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    Subject[PATCH 10/12] i386: Relocatable kernel support


    This patch modifies the x86 kernel so that if CONFIG_RELOCATABLE is
    selected it will be able to be loaded at any 4K aligned address below
    1G. The technique used is to compile the decompressor with -fPIC and
    modify it so the decompressor is fully relocatable. For the main
    kernel relocations are generated. Resulting in a kernel that is relocatable
    with no runtime overhead and no need to modify the source code.

    A reserved 32bit word in the parameters has been assigned
    to serve as a stack so we figure out where are running.

    Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
    Signed-off-by: Vivek Goyal <vgoyal@in.ibm.com>
    ---

    arch/i386/Kconfig | 12
    arch/i386/Makefile | 4
    arch/i386/boot/compressed/Makefile | 22 +
    arch/i386/boot/compressed/head.S | 190 +++++++----
    arch/i386/boot/compressed/misc.c | 267 ++++++++--------
    arch/i386/boot/compressed/relocs.c | 563 ++++++++++++++++++++++++++++++++++
    arch/i386/boot/compressed/vmlinux.lds | 43 ++
    arch/i386/boot/compressed/vmlinux.scr | 3
    arch/i386/boot/setup.S | 29 +
    include/linux/screen_info.h | 3
    10 files changed, 920 insertions(+), 216 deletions(-)

    diff -puN arch/i386/boot/compressed/head.S~i386-Relocatable-kernel-support arch/i386/boot/compressed/head.S
    --- linux-2.6.18-git17/arch/i386/boot/compressed/head.S~i386-Relocatable-kernel-support 2006-10-02 14:09:14.000000000 -0400
    +++ linux-2.6.18-git17-root/arch/i386/boot/compressed/head.S 2006-10-02 14:33:13.000000000 -0400
    @@ -25,9 +25,11 @@

    #include <linux/linkage.h>
    #include <asm/segment.h>
    +#include <asm/page.h>

    +.section ".text.head"
    .globl startup_32
    -
    +
    startup_32:
    cld
    cli
    @@ -36,93 +38,141 @@ startup_32:
    movl %eax,%es
    movl %eax,%fs
    movl %eax,%gs
    + movl %eax,%ss

    - lss stack_start,%esp
    - xorl %eax,%eax
    -1: incl %eax # check that A20 really IS enabled
    - movl %eax,0x000000 # loop forever if it isn't
    - cmpl %eax,0x100000
    - je 1b
    +/* Calculate the delta between where we were compiled to run
    + * at and where we were actually loaded at. This can only be done
    + * with a short local call on x86. Nothing else will tell us what
    + * address we are running at. The reserved chunk of the real-mode
    + * data at 0x34-0x3f are used as the stack for this calculation.
    + * Only 4 bytes are needed.
    + */
    + leal 0x40(%esi), %esp
    + call 1f
    +1: popl %ebp
    + subl $1b, %ebp
    +
    +/* Compute the delta between where we were compiled to run at
    + * and where the code will actually run at.
    + */
    + /* Start with the delta to where the kernel will run at. If we are
    + * a relocatable kernel this is the delta to our load address otherwise
    + * this is the delta to CONFIG_PHYSICAL start.
    + */
    +#ifdef CONFIG_RELOCATABLE
    + movl %ebp, %ebx
    +#else
    + movl $(CONFIG_PHYSICAL_START - startup_32), %ebx
    +#endif
    +
    + /* Replace the compressed data size with the uncompressed size */
    + subl input_len(%ebp), %ebx
    + movl output_len(%ebp), %eax
    + addl %eax, %ebx
    + /* Add 8 bytes for every 32K input block */
    + shrl $12, %eax
    + addl %eax, %ebx
    + /* Add 32K + 18 bytes of extra slack */
    + addl $(32768 + 18), %ebx
    + /* Align on a 4K boundary */
    + addl $4095, %ebx
    + andl $~4095, %ebx
    +
    +/* Copy the compressed kernel to the end of our buffer
    + * where decompression in place becomes safe.
    + */
    + pushl %esi
    + leal _end(%ebp), %esi
    + leal _end(%ebx), %edi
    + movl $(_end - startup_32), %ecx
    + std
    + rep
    + movsb
    + cld
    + popl %esi
    +
    +/* Compute the kernel start address.
    + */
    +#ifdef CONFIG_RELOCATABLE
    + leal startup_32(%ebp), %ebp
    +#else
    + movl $CONFIG_PHYSICAL_START, %ebp
    +#endif

    /*
    - * Initialize eflags. Some BIOS's leave bits like NT set. This would
    - * confuse the debugger if this code is traced.
    - * XXX - best to initialize before switching to protected mode.
    + * Jump to the relocated address.
    */
    - pushl $0
    - popfl
    + leal relocated(%ebx), %eax
    + jmp *%eax
    +.section ".text"
    +relocated:
    +
    /*
    * Clear BSS
    */
    xorl %eax,%eax
    - movl $_edata,%edi
    - movl $_end,%ecx
    + leal _edata(%ebx),%edi
    + leal _end(%ebx), %ecx
    subl %edi,%ecx
    cld
    rep
    stosb
    +
    +/*
    + * Setup the stack for the decompressor
    + */
    + leal stack_end(%ebx), %esp
    +
    /*
    * Do the decompression, and jump to the new kernel..
    */
    - subl $16,%esp # place for structure on the stack
    - movl %esp,%eax
    + movl output_len(%ebx), %eax
    + pushl %eax
    + pushl %ebp # output address
    + movl input_len(%ebx), %eax
    + pushl %eax # input_len
    + leal input_data(%ebx), %eax
    + pushl %eax # input_data
    + leal _end(%ebx), %eax
    + pushl %eax # end of the image as third argument
    pushl %esi # real mode pointer as second arg
    - pushl %eax # address of structure as first arg
    call decompress_kernel
    - orl %eax,%eax
    - jnz 3f
    - popl %esi # discard address
    - popl %esi # real mode pointer
    - xorl %ebx,%ebx
    - ljmp $(__BOOT_CS), $CONFIG_PHYSICAL_START
    + addl $20, %esp
    + popl %ecx
    +
    +#if CONFIG_RELOCATABLE
    +/* Find the address of the relocations.
    + */
    + movl %ebp, %edi
    + addl %ecx, %edi
    +
    +/* Calculate the delta between where vmlinux was compiled to run
    + * and where it was actually loaded.
    + */
    + movl %ebp, %ebx
    + subl $CONFIG_PHYSICAL_START, %ebx

