Re: [PATCH] UUID boot on ieee1275 (Re: [PATCH] use UUIDs for cross-disk installs (Re: Issue with boot != root and chainloading))

[Robert Millan <rmh@aybabtu.com>]

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On Sun, Jul 27, 2008 at 09:28:58PM +0200, Robert Millan wrote:
> On Sun, Jul 27, 2008 at 08:37:37PM +0200, Robert Millan wrote:
> > I'm not satisfied with the current user interface of that script, but I
> > couldn't think of any better way to do it back then.  If you can improve
> > it that'd be much welcome.
> > 
> > Btw, I'm currently working on adding --prefix / uuid support to our
> > ieee1275 ports.  I'll send a patch RSN.
> 
> Here it is.  For powerpc it'd need some adjustment to start.S.  Unfortunately
> my patch appears to uncover a memory corruption problem somewhere else, which
> I haven't managed to track down yet.
> 
> But I'd still like to know if it works on other setups.

OTOH, if --prefix is used to override prefix to a value that is not of
the '(UUID=xxx)' form, it works just fine.

So I'm submitting a patch that implements --prefix, without having grub-install
use it.  This is useful already (for manual installs), and I'd like to use that
--prefix option for Coreboot later too.

-- 
Robert Millan

<GPLv2> I know my rights; I want my phone call!
<DRM> What good is a phone call… if you are unable to speak?
(as seen on /.)

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2008-07-27  Robert Millan  <rmh@aybabtu.com>

	* kern/ieee1275/init.c (grub_machine_set_prefix): If `grub_prefix'
	is non-empty, use it to set the `prefix' environment variable instead
	of the usual approach.

	* kern/i386/ieee1275/startup.S: Include `<grub/machine/kernel.h>'.
	(start): Insert a data section, with `grub_prefix' variable.

	* include/grub/powerpc/ieee1275/kernel.h [!ASM_FILE] (grub_prefix):
	New variable reference.

	* include/grub/i386/ieee1275/kernel.h (GRUB_KERNEL_MACHINE_PREFIX):
	New macro.  Defines offset of `grub_prefix' within startup.S (relative
	to `start').
	(GRUB_KERNEL_MACHINE_DATA_END): New macro.  Defines the end of data
	section within startup.S (relative to `start').

	* util/elf/grub-mkimage.c (add_segments): Receive `prefix' parameter.
	Overwrite grub_prefix with its contents, at the beginning of the
	first segment.
	(main): Understand -p|--prefix.

Index: kern/ieee1275/init.c
===================================================================
--- kern/ieee1275/init.c	(revision 1734)
+++ kern/ieee1275/init.c	(working copy)
@@ -84,6 +84,13 @@
     /* We already set prefix in grub_machine_init().  */
     return;
 
+  if (grub_prefix[0])
+    {
+      grub_env_set ("prefix", grub_prefix);
+      /* Prefix is hardcoded in kernel.elf.  */
+      return;
+    }
+
   if (grub_ieee1275_get_property (grub_ieee1275_chosen, "bootpath", &bootpath,
 				  sizeof (bootpath), 0))
     {
Index: kern/i386/ieee1275/startup.S
===================================================================
--- kern/i386/ieee1275/startup.S	(revision 1734)
+++ kern/i386/ieee1275/startup.S	(working copy)
@@ -19,6 +19,7 @@
 #define ASM_FILE	1
 
 #include <grub/symbol.h>
+#include <grub/machine/kernel.h>
 #include <grub/machine/memory.h>
 #include <grub/cpu/linux.h>
 #include <multiboot.h>
@@ -38,6 +39,24 @@
 
 start:
 _start:
+	jmp codestart
+
+	/*
+	 *  This is a special data area at a fixed offset from the beginning.
+	 */
+
+	. = EXT_C(start) + GRUB_KERNEL_MACHINE_PREFIX
+
+VARIABLE(grub_prefix)
+	/* to be filled by grub-mkimage */
+
+	/*
+	 *  Leave some breathing room for the prefix.
+	 */
+
+	. = EXT_C(start) + GRUB_KERNEL_MACHINE_DATA_END
+
+codestart:
 	movl %eax, EXT_C(grub_ieee1275_entry_fn)
 	jmp EXT_C(grub_main)
 
Index: include/grub/powerpc/ieee1275/kernel.h
===================================================================
--- include/grub/powerpc/ieee1275/kernel.h	(revision 1734)
+++ include/grub/powerpc/ieee1275/kernel.h	(working copy)
@@ -28,7 +28,15 @@
    rewrite grub-mkimage to generate valid ELF files.  */
 #define GRUB_MOD_GAP 0x8000
 
