Re: [PATCH -v2] MIPS: add support for gzip/bzip2/lzma compressed kernel images

[Wu Zhangjin <wuzhangjin@gmail.com>]

On Tue, 2009-10-13 at 00:05 +0800, Wu Zangjin wrote:
> From: Wu Zhangjin <wuzhangjin@gmail.com>
> 
> This patch will help to generate smaller kernel images for linux-MIPS,
> 
> Here is the effect when using lzma:
> 
> $ ls -sh vmlinux
> 7.1M vmlinux
> $ ls -sh arch/mips/boot/compressed/vmlinuz
> 1.5M arch/mips/boot/compressed/vmlinuz
> 

The above message is out-of-date, the path of vmlinuz have been changed
to the root directory linux, it should be:

$ ls -sh vmlinux  (original)
6.0M vmlinux
$ ls -sh vmlinuz (lzma)
1.2M vmlinuz
$ ls -sh vmlinuz (bzip2)
1.5M vmlinuz
$ ls -sh vmlinuz (gzip)
1.6M vmlinuz

> Have tested the 32bit kernel on Qemu/Malta and 64bit kernel on FuLoong
> Mini PC. both of them work well. and also, tested by Alexander Clouter
> on an AR7 based Linksys WAG54Gv2, and by Manuel Lauss on an Alchemy
> board.
> 
> This -v2 version incorporate the feedback from Ralf, and add the
> following changes:
> 
> 1. add .ecoff, .bin, .erec format support
> 2. only enable it and the debug source code for the machines we tested
> 3. a dozens of fixups and cleanups
> 
> and if you want to enable it for your board, please try to select
> SYS_SUPPORTS_ZBOOT for it, and if the board have an 16550 compatible
> uart, you can select SYS_SUPPORTS_ZBOOT_UART16550 directly. and then
> sending the relative patches to Ralf.
> 
> Tested-by: Manuel Lauss <manuel.lauss@googlemail.com>
> Signed-off-by: Alexander Clouter <alex@digriz.org.uk>
> Signed-off-by: Wu Zhangjin <wuzhangjin@gmail.com>
> ---
>  arch/mips/Kconfig                      |   14 +++
>  arch/mips/Makefile                     |   31 ++++++-
>  arch/mips/boot/compressed/Makefile     |  100 +++++++++++++++++++++
>  arch/mips/boot/compressed/dbg.c        |   37 ++++++++
>  arch/mips/boot/compressed/decompress.c |  126 +++++++++++++++++++++++++++
>  arch/mips/boot/compressed/dummy.c      |    4 +
>  arch/mips/boot/compressed/head.S       |   55 ++++++++++++
>  arch/mips/boot/compressed/ld.script    |  150 ++++++++++++++++++++++++++++++++
>  arch/mips/boot/compressed/uart-16550.c |   43 +++++++++
>  9 files changed, 557 insertions(+), 3 deletions(-)
>  create mode 100644 arch/mips/boot/compressed/Makefile
>  create mode 100644 arch/mips/boot/compressed/dbg.c
>  create mode 100644 arch/mips/boot/compressed/decompress.c
>  create mode 100644 arch/mips/boot/compressed/dummy.c
>  create mode 100644 arch/mips/boot/compressed/head.S
>  create mode 100644 arch/mips/boot/compressed/ld.script
>  create mode 100644 arch/mips/boot/compressed/uart-16550.c
> 
> diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
> index 9da6a52..96bb02d 100644
> --- a/arch/mips/Kconfig
> +++ b/arch/mips/Kconfig
> @@ -21,6 +21,7 @@ choice
>  
>  config MACH_ALCHEMY
>  	bool "Alchemy processor based machines"
> +	select SYS_SUPPORTS_ZBOOT
>  
>  config AR7
>  	bool "Texas Instruments AR7"
> @@ -35,6 +36,7 @@ config AR7
>  	select SYS_HAS_EARLY_PRINTK
>  	select SYS_SUPPORTS_32BIT_KERNEL
>  	select SYS_SUPPORTS_LITTLE_ENDIAN
> +	select SYS_SUPPORTS_ZBOOT_UART16550
>  	select GENERIC_GPIO
>  	select GCD
>  	select VLYNQ
> @@ -191,6 +193,7 @@ config LASAT
>  
>  config MACH_LOONGSON
>  	bool "Loongson family of machines"
> +	select SYS_SUPPORTS_ZBOOT_UART16550
>  	help
>  	  This enables the support of Loongson family of machines.