    /*
    - * We come here, if we were loaded high.
    - * We need to move the move-in-place routine down to 0x1000
    - * and then start it with the buffer addresses in registers,
    - * which we got from the stack.
    - */
    -3:
    - movl $move_routine_start,%esi
    - movl $0x1000,%edi
    - movl $move_routine_end,%ecx
    - subl %esi,%ecx
    - addl $3,%ecx
    - shrl $2,%ecx
    - cld
    - rep
    - movsl
    + * Process relocations.
    + */

    - popl %esi # discard the address
    - popl %ebx # real mode pointer
    - popl %esi # low_buffer_start
    - popl %ecx # lcount
    - popl %edx # high_buffer_start
    - popl %eax # hcount
    - movl $CONFIG_PHYSICAL_START,%edi
    - cli # make sure we don't get interrupted
    - ljmp $(__BOOT_CS), $0x1000 # and jump to the move routine
    -
    -/*
    - * Routine (template) for moving the decompressed kernel in place,
    - * if we were high loaded. This _must_ PIC-code !
    - */
    -move_routine_start:
    - movl %ecx,%ebp
    - shrl $2,%ecx
    - rep
    - movsl
    - movl %ebp,%ecx
    - andl $3,%ecx
    - rep
    - movsb
    - movl %edx,%esi
    - movl %eax,%ecx # NOTE: rep movsb won't move if %ecx == 0
    - addl $3,%ecx
    - shrl $2,%ecx
    - rep
    - movsl
    - movl %ebx,%esi # Restore setup pointer
    +1: subl $4, %edi
    + movl 0(%edi), %ecx
    + testl %ecx, %ecx
    + jz 2f
    + addl %ebx, -__PAGE_OFFSET(%ebx, %ecx)
    + jmp 1b
    +2:
    +#endif
    +
    +/*
    + * Jump to the decompressed kernel.
    + */
    xorl %ebx,%ebx
    - ljmp $(__BOOT_CS), $CONFIG_PHYSICAL_START
    -move_routine_end:
    + jmp *%ebp
    +
    +.bss
    +.balign 4
    +stack:
    + .fill 4096, 1, 0
    +stack_end:
    diff -puN arch/i386/boot/compressed/Makefile~i386-Relocatable-kernel-support arch/i386/boot/compressed/Makefile
    --- linux-2.6.18-git17/arch/i386/boot/compressed/Makefile~i386-Relocatable-kernel-support 2006-10-02 14:09:14.000000000 -0400
    +++ linux-2.6.18-git17-root/arch/i386/boot/compressed/Makefile 2006-10-02 14:09:14.000000000 -0400
    @@ -7,19 +7,33 @@
    targets := vmlinux vmlinux.bin vmlinux.bin.gz head.o misc.o piggy.o
    EXTRA_AFLAGS := -traditional

    -LDFLAGS_vmlinux := -Ttext $(IMAGE_OFFSET) -e startup_32
    +LDFLAGS_vmlinux := -T
    +CFLAGS_misc.o += -fPIC
    +hostprogs-y := relocs

    -$(obj)/vmlinux: $(obj)/head.o $(obj)/misc.o $(obj)/piggy.o FORCE
    +$(obj)/vmlinux: $(src)/vmlinux.lds $(obj)/head.o $(obj)/misc.o $(obj)/piggy.o FORCE
    $(call if_changed,ld)
    @:

    $(obj)/vmlinux.bin: vmlinux FORCE
    $(call if_changed,objcopy)

    -$(obj)/vmlinux.bin.gz: $(obj)/vmlinux.bin FORCE
    +quiet_cmd_relocs = RELOCS $@
    + cmd_relocs = $(obj)/relocs $< > $@
    +$(obj)/vmlinux.relocs: vmlinux $(obj)/relocs FORCE
    + $(call if_changed,relocs)
    +
    +vmlinux.bin.all-y := $(obj)/vmlinux.bin
    +vmlinux.bin.all-$(CONFIG_RELOCATABLE) += $(obj)/vmlinux.relocs
    +quiet_cmd_relocbin = BUILD $@
    + cmd_relocbin = cat $(filter-out FORCE,$^) > $@
    +$(obj)/vmlinux.bin.all: $(vmlinux.bin.all-y) FORCE
    + $(call if_changed,relocbin)
    +
    +$(obj)/vmlinux.bin.gz: $(obj)/vmlinux.bin.all FORCE
    $(call if_changed,gzip)