+#ifndef ASM_FILE
+
 void EXPORT_FUNC (grub_reboot) (void);
 void EXPORT_FUNC (grub_halt) (void);
 
+/* The prefix which points to the directory where GRUB modules and its
+   configuration file are located.  */
+extern char grub_prefix[];
+
+#endif
+
 #endif /* ! GRUB_KERNEL_MACHINE_HEADER */
Index: include/grub/i386/ieee1275/kernel.h
===================================================================
--- include/grub/i386/ieee1275/kernel.h	(revision 1734)
+++ include/grub/i386/ieee1275/kernel.h	(working copy)
@@ -1 +1,4 @@
 #include <grub/powerpc/ieee1275/kernel.h>
+
+#define GRUB_KERNEL_MACHINE_PREFIX	0x2
+#define GRUB_KERNEL_MACHINE_DATA_END	0x42
Index: util/elf/grub-mkimage.c
===================================================================
--- util/elf/grub-mkimage.c	(revision 1734)
+++ util/elf/grub-mkimage.c	(working copy)
@@ -158,7 +158,7 @@
 }
 
 void
-add_segments (char *dir, FILE *out, int chrp, char *mods[])
+add_segments (char *dir, char *prefix, FILE *out, int chrp, char *mods[])
 {
   Elf32_Ehdr ehdr;
   Elf32_Phdr *phdrs = NULL;
@@ -166,7 +166,7 @@
   FILE *in;
   char *kernel_path;
   grub_addr_t grub_end = 0;
-  off_t offset;
+  off_t offset, first_segment;
   int i, phdr_size;
 
   /* Read ELF header.  */
@@ -192,6 +192,8 @@
   phdrs = xmalloc (phdr_size);
   offset += ALIGN_UP (phdr_size, GRUB_TARGET_SIZEOF_LONG);
 
+  first_segment = offset;
+
   /* Copy all existing segments.  */
   for (i = 0; i < grub_target_to_host16 (ehdr.e_phnum); i++)
     {
@@ -272,6 +274,13 @@
   /* Write ELF header.  */
   grub_util_write_image_at (&ehdr, sizeof (ehdr), 0, out);
 
+  if (prefix)
+    {
+      if (GRUB_KERNEL_MACHINE_PREFIX + strlen (prefix) + 1 > GRUB_KERNEL_MACHINE_DATA_END)
+        grub_util_error ("prefix too long");
+      grub_util_write_image_at (prefix, strlen (prefix) + 1, first_segment + GRUB_KERNEL_MACHINE_PREFIX, out);
+    }
+
   free (phdrs);
   free (kernel_path);
 }
@@ -279,6 +288,7 @@
 static struct option options[] =
   {
     {"directory", required_argument, 0, 'd'},
+    {"prefix", required_argument, 0, 'p'},
     {"output", required_argument, 0, 'o'},
     {"help", no_argument, 0, 'h'},
     {"note", no_argument, 0, 'n'},
@@ -299,6 +309,7 @@
 Make a bootable image of GRUB.\n\
 \n\
 -d, --directory=DIR     use images and modules under DIR [default=%s]\n\
+-p, --prefix=DIR        set grub_prefix directory\n\
 -o, --output=FILE       output a generated image to FILE\n\
 -h, --help              display this message and exit\n\
 -n, --note              add NOTE segment for CHRP Open Firmware\n\
@@ -317,13 +328,14 @@
   FILE *fp;
   char *output = NULL;
   char *dir = NULL;
+  char *prefix = NULL;
   int chrp = 0;
 
   progname = "grub-mkimage";
 
   while (1)
     {
-      int c = getopt_long (argc, argv, "d:o:hVvn", options, 0);
+      int c = getopt_long (argc, argv, "d:p:o:hVvn", options, 0);
       if (c == -1)
 	break;
 
@@ -334,6 +346,11 @@
 	      free (dir);
 	    dir = xstrdup (optarg);
 	    break;
+	  case 'p':
+	    if (prefix)
+	      free (prefix);
+	    prefix = xstrdup (optarg);
+	    break;
 	  case 'h':
 	    usage (0);
 	    break;
@@ -364,7 +381,7 @@
   if (! fp)
     grub_util_error ("cannot open %s", output);
 
-  add_segments (dir ? : GRUB_LIBDIR, fp, chrp, argv + optind);
+  add_segments (dir ? : GRUB_LIBDIR, prefix, fp, chrp, argv + optind);
 
   fclose (fp);