>  
> @@ -232,6 +235,7 @@ config MIPS_MALTA
>  	select SYS_SUPPORTS_MIPS_CMP
>  	select SYS_SUPPORTS_MULTITHREADING
>  	select SYS_SUPPORTS_SMARTMIPS
> +	select SYS_SUPPORTS_ZBOOT
>  	help
>  	  This enables support for the MIPS Technologies Malta evaluation
>  	  board.
> @@ -1294,6 +1298,16 @@ config CPU_CAVIUM_OCTEON
>  
>  endchoice
>  
> +config SYS_SUPPORTS_ZBOOT
> +	bool
> +	select HAVE_KERNEL_GZIP
> +	select HAVE_KERNEL_BZIP2
> +	select HAVE_KERNEL_LZMA
> +
> +config SYS_SUPPORTS_ZBOOT_UART16550
> +	bool
> +	select SYS_SUPPORTS_ZBOOT
> +
>  config CPU_LOONGSON2
>  	bool
>  	select CPU_SUPPORTS_32BIT_KERNEL
> diff --git a/arch/mips/Makefile b/arch/mips/Makefile
> index d45e596..ccd713d 100644
> --- a/arch/mips/Makefile
> +++ b/arch/mips/Makefile
> @@ -69,6 +69,7 @@ endif
>  
>  all-$(CONFIG_BOOT_ELF32)	:= $(vmlinux-32)
>  all-$(CONFIG_BOOT_ELF64)	:= $(vmlinux-64)
> +all-$(CONFIG_SYS_SUPPORTS_ZBOOT)+= vmlinuz
>  
>  #
>  # GCC uses -G 0 -mabicalls -fpic as default.  We don't want PIC in the kernel
> @@ -336,7 +337,7 @@ load-$(CONFIG_LEMOTE_YEELOONG2F) +=0xffffffff80200000
>  core-$(CONFIG_MIPS_MALTA)	+= arch/mips/mti-malta/
>  cflags-$(CONFIG_MIPS_MALTA)	+= -I$(srctree)/arch/mips/include/asm/mach-malta
>  load-$(CONFIG_MIPS_MALTA)	+= 0xffffffff80100000
> -all-$(CONFIG_MIPS_MALTA)	:= vmlinux.bin
> +all-$(CONFIG_MIPS_MALTA)	:= vmlinuz.bin
>  
>  #
>  # MIPS SIM
> @@ -586,7 +587,7 @@ load-$(CONFIG_SNI_RM)		+= 0xffffffff80600000
>  else
>  load-$(CONFIG_SNI_RM)		+= 0xffffffff80030000
>  endif
> -all-$(CONFIG_SNI_RM)		:= vmlinux.ecoff
> +all-$(CONFIG_SNI_RM)		:= vmlinuz.ecoff
>  
>  #
>  # Common TXx9
> @@ -704,9 +705,23 @@ vmlinux.64: vmlinux
>  	$(OBJCOPY) -O $(64bit-bfd) $(OBJCOPYFLAGS) $< $@
>  
>  makeboot =$(Q)$(MAKE) $(build)=arch/mips/boot VMLINUX=$(vmlinux-32) $(1)
> +makezboot =$(Q)$(MAKE) $(build)=arch/mips/boot/compressed \
> +	   VMLINUX_LOAD_ADDRESS=$(load-y) 32bit-bfd=$(32bit-bfd) $(1)
>  
>  all:	$(all-y)
>  
> +vmlinuz: vmlinux
> +	+@$(call makezboot,$@)
> +
> +vmlinuz.bin: vmlinux
> +	+@$(call makezboot,$@)
> +
> +vmlinuz.ecoff: vmlinux
> +	+@$(call makezboot,$@)
> +
> +vmlinuz.srec: vmlinux
> +	+@$(call makezboot,$@)
> +
>  vmlinux.bin: $(vmlinux-32)
>  	+@$(call makeboot,$@)
>  
> @@ -731,11 +746,13 @@ endif
>  
>  install:
>  	$(Q)install -D -m 755 vmlinux $(INSTALL_PATH)/vmlinux-$(KERNELRELEASE)
> +	$(Q)install -D -m 755 vmlinuz $(INSTALL_PATH)/vmlinuz-$(KERNELRELEASE)
>  	$(Q)install -D -m 644 .config $(INSTALL_PATH)/config-$(KERNELRELEASE)
>  	$(Q)install -D -m 644 System.map $(INSTALL_PATH)/System.map-$(KERNELRELEASE)