    LDFLAGS_piggy.o := -r --format binary --oformat elf32-i386 -T

    -$(obj)/piggy.o: $(obj)/vmlinux.scr $(obj)/vmlinux.bin.gz FORCE
    +$(obj)/piggy.o: $(src)/vmlinux.scr $(obj)/vmlinux.bin.gz FORCE
    $(call if_changed,ld)
    diff -puN arch/i386/boot/compressed/misc.c~i386-Relocatable-kernel-support arch/i386/boot/compressed/misc.c
    --- linux-2.6.18-git17/arch/i386/boot/compressed/misc.c~i386-Relocatable-kernel-support 2006-10-02 14:09:14.000000000 -0400
    +++ linux-2.6.18-git17-root/arch/i386/boot/compressed/misc.c 2006-10-02 14:33:13.000000000 -0400
    @@ -14,6 +14,88 @@
    #include <linux/vmalloc.h>
    #include <linux/screen_info.h>
    #include <asm/io.h>
    +#include <asm/page.h>
    +
    +/* WARNING!!
    + * This code is compiled with -fPIC and it is relocated dynamically
    + * at run time, but no relocation processing is performed.
    + * This means that it is not safe to place pointers in static structures.
    + */
    +
    +/*
    + * Getting to provable safe in place decompression is hard.
    + * Worst case behaviours need to be analized.
    + * Background information:
    + *
    + * The file layout is:
    + * magic[2]
    + * method[1]
    + * flags[1]
    + * timestamp[4]
    + * extraflags[1]
    + * os[1]
    + * compressed data blocks[N]
    + * crc[4] orig_len[4]
    + *
    + * resulting in 18 bytes of non compressed data overhead.
    + *
    + * Files divided into blocks
    + * 1 bit (last block flag)
    + * 2 bits (block type)
    + *
    + * 1 block occurs every 32K -1 bytes or when there 50% compression has been achieved.
    + * The smallest block type encoding is always used.
    + *
    + * stored:
    + * 32 bits length in bytes.
    + *
    + * fixed:
    + * magic fixed tree.
    + * symbols.
    + *
    + * dynamic:
    + * dynamic tree encoding.
    + * symbols.
    + *
    + *
    + * The buffer for decompression in place is the length of the
    + * uncompressed data, plus a small amount extra to keep the algorithm safe.
    + * The compressed data is placed at the end of the buffer. The output
    + * pointer is placed at the start of the buffer and the input pointer
    + * is placed where the compressed data starts. Problems will occur
    + * when the output pointer overruns the input pointer.
    + *
    + * The output pointer can only overrun the input pointer if the input
    + * pointer is moving faster than the output pointer. A condition only
    + * triggered by data whose compressed form is larger than the uncompressed
    + * form.
    + *
    + * The worst case at the block level is a growth of the compressed data
    + * of 5 bytes per 32767 bytes.
    + *
    + * The worst case internal to a compressed block is very hard to figure.
    + * The worst case can at least be boundined by having one bit that represents
    + * 32764 bytes and then all of the rest of the bytes representing the very
    + * very last byte.
    + *
    + * All of which is enough to compute an amount of extra data that is required
    + * to be safe. To avoid problems at the block level allocating 5 extra bytes
    + * per 32767 bytes of data is sufficient. To avoind problems internal to a block
    + * adding an extra 32767 bytes (the worst case uncompressed block size) is
    + * sufficient, to ensure that in the worst case the decompressed data for
    + * block will stop the byte before the compressed data for a block begins.
    + * To avoid problems with the compressed data's meta information an extra 18
    + * bytes are needed. Leading to the formula:
    + *
    + * extra_bytes = (uncompressed_size >> 12) + 32768 + 18 + decompressor_size.
    + *
    + * Adding 8 bytes per 32K is a bit excessive but much easier to calculate.
    + * Adding 32768 instead of 32767 just makes for round numbers.
    + * Adding the decompressor_size is necessary as it musht live after all
    + * of the data as well. Last I measured the decompressor is about 14K.
    + * 10K of actuall data and 4K of bss.
    + *
    + */

    /*
    * gzip declarations
    @@ -30,15 +112,20 @@ typedef unsigned char uch;
    typedef unsigned short ush;
    typedef unsigned long ulg;

    -#define WSIZE 0x8000 /* Window size must be at least 32k, */
    - /* and a power of two */
    -
    -static uch *inbuf; /* input buffer */
    -static uch window[WSIZE]; /* Sliding window buffer */
    -
    -static unsigned insize = 0; /* valid bytes in inbuf */
    -static unsigned inptr = 0; /* index of next byte to be processed in inbuf */
    -static unsigned outcnt = 0; /* bytes in output buffer */
    +#define WSIZE 0x80000000 /* Window size must be at least 32k,
    + * and a power of two
    + * We don't actually have a window just
    + * a huge output buffer so I report
    + * a 2G windows size, as that should
    + * always be larger than our output buffer.
    + */
    +
    +static uch *inbuf; /* input buffer */
    +static uch *window; /* Sliding window buffer, (and final output buffer) */
    +
    +static unsigned insize; /* valid bytes in inbuf */
    +static unsigned inptr; /* index of next byte to be processed in inbuf */
    +static unsigned outcnt; /* bytes in output buffer */

    /* gzip flag byte */
    #define ASCII_FLAG 0x01 /* bit 0 set: file probably ASCII text */
    @@ -89,8 +176,6 @@ extern unsigned char input_data[];
    extern int input_len;

    static long bytes_out = 0;
    -static uch *output_data;
    -static unsigned long output_ptr = 0;

    static void *malloc(int size);
    static void free(void *where);
    @@ -100,17 +185,10 @@ static void *memcpy(void *dest, const vo

    static void putstr(const char *);

    -extern int end;
    -static long free_mem_ptr = (long)&end;
    -static long free_mem_end_ptr;
    -
    -#define INPLACE_MOVE_ROUTINE 0x1000
    -#define LOW_BUFFER_START 0x2000
    -#define LOW_BUFFER_MAX 0x90000
    +static unsigned long free_mem_ptr;
    +static unsigned long free_mem_end_ptr;
    +
    #define HEAP_SIZE 0x3000
    -static unsigned int low_buffer_end, low_buffer_size;
    -static int high_loaded =0;
    -static uch *high_buffer_start /* = (uch *)(((ulg)&end) + HEAP_SIZE)*/;

    static char *vidmem = (char *)0xb8000;
    static int vidport;
    @@ -151,7 +229,7 @@ static void gzip_mark(void **ptr)

    static void gzip_release(void **ptr)
    {
    - free_mem_ptr = (long) *ptr;
    + free_mem_ptr = (unsigned long) *ptr;
    }

    static void scroll(void)
    @@ -179,7 +257,7 @@ static void putstr(const char *s)
    y--;
    }
    } else {
    - vidmem [ ( x + cols * y ) * 2 ] = c;
    + vidmem [ ( x + cols * y ) * 2 ] = c;
    if ( ++x >= cols ) {
    x = 0;
    if ( ++y >= lines ) {
    @@ -224,58 +302,31 @@ static void* memcpy(void* dest, const vo
    */
    static int fill_inbuf(void)
    {
    - if (insize != 0) {
    - error("ran out of input data");
    - }
    -
    - inbuf = input_data;
    - insize = input_len;
    - inptr = 1;
    - return inbuf[0];
    + error("ran out of input data");
    + return 0;
    }

