf;
+		}
+	}
+	return 0;
+}
+
 static int
 delconf(char *s)
 {
@@ -187,18 +209,20 @@ configure(void *f, char *path)
 {
 	char line[64], *kern, *s, *p;
 	int inblock, nowait, n;
+	static int once = 1;
 
+	if(once){
+		once = 0;
 Clear:
-	kern = 0;
+		memset(BOOTLINE, 0, BOOTLINELEN);
+
+		confend = BOOTARGS;
+		memset(confend, 0, BOOTARGSLEN);
+
+		e820conf();
+	}
 	nowait = 1;
 	inblock = 0;
-
-	memset(BOOTLINE, 0, BOOTLINELEN);
-
-	confend = BOOTARGS;
-	memset(confend, 0, BOOTARGSLEN);
-
-	e820conf();
 Loop:
 	while(readline(f, line) > 0){
 		if(*line == 0 || strchr("#;=", *line))
@@ -215,6 +239,15 @@ Loop:
 			nowait=0;
 			continue;
 		}
+		if(!memcmp("show", line, 5)){
+			for(p = BOOTARGS; p < confend; p++){
+				if(*p == '\n')
+					print(crnl);
+				else
+					putc(*p);
+			}
+			continue;
+		}
 		if(!memcmp("clear", line, 5)){
 			if(line[5] == 0){
 				print("ok");
@@ -234,8 +267,6 @@ Loop:
 			apmconf('0' - line[3]);
 			continue;
 		}
-		if(!memcmp("bootfile", line, 8))
-			memmove(kern = path, p, strlen(p)+1);
 
 		s = confend;
 		memmove(confend, line, n = strlen(line)); confend += n;
@@ -248,6 +279,7 @@ Loop:
 		*confend++ = '\n';
 		*confend = 0;
 	}
+	kern = getconf("bootfile=", path);
 
 	if(f){
 		close(f);