>  
>  archclean:
>  	@$(MAKE) $(clean)=arch/mips/boot
> +	@$(MAKE) $(clean)=arch/mips/boot/compressed
>  	@$(MAKE) $(clean)=arch/mips/lasat
>  
>  define archhelp
> @@ -743,10 +760,18 @@ define archhelp
>  	echo '  vmlinux.ecoff        - ECOFF boot image'
>  	echo '  vmlinux.bin          - Raw binary boot image'
>  	echo '  vmlinux.srec         - SREC boot image'
> +	echo '  vmlinuz              - Compressed boot(zboot) image'
> +	echo '  vmlinuz.ecoff        - ECOFF zboot image'
> +	echo '  vmlinuz.bin          - Raw binary zboot image'
> +	echo '  vmlinuz.srec         - SREC zboot image'
>  	echo
>  	echo '  These will be default as apropriate for a configured platform.'
>  endef
>  
>  CLEAN_FILES += vmlinux.32 \
>  	       vmlinux.64 \
> -	       vmlinux.ecoff
> +	       vmlinux.ecoff \
> +	       vmlinuz \
> +	       vmlinuz.ecoff \
> +	       vmlinuz.bin \
> +	       vmlinuz.srec
> diff --git a/arch/mips/boot/compressed/Makefile b/arch/mips/boot/compressed/Makefile
> new file mode 100644
> index 0000000..140bd9b
> --- /dev/null
> +++ b/arch/mips/boot/compressed/Makefile
> @@ -0,0 +1,100 @@
> +#
> +# This file is subject to the terms and conditions of the GNU General Public
> +# License.
> +#
> +# Adapted for MIPS Pete Popov, Dan Malek
> +#
> +# Copyright (C) 1994 by Linus Torvalds
> +# Adapted for PowerPC by Gary Thomas
> +# modified by Cort (cort@cs.nmt.edu)
> +#
> +# Copyright (C) 2009 Lemote Inc. & DSLab, Lanzhou University
> +# Author: Wu Zhangjin <wuzj@lemote.com>
> +#
> +
> +# compressed kernel load addr: VMLINUZ_LOAD_ADDRESS > VMLINUX_LOAD_ADDRESS + VMLINUX_SIZE
> +VMLINUX_SIZE := $(shell wc -c $(objtree)/$(KBUILD_IMAGE) 2>/dev/null | cut -d' ' -f1)
> +VMLINUX_SIZE := $(shell [ -n "$(VMLINUX_SIZE)" ] && echo $$(($(VMLINUX_SIZE) + (65536 - $(VMLINUX_SIZE) % 65536))))
> +VMLINUZ_LOAD_ADDRESS := 0x$(shell [ -n "$(VMLINUX_SIZE)" ] && printf %x $$(($(VMLINUX_LOAD_ADDRESS) + $(VMLINUX_SIZE))))
> +
> +# set the default size of the mallocing area for decompressing
> +BOOT_HEAP_SIZE := 0x400000
> +
> +KBUILD_CFLAGS := $(LINUXINCLUDE) $(KBUILD_CFLAGS) -D__KERNEL__ \
> +	-DBOOT_HEAP_SIZE=$(BOOT_HEAP_SIZE) -D"VMLINUX_LOAD_ADDRESS_ULL=$(VMLINUX_LOAD_ADDRESS)ull" \
> +
> +KBUILD_AFLAGS := $(LINUXINCLUDE) $(KBUILD_AFLAGS) -D__ASSEMBLY__ \
> +	-DKERNEL_ENTRY=0x$(shell $(NM) $(objtree)/$(KBUILD_IMAGE) 2>/dev/null | grep " kernel_entry" | cut -f1 -d \ ) \
> +	-DBOOT_HEAP_SIZE=$(BOOT_HEAP_SIZE)
> +
> +obj-y := $(obj)/head.o $(obj)/decompress.o $(obj)/dbg.o
> +
> +obj-$(CONFIG_SYS_SUPPORTS_ZBOOT_UART16550) += $(obj)/uart-16550.o