    /* ===========================================================================
    * Write the output window window[0..outcnt-1] and update crc and bytes_out.
    * (Used for the decompressed data only.)
    */
    -static void flush_window_low(void)
    -{
    - ulg c = crc; /* temporary variable */
    - unsigned n;
    - uch *in, *out, ch;
    -
    - in = window;
    - out = &output_data[output_ptr];
    - for (n = 0; n < outcnt; n++) {
    - ch = *out++ = *in++;
    - c = crc_32_tab[((int)c ^ ch) & 0xff] ^ (c >> 8);
    - }
    - crc = c;
    - bytes_out += (ulg)outcnt;
    - output_ptr += (ulg)outcnt;
    - outcnt = 0;
    -}
    -
    -static void flush_window_high(void)
    -{
    - ulg c = crc; /* temporary variable */
    - unsigned n;
    - uch *in, ch;
    - in = window;
    - for (n = 0; n < outcnt; n++) {
    - ch = *output_data++ = *in++;
    - if ((ulg)output_data == low_buffer_end) output_data=high_buffer_start;
    - c = crc_32_tab[((int)c ^ ch) & 0xff] ^ (c >> 8);
    - }
    - crc = c;
    - bytes_out += (ulg)outcnt;
    - outcnt = 0;
    -}
    -
    static void flush_window(void)
    {
    - if (high_loaded) flush_window_high();
    - else flush_window_low();
    + /* With my window equal to my output buffer
    + * I only need to compute the crc here.
    + */
    + ulg c = crc; /* temporary variable */
    + unsigned n;
    + uch *in, ch;
    +
    + in = window;
    + for (n = 0; n < outcnt; n++) {
    + ch = *in++;
    + c = crc_32_tab[((int)c ^ ch) & 0xff] ^ (c >> 8);
    + }
    + crc = c;
    + bytes_out += (ulg)outcnt;
    + outcnt = 0;
    }

    static void error(char *x)
    @@ -287,66 +338,8 @@ static void error(char *x)
    while(1); /* Halt */
    }

    -#define STACK_SIZE (4096)
    -
    -long user_stack [STACK_SIZE];
    -
    -struct {
    - long * a;
    - short b;
    - } stack_start = { & user_stack [STACK_SIZE] , __BOOT_DS };
    -
    -static void setup_normal_output_buffer(void)
    -{
    -#ifdef STANDARD_MEMORY_BIOS_CALL
    - if (RM_EXT_MEM_K < 1024) error("Less than 2MB of memory");
    -#else
    - if ((RM_ALT_MEM_K > RM_EXT_MEM_K ? RM_ALT_MEM_K : RM_EXT_MEM_K) < 1024) error("Less than 2MB of memory");
    -#endif
    - output_data = (unsigned char *)CONFIG_PHYSICAL_START; /* Normally Points to 1M */
    - free_mem_end_ptr = (long)real_mode;
    -}
    -
    -struct moveparams {
    - uch *low_buffer_start; int lcount;
    - uch *high_buffer_start; int hcount;
    -};
    -
    -static void setup_output_buffer_if_we_run_high(struct moveparams *mv)
    -{
    - high_buffer_start = (uch *)(((ulg)&end) + HEAP_SIZE);
    -#ifdef STANDARD_MEMORY_BIOS_CALL
    - if (RM_EXT_MEM_K < (3*1024)) error("Less than 4MB of memory");
    -#else
    - if ((RM_ALT_MEM_K > RM_EXT_MEM_K ? RM_ALT_MEM_K : RM_EXT_MEM_K) < (3*1024)) error("Less than 4MB of memory");
    -#endif
    - mv->low_buffer_start = output_data = (unsigned char *)LOW_BUFFER_START;
    - low_buffer_end = ((unsigned int)real_mode > LOW_BUFFER_MAX
    - ? LOW_BUFFER_MAX : (unsigned int)real_mode) & ~0xfff;
    - low_buffer_size = low_buffer_end - LOW_BUFFER_START;
    - high_loaded = 1;
    - free_mem_end_ptr = (long)high_buffer_start;
    - if ( (CONFIG_PHYSICAL_START + low_buffer_size) > ((ulg)high_buffer_start)) {
    - high_buffer_start = (uch *)(CONFIG_PHYSICAL_START + low_buffer_size);
    - mv->hcount = 0; /* say: we need not to move high_buffer */
    - }
    - else mv->hcount = -1;
    - mv->high_buffer_start = high_buffer_start;
    -}
    -
    -static void close_output_buffer_if_we_run_high(struct moveparams *mv)
    -{
    - if (bytes_out > low_buffer_size) {
    - mv->lcount = low_buffer_size;
    - if (mv->hcount)
    - mv->hcount = bytes_out - low_buffer_size;
    - } else {
    - mv->lcount = bytes_out;
    - mv->hcount = 0;
    - }
    -}
    -
    -asmlinkage int decompress_kernel(struct moveparams *mv, void *rmode)
    +asmlinkage void decompress_kernel(void *rmode, unsigned long end,
    + uch *input_data, unsigned long input_len, uch *output)
    {
    real_mode = rmode;

    @@ -361,13 +354,25 @@ asmlinkage int decompress_kernel(struct
    lines = RM_SCREEN_INFO.orig_video_lines;
    cols = RM_SCREEN_INFO.orig_video_cols;

    - if (free_mem_ptr < 0x100000) setup_normal_output_buffer();
    - else setup_output_buffer_if_we_run_high(mv);
    + window = output; /* Output buffer (Normally at 1M) */
    + free_mem_ptr = end; /* Heap */
    + free_mem_end_ptr = end + HEAP_SIZE;
    + inbuf = input_data; /* Input buffer */
    + insize = input_len;
    + inptr = 0;
    +
    + if (((u32)output - CONFIG_PHYSICAL_START) & 0x3fffff)
    + error("Destination address not 4M aligned");
    + if (end > ((-__PAGE_OFFSET-(512 <<20)-1) & 0x7fffffff))
    + error("Destination address too large");
    +#ifndef CONFIG_RELOCATABLE
    + if ((u32)output != CONFIG_PHYSICAL_START)
    + error("Wrong destination address");
    +#endif

