[U-Boot-Users] [RFC] Implementing Boot Image Fallback on U-Boot

[Makito SHIOKAWA <mshiokawa@miraclelinux.com>]

Hi,

Thank you for your reply.

> Are you aware that U-Boot has scripting capabilities, to the extend of
> being able to run shell scripts?

What I was thinking as "boomf" is like a patch bellow (It is for U-Boot 1.1.4 
and just a prototype). I knew about scripting, but I thought it was difficult 
to do this processing by a script (especially error checks). Also, I didn't 
think it's a good way to set corresponding long script to "bootcmd" (U-Boot 
environment area is limited).

But, is it better to do this processing by a script? (Or, is there more proper 
way to do same kind of things?)

> What you are asking for can be pretty easily implemented using a few
> macro definitions utilizing the aforementioned features.

Is it able to do without using all of the elements (new command, new 
environment variable, fw_setenv) I wrote in the first mail?
I'll check documents and sources over again, but I would appreciate if you can 
give me some keywords of those features ...


Best regards,

---
  common/Makefile     |    2
  common/cmd_bootmf.c |  256 +++++++++++++++++++++++++++++++++++++++++++++++++++
  2 files changed, 257 insertions(+), 1 deletion(-)

--- a/common/Makefile
+++ b/common/Makefile
@@ -29,7 +29,7 @@ AOBJS	=

  COBJS	= main.o ACEX1K.o altera.o bedbug.o circbuf.o \
  	  cmd_ace.o cmd_autoscript.o \
-	  cmd_bdinfo.o cmd_bedbug.o cmd_bmp.o cmd_boot.o cmd_bootm.o \
+	  cmd_bdinfo.o cmd_bedbug.o cmd_bmp.o cmd_boot.o cmd_bootm.o cmd_bootmf.o \
  	  cmd_cache.o cmd_console.o \
  	  cmd_date.o cmd_dcr.o cmd_diag.o cmd_display.o cmd_doc.o cmd_dtt.o \
  	  cmd_eeprom.o cmd_elf.o cmd_ext2.o \
--- /dev/null
+++ b/common/cmd_bootmf.c
@@ -0,0 +1,256 @@
+/*
+ * (C) Copyright 2008
+ * Makito SHIOKAWA, MIRACLE LINUX CORPORATION, mshiokawa at miraclelinux.com
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
+ * MA 02111-1307 USA
+ */
+
+#include <common.h>
+#include <command.h>
+
+extern int do_bootm (cmd_tbl_t *, int, int, char *[]);
+
+/*
+ * Codes are taken from GRUB
+ */
+
+#define MAXINT 0x7FFFFFFF
+#define MAX_FALLBACK_ENTRIES 8
+
+static int default_entry;
+static int fallback_entryno;
+static int fallback_entries[MAX_FALLBACK_ENTRIES];
+static int current_entryno;
+
+static int tolower (int c)
+{
+	if (c >= 'A' && c <= 'Z')
+		return (c + ('a' - 'A'));
+	
+	return c;
+}
+
+static int safe_parse_maxint (char **str_ptr, int *myint_ptr)
+{
+	char *ptr = *str_ptr;
+	int myint = 0;
+	int mult = 10, found = 0;
+
+	/*
+	 *  Is this a hex number?
+	 */
+	if (*ptr == '0' && tolower (*(ptr + 1)) == 'x')
+	{
+		ptr += 2;
+		mult = 16;
+	}
+	
+	while (1)
+	{
+		/* A bit tricky. This below makes use of the equivalence:
+		   (A >= B && A <= C) <=> ((A - B) <= (C - B))
+		   when C > B and A is unsigned.  */
+		unsigned int digit;
+		
+		digit = tolower (*ptr) - '0';
+		if (digit > 9)
+		{
+			digit -= 'a' - '0';
+			if (mult == 10 || digit > 5)
+				break;
+			digit += 10;
+		}
+		
+		found = 1;
+		if (myint > ((MAXINT - digit) / mult))
+		{
+			return 0;
+		}
+		myint = (myint * mult) + digit;
+		ptr++;
+	}
+	
+	if (!found)
+	{
+		return 0;
+	}
+	
+	*str_ptr = ptr;
+	*myint_ptr = myint;
+	
+	return 1;
+}
+