> +
> +OBJCOPYFLAGS_vmlinux.bin := $(OBJCOPYFLAGS) -O binary -R .comment -S
> +$(obj)/vmlinux.bin: $(KBUILD_IMAGE)
> +	$(call if_changed,objcopy)
> +
> +suffix_$(CONFIG_KERNEL_GZIP)  = gz
> +suffix_$(CONFIG_KERNEL_BZIP2) = bz2
> +suffix_$(CONFIG_KERNEL_LZMA)  = lzma
> +tool_$(CONFIG_KERNEL_GZIP)    = gzip
> +tool_$(CONFIG_KERNEL_BZIP2)   = bzip2
> +tool_$(CONFIG_KERNEL_LZMA)    = lzma
> +$(obj)/vmlinux.$(suffix_y): $(obj)/vmlinux.bin
> +	$(call if_changed,$(tool_y))
> +	$(Q)rm -f $<
> +
> +$(obj)/piggy.o: $(obj)/vmlinux.$(suffix_y) $(obj)/dummy.o
> +	$(Q)$(OBJCOPY) $(OBJCOPYFLAGS) \
> +		--add-section=.image=$< \
> +		--set-section-flags=.image=contents,alloc,load,readonly,data \
> +		$(obj)/dummy.o $@
> +	$(Q)rm -f $<
> +
> +LDFLAGS_vmlinuz := $(LDFLAGS) -Ttext $(VMLINUZ_LOAD_ADDRESS) -T
> +vmlinuz: $(src)/ld.script $(obj-y) $(obj)/piggy.o
> +	$(call if_changed,ld)
> +	$(Q)$(OBJCOPY) $(OBJCOPYFLAGS) -R .comment -R .stab -R .stabstr -R .initrd -R .sysmap $@
> +	$(Q)rm -f $(obj)/piggy.o
> +
> +#
> +# Some DECstations need all possible sections of an ECOFF executable
> +#
> +ifdef CONFIG_MACH_DECSTATION
> +  E2EFLAGS = -a
> +else
> +  E2EFLAGS =
> +endif
> +
> +# elf2ecoff can only handle 32bit image
> +
> +ifdef CONFIG_32BIT
> +	VMLINUZ = vmlinuz
> +else
> +	VMLINUZ = vmlinuz.32
> +endif
> +
> +vmlinuz.32: vmlinuz
> +	$(Q)$(OBJCOPY) -O $(32bit-bfd) $(OBJCOPYFLAGS) $< $@
> +
> +vmlinuz.ecoff: $(obj)/../elf2ecoff $(VMLINUZ)
> +	$(Q)$(obj)/../elf2ecoff $(VMLINUZ) vmlinuz.ecoff $(E2EFLAGS)
> +
> +$(obj)/../elf2ecoff: $(src)/../elf2ecoff.c
> +	$(Q)$(HOSTCC) -o $@ $^
> +
> +drop-sections	= .reginfo .mdebug .comment .note .pdr .options .MIPS.options
> +strip-flags	= $(addprefix --remove-section=,$(drop-sections))
> +
> +OBJCOPYFLAGS_vmlinuz.bin := $(OBJCOPYFLAGS) -O binary $(strip-flags)
> +vmlinuz.bin: vmlinuz
> +	$(call if_changed,objcopy)
> +
> +OBJCOPYFLAGS_vmlinuz.srec := $(OBJCOPYFLAGS) -S -O srec $(strip-flags)
> +vmlinuz.srec: vmlinuz
> +	$(call if_changed,objcopy)
> +
> +clean:
> +clean-files += *.o \
> +	       vmlinu*
> diff --git a/arch/mips/boot/compressed/dbg.c b/arch/mips/boot/compressed/dbg.c
> new file mode 100644
> index 0000000..ff4dc7a
> --- /dev/null
> +++ b/arch/mips/boot/compressed/dbg.c
> @@ -0,0 +1,37 @@
> +/*
> + * MIPS-specific debug support for pre-boot environment
> + *
> + * NOTE: putc() is board specific, if your board have a 16550 compatible uart,
> + * please select SYS_SUPPORTS_ZBOOT_UART16550 for your machine. othewise, you
> + * need to implement your own putc().