    makecrc();
    putstr("Uncompressing Linux... ");
    gunzip();
    putstr("Ok, booting the kernel.\n");
    - if (high_loaded) close_output_buffer_if_we_run_high(mv);
    - return high_loaded;
    + return;
    }
    diff -puN /dev/null arch/i386/boot/compressed/relocs.c
    --- /dev/null 2006-10-02 12:52:59.410341682 -0400
    +++ linux-2.6.18-git17-root/arch/i386/boot/compressed/relocs.c 2006-10-02 14:09:14.000000000 -0400
    @@ -0,0 +1,563 @@
    +#include <stdio.h>
    +#include <stdarg.h>
    +#include <stdlib.h>
    +#include <stdint.h>
    +#include <string.h>
    +#include <errno.h>
    +#include <unistd.h>
    +#include <elf.h>
    +#include <byteswap.h>
    +#define USE_BSD
    +#include <endian.h>
    +
    +#define MAX_SHDRS 100
    +static Elf32_Ehdr ehdr;
    +static Elf32_Shdr shdr[MAX_SHDRS];
    +static Elf32_Sym *symtab[MAX_SHDRS];
    +static Elf32_Rel *reltab[MAX_SHDRS];
    +static char *strtab[MAX_SHDRS];
    +static unsigned long reloc_count, reloc_idx;
    +static unsigned long *relocs;
    +
    +static void die(char *fmt, ...)
    +{
    + va_list ap;
    + va_start(ap, fmt);
    + vfprintf(stderr, fmt, ap);
    + va_end(ap);
    + exit(1);
    +}
    +
    +static const char *sym_type(unsigned type)
    +{
    + static const char *type_name[] = {
    +#define SYM_TYPE(X) [X] = #X
    + SYM_TYPE(STT_NOTYPE),
    + SYM_TYPE(STT_OBJECT),
    + SYM_TYPE(STT_FUNC),
    + SYM_TYPE(STT_SECTION),
    + SYM_TYPE(STT_FILE),
    + SYM_TYPE(STT_COMMON),
    + SYM_TYPE(STT_TLS),
    +#undef SYM_TYPE
    + };
    + const char *name = "unknown sym type name";
    + if (type < sizeof(type_name)/sizeof(type_name[0])) {
    + name = type_name[type];
    + }
    + return name;
    +}
    +
    +static const char *sym_bind(unsigned bind)
    +{
    + static const char *bind_name[] = {
    +#define SYM_BIND(X) [X] = #X
    + SYM_BIND(STB_LOCAL),
    + SYM_BIND(STB_GLOBAL),
    + SYM_BIND(STB_WEAK),
    +#undef SYM_BIND
    + };
    + const char *name = "unknown sym bind name";
    + if (bind < sizeof(bind_name)/sizeof(bind_name[0])) {
    + name = bind_name[bind];
    + }
    + return name;
    +}
    +
    +static const char *sym_visibility(unsigned visibility)
    +{
    + static const char *visibility_name[] = {
    +#define SYM_VISIBILITY(X) [X] = #X
    + SYM_VISIBILITY(STV_DEFAULT),
    + SYM_VISIBILITY(STV_INTERNAL),
    + SYM_VISIBILITY(STV_HIDDEN),
    + SYM_VISIBILITY(STV_PROTECTED),
    +#undef SYM_VISIBILITY
    + };
    + const char *name = "unknown sym visibility name";
    + if (visibility < sizeof(visibility_name)/sizeof(visibility_name[0])) {
    + name = visibility_name[visibility];
    + }
    + return name;
    +}
    +
    +static const char *rel_type(unsigned type)
    +{
    + static const char *type_name[] = {
    +#define REL_TYPE(X) [X] = #X
    + REL_TYPE(R_386_NONE),
    + REL_TYPE(R_386_32),
    + REL_TYPE(R_386_PC32),
    + REL_TYPE(R_386_GOT32),
    + REL_TYPE(R_386_PLT32),
    + REL_TYPE(R_386_COPY),
    + REL_TYPE(R_386_GLOB_DAT),
    + REL_TYPE(R_386_JMP_SLOT),
    + REL_TYPE(R_386_RELATIVE),
    + REL_TYPE(R_386_GOTOFF),
    + REL_TYPE(R_386_GOTPC),
    +#undef REL_TYPE
    + };
    + const char *name = "unknown type rel type name";
    + if (type < sizeof(type_name)/sizeof(type_name[0])) {
    + name = type_name[type];
    + }
    + return name;
    +}
    +
    +static const char *sec_name(unsigned shndx)
    +{
    + const char *sec_strtab;
    + const char *name;
    + sec_strtab = strtab[ehdr.e_shstrndx];
    + name = "<noname>";
    + if (shndx < ehdr.e_shnum) {
    + name = sec_strtab + shdr[shndx].sh_name;
    + }
    + else if (shndx == SHN_ABS) {
    + name = "ABSOLUTE";
    + }
    + else if (shndx == SHN_COMMON) {
    + name = "COMMON";
    + }
    + return name;
    +}
    +
    +static const char *sym_name(const char *sym_strtab, Elf32_Sym *sym)
    +{
    + const char *name;
    + name = "<noname>";
    + if (sym->st_name) {
    + name = sym_strtab + sym->st_name;
    + }
    + else {
    + name = sec_name(shdr[sym->st_shndx].sh_name);
    + }
    + return name;
    +}
    +
    +
    +
    +#if BYTE_ORDER == LITTLE_ENDIAN
    +#define le16_to_cpu(val) (val)
    +#define le32_to_cpu(val) (val)
    +#endif
    +#if BYTE_ORDER == BIG_ENDIAN
    +#define le16_to_cpu(val) bswap_16(val)
    +#define le32_to_cpu(val) bswap_32(val)
    +#endif
    +
    +static uint16_t elf16_to_cpu(uint16_t val)
    +{
    + return le16_to_cpu(val);
    +}
    +
    +static uint32_t elf32_to_cpu(uint32_t val)
    +{
    + return le32_to_cpu(val);
    +}
    +
    +static void read_ehdr(FILE *fp)
    +{
    + if (fread(&ehdr, sizeof(ehdr), 1, fp) != 1) {
    + die("Cannot read ELF header: %s\n",
    + strerror(errno));
    + }
    + if (memcmp(ehdr.e_ident, ELFMAG, 4) != 0) {
    + die("No ELF magic\n");
    + }
    + if (ehdr.e_ident[EI_CLASS] != ELFCLASS32) {
