[PATCH] Dynamic kernel command-line: common

Current implementation stores a static command-line buffer allocated to
COMMAND_LINE_SIZE size.  Most architectures stores two copies of this buffer,
one for future reference and one for parameter parsing.

Current kernel command-line size for most architecture is much too small for
module parameters, video settings, initramfs paramters and much more.  The
problem is that setting COMMAND_LINE_SIZE to a grater value, allocates static
buffers.

In order to allow a greater command-line size, these buffers should be
dynamically allocated or marked as init disposable buffers, so unused memory
can be released.

This patch renames the static saved_command_line variable into
boot_command_line adding __initdata attribute, so that it can be disposed
after initialization.  This rename is required so applications that use
saved_command_line will not be affected by this change.

It reintroduces saved_command_line as dynamically allocated buffer to match
the data in boot_command_line.

It also mark secondary command-line buffer as __initdata, and copies it to
dynamically allocated static_command_line buffer components may hold reference
to it after initialization.

This patch is for linux-2.6.20-rc4-mm1 and is divided to target each
architecture.  I could not check this in any architecture so please forgive me
if I got it wrong.

The per-architecture modification is very simple, use boot_command_line in
place of saved_command_line.  The common code is the change into dynamic
command-line.

This patch:

1. Rename saved_command_line into boot_command_line, mark as init
   disposable.

2. Add dynamic allocated saved_command_line.

3. Add dynamic allocated static_command_line.

4. During startup copy: boot_command_line into saved_command_line.  arch
   command_line into static_command_line.

5. Parse static_command_line and not arch command_line, so arch
   command_line may be freed.

Signed-off-by: Alon Bar-Lev <alon.barlev@gmail.com>
Cc: Andi Kleen <ak@muc.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Ian Molton <spyro@f2s.com>
Cc: Mikael Starvik <starvik@axis.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Kyle McMartin <kyle@mcmartin.ca>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Hirokazu Takata <takata@linux-m32r.org>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Kazumoto Kojima <kkojima@rr.iij4u.or.jp>
Cc: Richard Curnow <rc@rc0.org.uk>
Cc: William Lee Irwin III <wli@holomorphy.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jeff Dike <jdike@addtoit.com>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Cc: Miles Bader <uclinux-v850@lsi.nec.co.jp>
Cc: Chris Zankel <chris@zankel.net>
Cc: "Luck, Tony" <tony.luck@intel.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Roman Zippel <zippel@linux-m68k.org>
Cc: Greg Ungerer <gerg@uclinux.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 27 insertions, 7 deletions

diff --git a/include/linux/init.h b/include/linux/init.h
index c65f5107d51..e290a010e3f 100644
--- a/include/linux/init.h
+++ b/include/linux/init.h
@@ -67,7 +67,8 @@ extern initcall_t __con_initcall_start[], __con_initcall_end[];
 extern initcall_t __security_initcall_start[], __security_initcall_end[];
 
 /* Defined in init/main.c */
-extern char saved_command_line[];
+extern char __initdata boot_command_line[];
+extern char *saved_command_line;
 extern unsigned int reset_devices;
 
 /* used by init/main.c */
@@ -164,7 +165,7 @@ struct obs_kernel_param {
 #define early_param(str, fn)					\
 	__setup_param(str, fn, fn, 1)
 
-/* Relies on saved_command_line being set */
+/* Relies on boot_command_line being set */
 void __init parse_early_param(void);
 #endif /* __ASSEMBLY__ */
 
diff --git a/init/main.c b/init/main.c
index 4e88bddfbeb..4e9e92bb2b8 100644
--- a/init/main.c
+++ b/init/main.c
@@ -121,8 +121,12 @@ extern void time_init(void);
 void (*late_time_init)(void);
 extern void softirq_init(void);
 
-/* Untouched command line (eg. for /proc) saved by arch-specific code. */
-char saved_command_line[COMMAND_LINE_SIZE];
+/* Untouched command line saved by arch-specific code. */
+char __initdata boot_command_line[COMMAND_LINE_SIZE];
+/* Untouched saved command line (eg. for /proc) */
+char *saved_command_line;
+/* Command line for parameter parsing */
+static char *static_command_line;
 
 static char *execute_command;
 static char *ramdisk_execute_command;
@@ -400,6 +404,20 @@ static void __init smp_init(void)
 #endif
 
 /*
+ * We need to store the untouched command line for future reference.
+ * We also need to store the touched command line since the parameter
+ * parsing is performed in place, and we should allow a component to
+ * store reference of name/value for future reference.
+ */
+static void __init setup_command_line(char *command_line)
+{
+	saved_command_line = alloc_bootmem(strlen (boot_command_line)+1);
+	static_command_line = alloc_bootmem(strlen (command_line)+1);
+	strcpy (saved_command_line, boot_command_line);
+	strcpy (static_command_line, command_line);
+}
+
+/*
  * We need to finalize in a non-__init function or else race conditions
  * between the root thread and the init thread may cause start_kernel to
  * be reaped by free_initmem before the root thread has proceeded to
@@ -453,7 +471,7 @@ void __init parse_early_param(void)
 		return;
 
 	/* All fall through to do_early_param. */
-	strlcpy(tmp_cmdline, saved_command_line, COMMAND_LINE_SIZE);
+	strlcpy(tmp_cmdline, boot_command_line, COMMAND_LINE_SIZE);
 	parse_args("early options", tmp_cmdline, NULL, 0, do_early_param);
 	done = 1;
 }
@@ -503,6 +521,7 @@ asmlinkage void __init start_kernel(void)
 	printk(KERN_NOTICE);
 	printk(linux_banner);
 	setup_arch(&command_line);
+	setup_command_line(command_line);
 	unwind_setup();
 	setup_per_cpu_areas();
 	smp_prepare_boot_cpu();	/* arch-specific boot-cpu hooks */
@@ -520,9 +539,9 @@ asmlinkage void __init start_kernel(void)
 	preempt_disable();
 	build_all_zonelists();
 	page_alloc_init();
-	printk(KERN_NOTICE "Kernel command line: %s\n", saved_command_line);
+	printk(KERN_NOTICE "Kernel command line: %s\n", boot_command_line);
 	parse_early_param();
-	parse_args("Booting kernel", command_line, __start___param,
+	parse_args("Booting kernel", static_command_line, __start___param,
 		   __stop___param - __start___param,
 		   &unknown_bootoption);
 	if (!irqs_disabled()) {