> + */
> +
> +#include <linux/init.h>
> +#include <linux/types.h>
> +
> +void __attribute__ ((weak)) putc(char c)
> +{
> +}
> +
> +void puts(const char *s)
> +{
> +	char c;
> +	while ((c = *s++) != '\0') {
> +		putc(c);
> +		if (c == '\n')
> +			putc('\r');
> +	}
> +}
> +
> +void puthex(unsigned long long val)
> +{
> +
> +	unsigned char buf[10];
> +	int i;
> +	for (i = 7; i >= 0; i--) {
> +		buf[i] = "0123456789ABCDEF"[val & 0x0F];
> +		val >>= 4;
> +	}
> +	buf[8] = '\0';
> +	puts(buf);
> +}
> diff --git a/arch/mips/boot/compressed/decompress.c b/arch/mips/boot/compressed/decompress.c
> new file mode 100644
> index 0000000..67330c2
> --- /dev/null
> +++ b/arch/mips/boot/compressed/decompress.c
> @@ -0,0 +1,126 @@
> +/*
> + * Misc. bootloader code for many machines.
> + *
> + * Copyright 2001 MontaVista Software Inc.
> + * Author: Matt Porter <mporter@mvista.com> Derived from
> + * arch/ppc/boot/prep/misc.c
> + *
> + * Copyright (C) 2009 Lemote, Inc. & Institute of Computing Technology
> + * Author: Wu Zhangjin <wuzj@lemote.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.
> + */
> +
> +#include <linux/types.h>
> +#include <linux/kernel.h>
> +
> +#include <asm/addrspace.h>
> +
> +/* These two variables specify the free mem region
> + * that can be used for temporary malloc area
> + */
> +unsigned long free_mem_ptr;
> +unsigned long free_mem_end_ptr;
> +char *zimage_start;
> +
> +/* The linker tells us where the image is. */
> +extern unsigned char __image_begin, __image_end;
> +extern unsigned char __ramdisk_begin, __ramdisk_end;
> +unsigned long initrd_size;
> +
> +/* debug interfaces  */
> +extern void puts(const char *s);
> +extern void puthex(unsigned long long val);
> +
> +void error(char *x)
> +{
> +	puts("\n\n");
> +	puts(x);
> +	puts("\n\n -- System halted");
> +
> +	while (1)
> +		;	/* Halt */
> +}
> +
> +/* activate the code for pre-boot environment */
> +#define STATIC static
> +
> +#ifdef CONFIG_KERNEL_GZIP
> +void *memcpy(void *dest, const void *src, size_t n)
> +{
> +	int i;
> +	const char *s = src;
> +	char *d = dest;
> +
> +	for (i = 0; i < n; i++)
> +		d[i] = s[i];
> +	return dest;
> +}
> +#include "../../../../lib/decompress_inflate.c"
> +#endif
> +
> +#ifdef CONFIG_KERNEL_BZIP2
> +void *memset(void *s, int c, size_t n)
> +{
> +	int i;
> +	char *ss = s;
> +
> +	for (i = 0; i < n; i++)
> +		ss[i] = c;
> +	return s;
> +}
> +#include "../../../../lib/decompress_bunzip2.c"
> +#endif
> +
> +#ifdef CONFIG_KERNEL_LZMA
> +#include "../../../../lib/decompress_unlzma.c"
> +#endif
> +