    + die("Not a 32 bit executable\n");
    + }
    + if (ehdr.e_ident[EI_DATA] != ELFDATA2LSB) {
    + die("Not a LSB ELF executable\n");
    + }
    + if (ehdr.e_ident[EI_VERSION] != EV_CURRENT) {
    + die("Unknown ELF version\n");
    + }
    + /* Convert the fields to native endian */
    + ehdr.e_type = elf16_to_cpu(ehdr.e_type);
    + ehdr.e_machine = elf16_to_cpu(ehdr.e_machine);
    + ehdr.e_version = elf32_to_cpu(ehdr.e_version);
    + ehdr.e_entry = elf32_to_cpu(ehdr.e_entry);
    + ehdr.e_phoff = elf32_to_cpu(ehdr.e_phoff);
    + ehdr.e_shoff = elf32_to_cpu(ehdr.e_shoff);
    + ehdr.e_flags = elf32_to_cpu(ehdr.e_flags);
    + ehdr.e_ehsize = elf16_to_cpu(ehdr.e_ehsize);
    + ehdr.e_phentsize = elf16_to_cpu(ehdr.e_phentsize);
    + ehdr.e_phnum = elf16_to_cpu(ehdr.e_phnum);
    + ehdr.e_shentsize = elf16_to_cpu(ehdr.e_shentsize);
    + ehdr.e_shnum = elf16_to_cpu(ehdr.e_shnum);
    + ehdr.e_shstrndx = elf16_to_cpu(ehdr.e_shstrndx);
    +
    + if ((ehdr.e_type != ET_EXEC) && (ehdr.e_type != ET_DYN)) {
    + die("Unsupported ELF header type\n");
    + }
    + if (ehdr.e_machine != EM_386) {
    + die("Not for x86\n");
    + }
    + if (ehdr.e_version != EV_CURRENT) {
    + die("Unknown ELF version\n");
    + }
    + if (ehdr.e_ehsize != sizeof(Elf32_Ehdr)) {
    + die("Bad Elf header size\n");
    + }
    + if (ehdr.e_phentsize != sizeof(Elf32_Phdr)) {
    + die("Bad program header entry\n");
    + }
    + if (ehdr.e_shentsize != sizeof(Elf32_Shdr)) {
    + die("Bad section header entry\n");
    + }
    + if (ehdr.e_shstrndx >= ehdr.e_shnum) {
    + die("String table index out of bounds\n");
    + }
    +}
    +
    +static void read_shdrs(FILE *fp)
    +{
    + int i;
    + if (ehdr.e_shnum > MAX_SHDRS) {
    + die("%d section headers supported: %d\n",
    + ehdr.e_shnum, MAX_SHDRS);
    + }
    + if (fseek(fp, ehdr.e_shoff, SEEK_SET) < 0) {
    + die("Seek to %d failed: %s\n",
    + ehdr.e_shoff, strerror(errno));
    + }
    + if (fread(&shdr, sizeof(shdr[0]), ehdr.e_shnum, fp) != ehdr.e_shnum) {
    + die("Cannot read ELF section headers: %s\n",
    + strerror(errno));
    + }
    + for(i = 0; i < ehdr.e_shnum; i++) {
    + shdr[i].sh_name = elf32_to_cpu(shdr[i].sh_name);
    + shdr[i].sh_type = elf32_to_cpu(shdr[i].sh_type);
    + shdr[i].sh_flags = elf32_to_cpu(shdr[i].sh_flags);
    + shdr[i].sh_addr = elf32_to_cpu(shdr[i].sh_addr);
    + shdr[i].sh_offset = elf32_to_cpu(shdr[i].sh_offset);
    + shdr[i].sh_size = elf32_to_cpu(shdr[i].sh_size);
    + shdr[i].sh_link = elf32_to_cpu(shdr[i].sh_link);
    + shdr[i].sh_info = elf32_to_cpu(shdr[i].sh_info);
    + shdr[i].sh_addralign = elf32_to_cpu(shdr[i].sh_addralign);
    + shdr[i].sh_entsize = elf32_to_cpu(shdr[i].sh_entsize);
    + }
    +
    +}
    +
    +static void read_strtabs(FILE *fp)
    +{
    + int i;
    + for(i = 0; i < ehdr.e_shnum; i++) {
    + if (shdr[i].sh_type != SHT_STRTAB) {
    + continue;
    + }
    + strtab[i] = malloc(shdr[i].sh_size);
    + if (!strtab[i]) {
    + die("malloc of %d bytes for strtab failed\n",
    + shdr[i].sh_size);
    + }
    + if (fseek(fp, shdr[i].sh_offset, SEEK_SET) < 0) {
    + die("Seek to %d failed: %s\n",
    + shdr[i].sh_offset, strerror(errno));
    + }
    + if (fread(strtab[i], 1, shdr[i].sh_size, fp) != shdr[i].sh_size) {
    + die("Cannot read symbol table: %s\n",
    + strerror(errno));
    + }
    + }
    +}
    +
    +static void read_symtabs(FILE *fp)
    +{
    + int i,j;
    + for(i = 0; i < ehdr.e_shnum; i++) {
    + if (shdr[i].sh_type != SHT_SYMTAB) {
    + continue;
    + }
    + symtab[i] = malloc(shdr[i].sh_size);
    + if (!symtab[i]) {
    + die("malloc of %d bytes for symtab failed\n",
    + shdr[i].sh_size);
    + }
    + if (fseek(fp, shdr[i].sh_offset, SEEK_SET) < 0) {
    + die("Seek to %d failed: %s\n",
    + shdr[i].sh_offset, strerror(errno));
    + }
    + if (fread(symtab[i], 1, shdr[i].sh_size, fp) != shdr[i].sh_size) {
    + die("Cannot read symbol table: %s\n",
    + strerror(errno));
    + }
    + for(j = 0; j < shdr[i].sh_size/sizeof(symtab[i][0]); j++) {
    + symtab[i][j].st_name = elf32_to_cpu(symtab[i][j].st_name);
    + symtab[i][j].st_value = elf32_to_cpu(symtab[i][j].st_value);
    + symtab[i][j].st_size = elf32_to_cpu(symtab[i][j].st_size);
    + symtab[i][j].st_shndx = elf16_to_cpu(symtab[i][j].st_shndx);
    + }
    + }
    +}
    +
    +
    +static void read_relocs(FILE *fp)
    +{
    + int i,j;
    + for(i = 0; i < ehdr.e_shnum; i++) {
    + if (shdr[i].sh_type != SHT_REL) {
    + continue;
    + }
    + reltab[i] = malloc(shdr[i].sh_size);
    + if (!reltab[i]) {
    + die("malloc of %d bytes for relocs failed\n",
    + shdr[i].sh_size);
    + }
    + if (fseek(fp, shdr[i].sh_offset, SEEK_SET) < 0) {
    + die("Seek to %d failed: %s\n",
    + shdr[i].sh_offset, strerror(errno));
    + }
