[PATCH] Xen Grub-style boot loader

[PATCH] Xen Grub-style boot loader

[Anthony Liguori]

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Ok, here's something I hacked up this afternoon to try and get the ball 
moving on this.

It's a simple grub style ncurses application.  This is my ncurses app so 
it's probably even easier than what I did.  It parses a grub.conf file 
and let's a user pick an entry.

Right now it just prints out what the user selected.  I'm not sure how 
it should integrate into the existing tools.  Thoughts?  Integrating it 
shouldn't be pretty easy.

Note: It looks quite ugly in gnome-terminal.  I'm sure there's a way to 
handle the different term types better in curses.  It looks just fine 
though on a real terminal though.

Regards,

Anthony Liguori
Email: aliguori@us.ibm.com

Signed-off-by: Anthony Liguori

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diff -urN xenoloader-empty/Makefile xenoloader/Makefile
--- xenoloader-empty/Makefile	1969-12-31 18:00:00.000000000 -0600
+++ xenoloader/Makefile	2005-02-03 14:47:08.000000000 -0600
@@ -0,0 +1,31 @@
+###############################################################################
+##
+##   Makefile
+##
+##   Copyright (C) International Business Machines  Corp., 2005
+##   Author(s): Anthony Liguori (aliguori@us.ibm.com)
+##
+##   Xen Psuedo-Boot Loader
+##
+##   This library is free software; you can redistribute it and/or modify
+##   it under the terms of the GNU Lesser General Public License as published
+##   by the Free Software Foundation; either version 2.1 of the License, or
+##   (at your option) any later version.
+##
+##   This library is distributed in the hope that it will be useful,
+##   but WITHOUT ANY WARRANTY; without even the implied warranty of
+##   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See
+##   the GNU Lesser General Public License for more details.
+##
+##   You should have received a copy of the GNU Lesser General Public License
+##   along with this library; if not, write to the Free Software
+##   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+##
+###############################################################################
+
+CFLAGS=-Wall -g
+
+all: main.o
+	$(CC) $(CFLAGS) -o xenoloader main.o -lcurses
+
+clean:; $(RM) main.o xenoloader
diff -urN xenoloader-empty/main.c xenoloader/main.c
--- xenoloader-empty/main.c	1969-12-31 18:00:00.000000000 -0600
+++ xenoloader/main.c	2005-02-03 14:56:00.000000000 -0600
@@ -0,0 +1,278 @@
+/*\
+ *   xenoloader/main.c
+ *
+ *   Copyright (C) International Business Machines  Corp., 2005
+ *   Author(s): Anthony Liguori (aliguori@us.ibm.com)
+ *
+ *   Xen Psuedo-Boot Loader
+ *
+ *   This library is free software; you can redistribute it and/or modify
+ *   it under the terms of the GNU Lesser General Public License as published
+ *   by the Free Software Foundation; either version 2.1 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This library is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See
+ *   the GNU Lesser General Public License for more details.
+ *
+ *   You should have received a copy of the GNU Lesser General Public License
+ *   along with this library; if not, write to the Free Software
+ *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+\*/
+
+#include <curses.h>
+#include <signal.h>
+#include <stdlib.h>
+#include <ctype.h>
+#include <string.h>
+#include <malloc.h>
+
+/* simple structure representing a single grub
+   command.  argv[0] is the name of the command.
+   Use CMD_REST to concatinate multiple arguments
+   while preserving original spacing */
+struct grub_cmd {
+  int argc;
+  char **argv;
+  char *line;
+};
+
+/* the x,y offset of the first entry to select */
+#define X_OFFSET 3
+#define Y_OFFSET 6
+
+/* gets the concatination of the rest of the line
+   starting at argv[i] */
+#define CMD_REST(cmd, i) ((cmd).line + ((cmd).argv[(i)] - (cmd).argv[0]))
+
+/* reads a grub configuration file and returns a null-terminated array of
+   grub commands */
+struct grub_cmd *read_grub_conf(const char *file)
+{
+  FILE *f = fopen(file, "r");
+  char buffer[4096];
+  struct grub_cmd *cmds = 0;
+  size_t capacity = 0;
+  size_t size = 0;
+
+  if (!f) return NULL;
+
+  while(fgets(buffer, sizeof(buffer), f)) {
+    char *ptr = buffer;
+    int words = 0;
+    int in_word = 0;
+
+    /* skip spaces */
+    while (isspace(*ptr)) ptr++;
+
+    /* skip comments and blank lines */
+    if (*ptr == '#' || !*ptr) continue;
+
+    /* make sure we have enough room for this command and the null terminator */
+    if ((size + 2) > capacity) {
+      capacity += 100;
+      cmds = realloc(cmds, capacity * sizeof(cmds[0]));