> +void decompress_kernel(unsigned long boot_heap_start)
> +{
> +	int zimage_size;
> +
> +	/*
> +	 * We link ourself to an arbitrary low address.  When we run, we
> +	 * relocate outself to that address.  __image_beign points to
> +	 * the part of the image where the zImage is. -- Tom
> +	 */
> +	zimage_start = (char *)(unsigned long)(&__image_begin);
> +	zimage_size = (unsigned long)(&__image_end) -
> +	    (unsigned long)(&__image_begin);
> +
> +	/*
> +	 * The zImage and initrd will be between start and _end, so they've
> +	 * already been moved once.  We're good to go now. -- Tom
> +	 */
> +	puts("zimage at:     ");
> +	puthex((unsigned long)zimage_start);
> +	puts(" ");
> +	puthex((unsigned long)(zimage_size + zimage_start));
> +	puts("\n");
> +
> +	if (initrd_size) {
> +		puts("initrd at:     ");
> +		puthex((unsigned long)(&__ramdisk_begin));
> +		puts(" ");
> +		puthex((unsigned long)(&__ramdisk_end));
> +		puts("\n");
> +	}
> +
> +	/* this area are prepared for mallocing when decompressing */
> +	free_mem_ptr = boot_heap_start;
> +	free_mem_end_ptr = boot_heap_start + BOOT_HEAP_SIZE;
> +
> +	/* Display standard Linux/MIPS boot prompt for kernel args */
> +	puts("Uncompressing Linux at load address ");
> +	puthex(VMLINUX_LOAD_ADDRESS_ULL);
> +	puts("\n");
> +	/* Decompress the kernel with according algorithm */
> +	decompress(zimage_start, zimage_size, 0, 0,
> +		   (void *)VMLINUX_LOAD_ADDRESS_ULL, 0, error);
> +	/* FIXME: is there a need to flush cache here? */
> +	puts("Now, booting the kernel...\n");
> +}
> diff --git a/arch/mips/boot/compressed/dummy.c b/arch/mips/boot/compressed/dummy.c
> new file mode 100644
> index 0000000..31dbf45
> --- /dev/null
> +++ b/arch/mips/boot/compressed/dummy.c
> @@ -0,0 +1,4 @@
> +int main(void)
> +{
> +	return 0;
> +}
> diff --git a/arch/mips/boot/compressed/head.S b/arch/mips/boot/compressed/head.S
> new file mode 100644
> index 0000000..e23f25e
> --- /dev/null
> +++ b/arch/mips/boot/compressed/head.S
> @@ -0,0 +1,55 @@
> +/*
> + * This file is subject to the terms and conditions of the GNU General Public
> + * License.  See the file "COPYING" in the main directory of this archive
> + * for more details.
> + *
> + * Copyright (C) 1994, 1995 Waldorf Electronics
> + * Written by Ralf Baechle and Andreas Busse
> + * Copyright (C) 1995 - 1999 Ralf Baechle
> + * Copyright (C) 1996 Paul M. Antoine
> + * Modified for DECStation and hence R3000 support by Paul M. Antoine
> + * Further modifications by David S. Miller and Harald Koerfgen
> + * Copyright (C) 1999 Silicon Graphics, Inc.