    + if (fread(reltab[i], 1, shdr[i].sh_size, fp) != shdr[i].sh_size) {
    + die("Cannot read symbol table: %s\n",
    + strerror(errno));
    + }
    + for(j = 0; j < shdr[i].sh_size/sizeof(reltab[0][0]); j++) {
    + reltab[i][j].r_offset = elf32_to_cpu(reltab[i][j].r_offset);
    + reltab[i][j].r_info = elf32_to_cpu(reltab[i][j].r_info);
    + }
    + }
    +}
    +
    +
    +static void print_absolute_symbols(void)
    +{
    + int i;
    + printf("Absolute symbols\n");
    + printf(" Num: Value Size Type Bind Visibility Name\n");
    + for(i = 0; i < ehdr.e_shnum; i++) {
    + char *sym_strtab;
    + Elf32_Sym *sh_symtab;
    + int j;
    + if (shdr[i].sh_type != SHT_SYMTAB) {
    + continue;
    + }
    + sh_symtab = symtab[i];
    + sym_strtab = strtab[shdr[i].sh_link];
    + for(j = 0; j < shdr[i].sh_size/sizeof(symtab[0][0]); j++) {
    + Elf32_Sym *sym;
    + const char *name;
    + sym = &symtab[i][j];
    + name = sym_name(sym_strtab, sym);
    + if (sym->st_shndx != SHN_ABS) {
    + continue;
    + }
    + printf("%5d %08x %5d %10s %10s %12s %s\n",
    + j, sym->st_value, sym->st_size,
    + sym_type(ELF32_ST_TYPE(sym->st_info)),
    + sym_bind(ELF32_ST_BIND(sym->st_info)),
    + sym_visibility(ELF32_ST_VISIBILITY(sym->st_other)),
    + name);
    + }
    + }
    + printf("\n");
    +}
    +
    +static void print_absolute_relocs(void)
    +{
    + int i;
    + printf("Absolute relocations\n");
    + printf("Offset Info Type Sym.Value Sym.Name\n");
    + for(i = 0; i < ehdr.e_shnum; i++) {
    + char *sym_strtab;
    + Elf32_Sym *sh_symtab;
    + unsigned sec_applies, sec_symtab;
    + int j;
    + if (shdr[i].sh_type != SHT_REL) {
    + continue;
    + }
    + sec_symtab = shdr[i].sh_link;
    + sec_applies = shdr[i].sh_info;
    + if (!(shdr[sec_applies].sh_flags & SHF_ALLOC)) {
    + continue;
    + }
    + sh_symtab = symtab[sec_symtab];
    + sym_strtab = strtab[shdr[sec_symtab].sh_link];
    + for(j = 0; j < shdr[i].sh_size/sizeof(reltab[0][0]); j++) {
    + Elf32_Rel *rel;
    + Elf32_Sym *sym;
    + const char *name;
    + rel = &reltab[i][j];
    + sym = &sh_symtab[ELF32_R_SYM(rel->r_info)];
    + name = sym_name(sym_strtab, sym);
    + if (sym->st_shndx != SHN_ABS) {
    + continue;
    + }
    + printf("%08x %08x %10s %08x %s\n",
    + rel->r_offset,
    + rel->r_info,
    + rel_type(ELF32_R_TYPE(rel->r_info)),
    + sym->st_value,
    + name);
    + }
    + }
    + printf("\n");
    +}
    +
    +static void walk_relocs(void (*visit)(Elf32_Rel *rel, Elf32_Sym *sym))
    +{
    + int i;
    + /* Walk through the relocations */
    + for(i = 0; i < ehdr.e_shnum; i++) {
    + char *sym_strtab;
    + Elf32_Sym *sh_symtab;
    + unsigned sec_applies, sec_symtab;
    + int j;
    + if (shdr[i].sh_type != SHT_REL) {
    + continue;
    + }
    + sec_symtab = shdr[i].sh_link;
    + sec_applies = shdr[i].sh_info;
    + if (!(shdr[sec_applies].sh_flags & SHF_ALLOC)) {
    + continue;
    + }
    + sh_symtab = symtab[sec_symtab];
    + sym_strtab = strtab[shdr[sec_symtab].sh_link];
    + for(j = 0; j < shdr[i].sh_size/sizeof(reltab[0][0]); j++) {
    + Elf32_Rel *rel;
    + Elf32_Sym *sym;
    + unsigned r_type;
    + rel = &reltab[i][j];
    + sym = &sh_symtab[ELF32_R_SYM(rel->r_info)];
    + r_type = ELF32_R_TYPE(rel->r_info);
    + /* Don't visit relocations to absolute symbols */
    + if (sym->st_shndx == SHN_ABS) {
    + continue;
    + }
    + if (r_type == R_386_PC32) {
    + /* PC relative relocations don't need to be adjusted */
    + }
    + else if (r_type == R_386_32) {
    + /* Visit relocations that need to be adjusted */
    + visit(rel, sym);
    + }
    + else {
    + die("Unsupported relocation type: %d\n", r_type);
    + }
    + }
    + }
    +}
    +
    +static void count_reloc(Elf32_Rel *rel, Elf32_Sym *sym)
    +{
    + reloc_count += 1;
    +}
    +
    +static void collect_reloc(Elf32_Rel *rel, Elf32_Sym *sym)
    +{
    + /* Remember the address that needs to be adjusted. */
    + relocs[reloc_idx++] = rel->r_offset;
    +}
    +
    +static int cmp_relocs(const void *va, const void *vb)
    +{
    + const unsigned long *a, *b;
    + a = va; b = vb;
    + return (*a == *b)? 0 : (*a > *b)? 1 : -1;
    +}
    +
    +static void emit_relocs(int as_text)
    +{
    + int i;
    + /* Count how many relocations I have and allocate space for them. */
    + reloc_count = 0;
    + walk_relocs(count_reloc);
    + relocs = malloc(reloc_count * sizeof(relocs[0]));
    + if (!relocs) {
    + die("malloc of %d entries for relocs failed\n",
    + reloc_count);
    + }
    + /* Collect up the relocations */
    + reloc_idx = 0;
    + walk_relocs(collect_reloc);
    +
    + /* Order the relocations for more efficient processing */
    + qsort(relocs, reloc_count, sizeof(relocs[0]), cmp_relocs);
    +
    + /* Print the relocations */
    + if (as_text) {
    + /* Print the relocations in a form suitable that
