[PATCH][TAKE 3] THE LINUX/I386 BOOT PROTOCOL - Breaking the 256 limit

[Alon Bar-Lev <alon.barlev@gmail.com>]

Extending the kernel parameters to a user determined size
on boot protocol >=2.02 for i386 and x86_64 architectures.

Signed-off-by: Alon Bar-Lev <alon.barlev@gmail.com>

---

Hello,

Current implementation allows the kernel to receive up to 
255 characters from the bootloader.

In current environment, the command-line is used in order to 
specify many values, including suspend/resume, module 
arguments, splash, initramfs and more.

255 characters are not enough anymore.

This is take 3 of this submission:

Take 1 - Patch that allows command-line size to be 
determined in menuconfig. People did not want to see a new 
config option.

Take 2 - Removed the menuconfig into a fixed 2048 size. This 
patch was rejected. This is what the 2.6.11-rc2 changelog 
has to say about the matter:

> Revert "x86_64/i386: increase command line size" patch
> It's a bootup dependancy, you can't just increase it
> randomly, and it breaks booting with LILO.
> Pointed out by Janos Farkas and Adrian Bunk.

Take 3 (current) - Back to menuconfig option, so it won't 
break LILO (Although if it is broken because of this, it 
should be fixed...).

Please consider to merge.

If any of you think that this should be applied for other
architectures, please reply.

Current architectures that have 256 limit are:
alpha, cris, i386, m64k, mips, sh, sh64, sparc, sparc64,
x86_64, xtensa

Current architectures that have 512 values are:
frv(512), h8300(512), ia64(512), m32r(512), m68knommu(512),
mips(512), powerpc(512), v850(512)

Current architectures that are OK:
arm(1024), arm26(1024), parisc(1024)

Current strange ones:
s390(896) - I guess IBM has a good reason for this constant...

Best Regards,
Alon Bar-Lev

diff -urNp linux-2.6.16/arch/i386/Kconfig linux-2.6.16.new/arch/i386/Kconfig
--- linux-2.6.16/arch/i386/Kconfig	2006-03-20 07:53:29.000000000 +0200
+++ linux-2.6.16.new/arch/i386/Kconfig	2006-04-14 01:35:06.000000000 +0300
@@ -644,6 +644,14 @@ config EFI
 	anything about EFI).  However, even with this option, the resultant
 	kernel should continue to boot on existing non-EFI platforms.
 
+config COMMAND_LINE_SIZE
+	int "Maximum kernel command-line size"
+	range 256 4096
+	default 256
+	---help---
+	This enables adjusting maximum command-line size. If you are unsure
+	specify 256.
+
 config IRQBALANCE
  	bool "Enable kernel irq balancing"
 	depends on SMP && X86_IO_APIC
diff -urNp linux-2.6.16/arch/x86_64/Kconfig linux-2.6.16.new/arch/x86_64/Kconfig
--- linux-2.6.16/arch/x86_64/Kconfig	2006-03-20 07:53:29.000000000 +0200
+++ linux-2.6.16.new/arch/x86_64/Kconfig	2006-04-14 01:35:30.000000000 +0300
@@ -445,6 +445,14 @@ config PHYSICAL_START
 
 	  Don't change this unless you know what you are doing.
 
+config COMMAND_LINE_SIZE
+	int "Maximum kernel command-line size"
+	range 256 4096
+	default 256
+	---help---
+	This enables adjusting maximum command-line size. If you are unsure
+	specify 256.
+
 config SECCOMP
 	bool "Enable seccomp to safely compute untrusted bytecode"
 	depends on PROC_FS
diff -urNp linux-2.6.16/Documentation/i386/boot.txt linux-2.6.16.new/Documentation/i386/boot.txt
--- linux-2.6.16/Documentation/i386/boot.txt	2006-03-20 07:53:29.000000000 +0200
+++ linux-2.6.16.new/Documentation/i386/boot.txt	2006-04-14 01:55:47.000000000 +0300
@@ -235,11 +235,8 @@ loader to communicate with the kernel.  
 relevant to the boot loader itself, see "special command line options"
 below.
 
-The kernel command line is a null-terminated string currently up to
-255 characters long, plus the final null.  A string that is too long
-will be automatically truncated by the kernel, a boot loader may allow
-a longer command line to be passed to permit future kernels to extend
-this limit.
+The kernel command line is a null-terminated string. A string that is too
+long will be automatically truncated by the kernel.
 
 If the boot protocol version is 2.02 or later, the address of the
 kernel command line is given by the header field cmd_line_ptr (see
@@ -260,6 +257,9 @@ command line is entered using the follow
 	covered by setup_move_size, so you may need to adjust this
 	field.
 
+       The kernel command line *must* be 256 bytes including the
+       final null.
+
 
 **** SAMPLE BOOT CONFIGURATION
 
diff -urNp linux-2.6.16/include/asm-i386/param.h linux-2.6.16.new/include/asm-i386/param.h
--- linux-2.6.16/include/asm-i386/param.h	2006-03-20 07:53:29.000000000 +0200
+++ linux-2.6.16.new/include/asm-i386/param.h	2006-04-14 02:00:45.000000000 +0300
@@ -19,6 +19,15 @@
 #endif
 
 #define MAXHOSTNAMELEN	64	/* max length of hostname */
+
+/*
+ * This COMMAND_LINE_SIZE definition was left here
+ * for compatability, its correct location is in setup.h.
+ * Boot loaders that use this parameters will continue
+ * to use 256 maximum command-line size.
+ */
+#ifndef CONFIG_COMMAND_LINE_SIZE
 #define COMMAND_LINE_SIZE 256
+#endif
 
 #endif
diff -urNp linux-2.6.16/include/asm-i386/setup.h linux-2.6.16.new/include/asm-i386/setup.h
--- linux-2.6.16/include/asm-i386/setup.h	2006-03-20 07:53:29.000000000 +0200
+++ linux-2.6.16.new/include/asm-i386/setup.h	2006-04-14 01:32:16.000000000 +0300
@@ -17,7 +17,7 @@
 #define MAX_NONPAE_PFN	(1 << 20)
 
 #define PARAM_SIZE 4096
-#define COMMAND_LINE_SIZE 256
+#define COMMAND_LINE_SIZE CONFIG_COMMAND_LINE_SIZE
 
 #define OLD_CL_MAGIC_ADDR	0x90020
 #define OLD_CL_MAGIC		0xA33F
diff -urNp linux-2.6.16/include/asm-x86_64/setup.h linux-2.6.16.new/include/asm-x86_64/setup.h
--- linux-2.6.16/include/asm-x86_64/setup.h	2006-03-20 07:53:29.000000000 +0200
+++ linux-2.6.16.new/include/asm-x86_64/setup.h	2006-04-14 01:33:27.000000000 +0300
@@ -1,6 +1,6 @@
 #ifndef _x8664_SETUP_H
 #define _x8664_SETUP_H
 
-#define COMMAND_LINE_SIZE	256
+#define COMMAND_LINE_SIZE	CONFIG_COMMAND_LINE_SIZE
 
 #endif