> + */
> +
> +#include <asm/asm.h>
> +#include <asm/regdef.h>
> +
> +	.set noreorder
> +	.cprestore
> +	LEAF(start)
> +start:
> +	/* Save boot rom start args */
> +	move	s0, a0
> +	move	s1, a1
> +	move	s2, a2
> +	move	s3, a3
> +
> +	/* Clear BSS */
> +	PTR_LA	a0, _edata
> +	PTR_LA	a2, _end
> +1:	sw	zero, 0(a0)
> +	bne	a2, a0, 1b
> +	addu	a0, 4
> +
> +	PTR_LA	a0, (.heap)          /* heap address */
> +	PTR_LA  sp, (.stack + 8192)  /* stack address */
> +
> +	PTR_LA	ra, 2f
> +	PTR_LA	k0, decompress_kernel
> +	jr	k0
> +	nop
> +2:
> +	move	a0, s0
> +	move	a1, s1
> +	move	a2, s2
> +	move	a3, s3
> +	PTR_LI	k0, KERNEL_ENTRY
> +	jr	k0
> +	nop
> +3:
> +	b 3b
> +	END(start)
> +
> +	.comm .heap,BOOT_HEAP_SIZE,4
> +	.comm .stack,4096*2,4
> diff --git a/arch/mips/boot/compressed/ld.script b/arch/mips/boot/compressed/ld.script
> new file mode 100644
> index 0000000..29e9f4c
> --- /dev/null
> +++ b/arch/mips/boot/compressed/ld.script
> @@ -0,0 +1,150 @@
> +OUTPUT_ARCH(mips)
> +ENTRY(start)
> +SECTIONS
> +{
> +  /* Read-only sections, merged into text segment: */
> +  .init          : { *(.init)		} =0
> +  .text      :
> +  {
> +    _ftext = . ;
> +    *(.text)
> +    *(.rodata)
> +    *(.rodata1)
> +    /* .gnu.warning sections are handled specially by elf32.em.  */
> +    *(.gnu.warning)
> +  } =0
> +  .kstrtab : { *(.kstrtab) }
> +
> +  . = ALIGN(16);		/* Exception table */
> +  __start___ex_table = .;
> +  __ex_table : { *(__ex_table) }
> +  __stop___ex_table = .;
> +
> +  __start___dbe_table = .;	/* Exception table for data bus errors */
> +  __dbe_table : { *(__dbe_table) }
> +  __stop___dbe_table = .;
> +
> +  __start___ksymtab = .;	/* Kernel symbol table */
> +  __ksymtab : { *(__ksymtab) }
> +  __stop___ksymtab = .;
> +
> +  _etext = .;
> +
> +  . = ALIGN(8192);
> +  .data.init_task : { *(.data.init_task) }
> +
> +  /* Startup code */
> +  . = ALIGN(4096);
> +  __init_begin = .;
> +  .text.init : { *(.text.init) }
> +  .data.init : { *(.data.init) }
> +  . = ALIGN(16);
> +  __setup_start = .;
> +  .setup.init : { *(.setup.init) }
> +  __setup_end = .;
> +  __initcall_start = .;
> +  .initcall.init : { *(.initcall.init) }
> +  __initcall_end = .;
> +  . = ALIGN(4096);	/* Align double page for init_task_union */
> +  __init_end = .;
> +
> +  . = ALIGN(4096);
> +  .data.page_aligned : { *(.data.idt) }
> +
> +  . = ALIGN(32);
> +  .data.cacheline_aligned : { *(.data.cacheline_aligned) }
> +
> +  .fini      : { *(.fini)    } =0
> +  .reginfo : { *(.reginfo) }
> +  /* Adjust the address for the data segment.  We want to adjust up to
> +     the same address within the page on the next page up.  It would
> +     be more correct to do this:
> +       . = .;
> +     The current expression does not correctly handle the case of a
> +     text segment ending precisely at the end of a page; it causes the
> +     data segment to skip a page.  The above expression does not have
> +     this problem, but it will currently (2/95) cause BFD to allocate
> +     a single segment, combining both text and data, for this case.