+    }
+
+    cmds[size].line = strdup(ptr);
+
+    /* count number of words */
+    for (ptr = cmds[size].line; *ptr; ptr++) {
+      if (isspace(*ptr)) {
+	in_word = 0;
+      } else if (!in_word) {
+	words++;
+	in_word = 1;
+      }
+      if (*ptr == '\r' || *ptr == '\n') *ptr = 0;
+    }
+
+    /* allocate argc/argv */
+    cmds[size].argc = words;
+    cmds[size].argv = malloc(sizeof(char*) * words);
+
+    /* duplicate a string to tokenize */
+    cmds[size].argv[0] = strdup(cmds[size].line);
+    words = 1;
+    in_word = 1;
+
+    /* tokenize */
+    for (ptr = cmds[size].argv[0]; *ptr; ptr++) {
+      if (isspace(*ptr)) {
+	if (in_word) *ptr = 0;
+	in_word = 0;
+      } else if (!in_word) {
+	cmds[size].argv[words] = ptr;
+	words++;
+	in_word = 1;
+      }
+    }
+
+    size++;
+  }
+
+  fclose(f);
+
+  /* NULL terminate */
+  cmds[size].argc = 0;
+  cmds[size].argv = 0;
+  cmds[size].line = 0;
+
+  return cmds;
+}
+
+/* quick routine that draws a box using ASCII art.  There's
+   probably a better way to do this with curses */
+static void make_box(int x, int y, int width, int height)
+{
+  int i;
+
+  mvaddch(y, x, 0xda);
+  for (i = x + 1; i < x + width; i++) {
+    mvaddch(y, i, 0xc4);
+  }
+  mvaddch(y, x+width, 0xbf);
+
+  for (i = y + 1; i < y + height; i++) {
+    mvaddch(i, x, 0xb3);
+    mvaddch(i, x+width, 0xb3);
+  }
+
+  mvaddch(y+height, x, 0xc0);
+  for (i = x + 1; i < x + width; i++) {
+    mvaddch(y+height, i, 0xc4);
+  }
+  mvaddch(y+height, x+width, 0xd9);
+}
+
+/* signal handler */
+static void finish(int sig)
+{
+  endwin();
+  exit(0);
+}
+
+int main(int argc, char **argv)
+{
+  int ch;
+  int pos = 0;
+  struct grub_cmd *cmds;
+  int selected = -1;
+  int i;
+  int n = 0;
+
+  if (argc != 2) {
+    printf("Usage: %s CONFIG\n", argv[0]);
+    exit(1);
+  }
+
+  /* Read the grub file */
+  cmds = read_grub_conf(argv[1]);
+  if (!cmds) {
+    fprintf(stderr, "Error reading `%s': %m\n", argv[1]);
+    exit(1);
+  }
+
+  /* Set up curses and signal handlers */
+  signal(SIGINT, finish);
+  initscr();
+  keypad(stdscr, TRUE);
+  intrflush(stdscr, FALSE);
+  nonl();
+  cbreak();
+  noecho();
+
+  /* Display banner */
+  mvaddstr(2, 2, "XenoLoader v0.0.1");
+
+  /* Display box with choices */
+  make_box(1, Y_OFFSET - 2, 74, 10);
+  for (i = 0; cmds[i].line; i++) {
+    if (!strcmp(cmds[i].argv[0], "title")) {
+      mvaddstr(Y_OFFSET + n, X_OFFSET + 2, CMD_REST(cmds[i], 1));
+      n++;
+    }
+  }
+
+  /* Display usage text */
+  mvaddstr(18, 2, "Use the up and down keys to select which entry is highlighted.");
+  mvaddstr(19, 2, "Press enter to boot the selected OS.");
+
+  /* Select the first choice */
+  mvaddstr(Y_OFFSET + pos, X_OFFSET, " ");
+
+  /* Input loop */
+  while (selected == -1 && (ch = getch()) != EOF) {
+    int new_pos = pos;
+    switch (ch) {
+    case KEY_UP:
+      new_pos--;
+      break;
+    case KEY_DOWN:
+      new_pos++;
+      break;
+    case '\n':
+    case '\r':
+      selected = pos;
+      break;
+    }
+    
+    new_pos += n;
+    new_pos %= n;
+    
+    if (new_pos != pos) {
+      mvaddstr(Y_OFFSET + new_pos, X_OFFSET, " ");
+      pos = new_pos;
+    }
+  }
+
+  /* Close the curses session */
+  endwin();
+
+  /* This is all horribly inefficient but quick to write */
+
+  /* Find the index of the selected title */
+  n = 0;
+  for (i = 0; cmds[i].line; i++) {
+    if (!strcmp(cmds[i].argv[0], "title")) {
+      if (n == selected) {
+	break;
+      }
+      n++;
+    }
+  }
+
+  if (!cmds[i].line) {
+    printf("No kernel selected\n");
+  } else {
+    const char *title = CMD_REST(cmds[i], 1);
+    const char *kernel = "";
+    const char *cli = "";
+    const char *root = "";
+
+    /* Read the options after the selected title until
+       the next title looking for the ones we care about
+    */
+    for (i++; cmds[i].line; i++) {
+      if (!strcmp(cmds[i].argv[0], "title")) {
+	break;
+      } else if (!strcmp(cmds[i].argv[0], "kernel")) {
+	kernel = cmds[i].argv[1];
+	if (cmds[i].argc > 2) {
+	  cli = CMD_REST(cmds[i], 2);
+	}
+      } else if (!strcmp(cmds[i].argv[0], "root")) {
+	root = CMD_REST(cmds[i], 1);
+      }
+    }
+
+    /* We've got our info.. now what do we do with it */
+    printf("Selected kernel `%s'\n", title);
+    printf("Root is `%s'\n", root);
+    printf("Kernel image is `%s'\n", kernel);
+    printf("Kernel command line is `%s'\n", cli);
+  }
+
+  return 0;
+}

RE: [PATCH] Xen Grub-style boot loader

[Ian Pratt]

> It's a simple grub style ncurses application.  This is my 
> ncurses app so 
> it's probably even easier than what I did.  It parses a 
> grub.conf file 
> and let's a user pick an entry.