+static int default_func (char *arg)
+{
+	if (! safe_parse_maxint (&arg, &default_entry))
+		return 1;
+
+	return 0;
+}
+
+/* Find the next word from CMDLINE and return the pointer. If
+   AFTER_EQUAL is non-zero, assume that the character `=' is treated as
+   a space. Caution: this assumption is for backward compatibility.  */
+static char *skip_to (int after_equal, char *cmdline)
+{
+	/* Skip until we hit whitespace, or maybe an equal sign. */
+	while (*cmdline && *cmdline != ' ' && *cmdline != '\t' &&
+	      ! (after_equal && *cmdline == '='))
+		cmdline ++;
+	
+	/* Skip whitespace, and maybe equal signs. */
+	while (*cmdline == ' ' || *cmdline == '\t' ||
+	      (after_equal && *cmdline == '='))
+		cmdline ++;
+
+	return cmdline;
+}
+
+static int fallback_func (char *arg)
+{
+	int i = 0;
+	
+	while (*arg)
+	{
+		int entry;
+		int j;
+		
+		if (! safe_parse_maxint (&arg, &entry))
+			return 1;
+		
+		/* Remove duplications to prevent infinite looping.  */
+		for (j = 0; j < i; j++)
+			if (entry == fallback_entries[j])
+				break;
+		if (j != i)
+			continue;
+		
+		fallback_entries[i++] = entry;
+		if (i == MAX_FALLBACK_ENTRIES)
+			break;
+		
+		arg = skip_to (0, arg);
+	}
+	
+	if (i < MAX_FALLBACK_ENTRIES)
+		fallback_entries[i] = -1;
+	
+	fallback_entryno = (i == 0) ? -1 : 0;
+	
+	return 0;
+}
+
+static int savedefault_func (void)
+{
+	int entryno;
+	int i;
+	int index = 0;
+	char buf[16];
+	
+	for (i = 0; i < MAX_FALLBACK_ENTRIES; i++)
+	{
+		if (fallback_entries[i] < 0)
+			break;
+		if (fallback_entries[i] == current_entryno)
+		{
+			index = i + 1;
+			break;
+		}
+	}
+	
+	if (index >= MAX_FALLBACK_ENTRIES || fallback_entries[index] < 0)
+	{
+		/* This is the last.  */
+		return 1;
+	}
+	
+	entryno = fallback_entries[index];
+	
+	sprintf(buf, "%d", entryno);
+	setenv("default", buf);
+	saveenv();
+	
+	return 0;
+}
+
+/*
+ * TODO: Add error check
+ */
+
+int do_bootmf (cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
+{
+	char *s;
+	
+	default_entry = 0;
+	fallback_entryno = -1;
+	fallback_entries[0] = -1;
+	current_entryno = 0;
+	
+	if ((s = getenv("default")) != NULL)
+		default_func(s);
+	
+	if ((s = getenv("fallback")) != NULL)
+		fallback_func(s);
+	
+	while (1) {
+		char buf[16];
+		char *local_args[2];
+		ulong addr;
+		int rcode = 0;
+		
+		if (!current_entryno)
+			current_entryno = default_entry;
+		
+		savedefault_func();
+		
+		sprintf(buf, "imgaddr%d", current_entryno);
+		if ((s = getenv(buf)) != NULL)
+			addr = simple_strtoul(s, NULL, 16);
+		else
+			break;
+		
+		sprintf(buf, "bootargs%d", current_entryno);
+		if ((s = getenv(buf)) != NULL)
+			setenv("bootargs", s);
+		else
+			break;
+		
+		load_addr = addr;
+		local_args[0] = argv[0];
+		local_args[1] = NULL;
+		rcode = do_bootm (cmdtp, 0, 1, local_args);
+		if (rcode) {
+			if (fallback_entryno >= 0) {
+				current_entryno = fallback_entries[fallback_entryno];
+				fallback_entryno++;
+				if (fallback_entryno >= MAX_FALLBACK_ENTRIES
+				   || fallback_entries[fallback_entryno] < 0)
+					fallback_entryno = -1;
+			} else
+				break;
+		} else
+			break;
+	}
+	
+	return 1;
+}
+
+U_BOOT_CMD(
+	bootmf, 1, 1, do_bootmf,
+	"bootmf - boot application image from memory with fallback enabled\n",
+	NULL
+);

-- 
MIRACLE LINUX CORPORATION
Makito SHIOKAWA