> +     This will prevent the text segment from being shared among
> +     multiple executions of the program; I think that is more
> +     important than losing a page of the virtual address space (note
> +     that no actual memory is lost; the page which is skipped can not
> +     be referenced).  */
> +  . = .;
> +  .data    :
> +  {
> +    _fdata = . ;
> +    *(.data)
> +
> +   /* Put the compressed image here, so bss is on the end. */
> +   __image_begin = .;
> +   *(.image)
> +   __image_end = .;
> +   /* Align the initial ramdisk image (INITRD) on page boundaries. */
> +   . = ALIGN(4096);
> +   __ramdisk_begin = .;
> +   *(.initrd)
> +   __ramdisk_end = .;
> +   . = ALIGN(4096);
> +
> +    CONSTRUCTORS
> +  }
> +  .data1   : { *(.data1) }
> +  _gp = . + 0x8000;
> +  .lit8 : { *(.lit8) }
> +  .lit4 : { *(.lit4) }
> +  .ctors         : { *(.ctors)   }
> +  .dtors         : { *(.dtors)   }
> +  .got           : { *(.got.plt) *(.got) }
> +  .dynamic       : { *(.dynamic) }
> +  /* We want the small data sections together, so single-instruction offsets
> +     can access them all, and initialized data all before uninitialized, so
> +     we can shorten the on-disk segment size.  */
> +  .sdata     : { *(.sdata) }
> +  . = ALIGN(4);
> +  _edata  =  .;
> +  PROVIDE (edata = .);
> +
> +  __bss_start = .;
> +  _fbss = .;
> +  .sbss      : { *(.sbss) *(.scommon) }
> +  .bss       :
> +  {
> +   *(.dynbss)
> +   *(.bss)
> +   *(COMMON)
> +   .  = ALIGN(4);
> +  _end = . ;
> +  PROVIDE (end = .);
> +  }
> +
> +  /* Sections to be discarded */
> +  /DISCARD/ :
> +  {
> +        *(.text.exit)
> +        *(.data.exit)
> +        *(.exitcall.exit)
> +  }
> +
> +  /* This is the MIPS specific mdebug section.  */
> +  .mdebug : { *(.mdebug) }
> +  /* These are needed for ELF backends which have not yet been
> +     converted to the new style linker.  */
> +  .stab 0 : { *(.stab) }
> +  .stabstr 0 : { *(.stabstr) }
> +  /* DWARF debug sections.
> +     Symbols in the .debug DWARF section are relative to the beginning of the
> +     section so we begin .debug at 0.  It's not clear yet what needs to happen
> +     for the others.   */
> +  .debug          0 : { *(.debug) }
> +  .debug_srcinfo  0 : { *(.debug_srcinfo) }
> +  .debug_aranges  0 : { *(.debug_aranges) }
> +  .debug_pubnames 0 : { *(.debug_pubnames) }
> +  .debug_sfnames  0 : { *(.debug_sfnames) }
> +  .line           0 : { *(.line) }
> +  /* These must appear regardless of  .  */
> +  .gptab.sdata : { *(.gptab.data) *(.gptab.sdata) }
> +  .gptab.sbss : { *(.gptab.bss) *(.gptab.sbss) }
> +  .comment : { *(.comment) }
> +  .note : { *(.note) }
> +}
> diff --git a/arch/mips/boot/compressed/uart-16550.c b/arch/mips/boot/compressed/uart-16550.c
> new file mode 100644
> index 0000000..c9caaf4
> --- /dev/null
> +++ b/arch/mips/boot/compressed/uart-16550.c
> @@ -0,0 +1,43 @@
> +/*
> + * 16550 compatible uart based serial debug support for zboot
> + */
> +
> +#include <linux/types.h>
> +#include <linux/serial_reg.h>
> +#include <linux/init.h>
> +
> +#include <asm/addrspace.h>
> +
> +#if defined(CONFIG_MACH_LOONGSON) || defined(CONFIG_MIPS_MALTA)
> +#define UART_BASE 0x1fd003f8
> +#define PORT(offset) (CKSEG1ADDR(UART_BASE) + (offset))
> +#endif
> +
> +#ifdef CONFIG_AR7
> +#include <ar7.h>
> +#define PORT(offset) (CKSEG1ADDR(AR7_REGS_UART0) + (4 * offset))
> +#endif
> +
> +#ifndef PORT
> +#error please define the serial port address for your own machine
> +#endif
> +
> +static inline unsigned int serial_in(int offset)
> +{
> +	return *((char *)PORT(offset));
> +}
> +
> +static inline void serial_out(int offset, int value)
> +{
> +	*((char *)PORT(offset)) = value;
> +}
> +
> +void putc(char c)
> +{
> +	int timeout = 1024;
> +
> +	while (((serial_in(UART_LSR) & UART_LSR_THRE) == 0) && (timeout-- > 0))
> +		;
> +
> +	serial_out(UART_TX, c);
> +}