I think to be useful this would need to run within the guest domain such that the grub menu appeared over the guest console connection. We'd have to use something akin to a real bootloader (but 32bit) to pull in the image and jump at it. Using linux with a suitable initrd and kexec might be a good soloution.

I'm not sure that the interactive selection of kernels is the #1 requirement here -- I think its more about being able to read the kernel from the domain's file system, and to be able to control the command line options. 

Ian


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Re: RE: [PATCH] Xen Grub-style boot loader

[Jacob Gorm Hansen]

Ian Pratt wrote:
>>It's a simple grub style ncurses application.  This is my 
>>ncurses app so 
>>it's probably even easier than what I did.  It parses a 
>>grub.conf file 
>>and let's a user pick an entry.
> 
> 
> I think to be useful this would need to run within the guest domain such that the grub menu appeared over the guest console connection. We'd have to use something akin to a real bootloader (but 32bit) to pull in the image and jump at it. Using linux with a suitable initrd and kexec might be a good soloution.
> 
> I'm not sure that the interactive selection of kernels is the #1 requirement here -- I think its more about being able to read the kernel from the domain's file system, and to be able to control the command line options. 

I have some code for pulling in a Linux ELF image via UIP-TCP under 
Xen1.3, unpacking it and jumping at it, if anyone is interested. The 
total bootloader binary is 30kb.

The networking driver needs to be ported to Xen 2.0, but otherwise it 
should just work.

Jacob


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Re: [PATCH] Xen Grub-style boot loader

[Anthony Liguori]

Ian Pratt wrote:

>I think to be useful this would need to run within the guest domain such that the grub menu appeared over the guest console connection. We'd have to use something akin to a real bootloader (but 32bit) to pull in the image and jump at it. Using linux with a suitable initrd and kexec might be a good soloution.
>  
>
Making the console appear over the guest connection isn't hard while 
still having the boot loader be a dom0 process.  It's particularly easy 
if you make the console visible as a tty.  In the current Xend 
architecture, you would just dup the socket as the std(in|out) of the 
process and exec the boot loader before starting the domain.

I think the only real advantage to having it be a part of domain-U is 
that you avoid the problem with mounting a file system.  The more I 
think about it though the more of a security concerns worry me.  Long 
term, I think a domU loader is a better solution.  However, I think 
there's a large class of users where a dom0 boot loader would be just fine.

>I'm not sure that the interactive selection of kernels is the #1 requirement here -- I think its more about being able to read the kernel from the domain's file system, and to be able to control the command line options. 
>  
>
It's definitely not the #1 requirement but it's certainly useful.  You 
don't really need a boot loader to read the kernel from the domain's 
file system or to give the user the ability to control the command line.

Would you being willing to accept a boot loader that ran as a dom0 
process and exported it's screen through the console?  Even if it was 
only a temporary solution until a better boot loader was written?  I ask 
because I can probably code up the rest (I already can read the 
grub.conf off of a specified device) by tonight or tomorrow.

I think it would take more time than I could invest to do the dom0 
approach any time soon.  Unless of course someone else is willing to do 
it in which case I agree that the dom0 approach is superior :-)

Regards,
Anthony Liguori

>Ian
>
>  
>



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Re: [PATCH] Xen Grub-style boot loader

[Anthony Liguori]

Anthony Liguori wrote:

> It's a simple grub style ncurses application.  This is my ncurses app 
> so it's probably even easier than what I did.  It parses a grub.conf 
> file and let's a user pick an entry.
>
> Right now it just prints out what the user selected.  I'm not sure how 
> it should integrate into the existing tools.  Thoughts?  Integrating 
> it shouldn't be pretty easy.

I'm sorry, my typing seems a bit off today.  It should read, "This is my 
first ncurses app" and "Integrating it should be pretty easy".  I didn't 
want anyone to think that it would be difficult to integrate :-)

Regards,
Anthony Liguori


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Re: Re: [PATCH] Xen Grub-style boot loader

[Jeremy Katz]

On Thu, 2005-02-03 at 17:37 -0600, Anthony Liguori wrote:
> Would you being willing to accept a boot loader that ran as a dom0 
> process and exported it's screen through the console?  Even if it was 
> only a temporary solution until a better boot loader was written?  I ask 
> because I can probably code up the rest (I already can read the 
> grub.conf off of a specified device) by tonight or tomorrow.

I at least think that this would be an interesting point to start from.
And quite possibly interesting in a longer term.

Jeremy



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