    + * gas will like.
    + */
    + printf(".section \".data.reloc\",\"a\"\n");
    + printf(".balign 4\n");
    + for(i = 0; i < reloc_count; i++) {
    + printf("\t .long 0x%08lx\n", relocs[i]);
    + }
    + printf("\n");
    + }
    + else {
    + unsigned char buf[4];
    + buf[0] = buf[1] = buf[2] = buf[3] = 0;
    + /* Print a stop */
    + printf("%c%c%c%c", buf[0], buf[1], buf[2], buf[3]);
    + /* Now print each relocation */
    + for(i = 0; i < reloc_count; i++) {
    + buf[0] = (relocs[i] >> 0) & 0xff;
    + buf[1] = (relocs[i] >> 8) & 0xff;
    + buf[2] = (relocs[i] >> 16) & 0xff;
    + buf[3] = (relocs[i] >> 24) & 0xff;
    + printf("%c%c%c%c", buf[0], buf[1], buf[2], buf[3]);
    + }
    + }
    +}
    +
    +static void usage(void)
    +{
    + die("i386_reloc [--abs | --text] vmlinux\n");
    +}
    +
    +int main(int argc, char **argv)
    +{
    + int show_absolute;
    + int as_text;
    + const char *fname;
    + FILE *fp;
    + int i;
    +
    + show_absolute = 0;
    + as_text = 0;
    + fname = NULL;
    + for(i = 1; i < argc; i++) {
    + char *arg = argv[i];
    + if (*arg == '-') {
    + if (strcmp(argv[1], "--abs") == 0) {
    + show_absolute = 1;
    + continue;
    + }
    + else if (strcmp(argv[1], "--text") == 0) {
    + as_text = 1;
    + continue;
    + }
    + }
    + else if (!fname) {
    + fname = arg;
    + continue;
    + }
    + usage();
    + }
    + if (!fname) {
    + usage();
    + }
    + fp = fopen(fname, "r");
    + if (!fp) {
    + die("Cannot open %s: %s\n",
    + fname, strerror(errno));
    + }
    + read_ehdr(fp);
    + read_shdrs(fp);
    + read_strtabs(fp);
    + read_symtabs(fp);
    + read_relocs(fp);
    + if (show_absolute) {
    + print_absolute_symbols();
    + print_absolute_relocs();
    + return 0;
    + }
    + emit_relocs(as_text);
    + return 0;
    +}
    diff -puN /dev/null arch/i386/boot/compressed/vmlinux.lds
    --- /dev/null 2006-10-02 12:52:59.410341682 -0400
    +++ linux-2.6.18-git17-root/arch/i386/boot/compressed/vmlinux.lds 2006-10-02 14:09:14.000000000 -0400
    @@ -0,0 +1,43 @@
    +OUTPUT_FORMAT("elf32-i386", "elf32-i386", "elf32-i386")
    +OUTPUT_ARCH(i386)
    +ENTRY(startup_32)
    +SECTIONS
    +{
    + /* Be careful parts of head.S assume startup_32 is at
    + * address 0.
    + */
    + . = 0 ;
    + .text.head : {
    + _head = . ;
    + *(.text.head)
    + _ehead = . ;
    + }
    + .data.compressed : {
    + *(.data.compressed)
    + }
    + .text : {
    + _text = .; /* Text */
    + *(.text)
    + *(.text.*)
    + _etext = . ;
    + }
    + .rodata : {
    + _rodata = . ;
    + *(.rodata) /* read-only data */
    + *(.rodata.*)
    + _erodata = . ;
    + }
    + .data : {
    + _data = . ;
    + *(.data)
    + *(.data.*)
    + _edata = . ;
    + }
    + .bss : {
    + _bss = . ;
    + *(.bss)
    + *(.bss.*)
    + *(COMMON)
    + _end = . ;
    + }
    +}
    diff -puN arch/i386/boot/compressed/vmlinux.scr~i386-Relocatable-kernel-support arch/i386/boot/compressed/vmlinux.scr
    --- linux-2.6.18-git17/arch/i386/boot/compressed/vmlinux.scr~i386-Relocatable-kernel-support 2006-10-02 14:09:14.000000000 -0400
    +++ linux-2.6.18-git17-root/arch/i386/boot/compressed/vmlinux.scr 2006-10-02 14:09:14.000000000 -0400
    @@ -1,9 +1,10 @@
    SECTIONS
    {
    - .data : {
    + .data.compressed : {
    input_len = .;
    LONG(input_data_end - input_data) input_data = .;
    *(.data)
    + output_len = . - 4;
    input_data_end = .;
    }
    }
    diff -puN arch/i386/boot/setup.S~i386-Relocatable-kernel-support arch/i386/boot/setup.S
    --- linux-2.6.18-git17/arch/i386/boot/setup.S~i386-Relocatable-kernel-support 2006-10-02 14:09:14.000000000 -0400
    +++ linux-2.6.18-git17-root/arch/i386/boot/setup.S 2006-10-02 14:09:14.000000000 -0400
    @@ -588,11 +588,6 @@ rmodeswtch_normal:
    call default_switch

    rmodeswtch_end:
    -# we get the code32 start address and modify the below 'jmpi'
    -# (loader may have changed it)
    - movl %cs:code32_start, %eax
    - movl %eax, %cs:code32
    -
    # Now we move the system to its rightful place ... but we check if we have a
    # big-kernel. In that case we *must* not move it ...
    testb $LOADED_HIGH, %cs:loadflags
    @@ -788,11 +783,12 @@ a20_err_msg:
    a20_done:

    #endif /* CONFIG_X86_VOYAGER */
    -# set up gdt and idt
    +# set up gdt and idt and 32bit start address
    lidt idt_48 # load idt with 0,0
    xorl %eax, %eax # Compute gdt_base
    movw %ds, %ax # (Convert %ds:gdt to a linear ptr)
    shll $4, %eax
    + addl %eax, code32
    addl $gdt, %eax
    movl %eax, (gdt_48+2)
    lgdt gdt_48 # load gdt with whatever is
    @@ -851,9 +847,26 @@ flush_instr:
    # Manual, Mixing 16-bit and 32-bit code, page 16-6)

    .byte 0x66, 0xea # prefix + jmpi-opcode
    -code32: .long 0x1000 # will be set to 0x100000
    - # for big kernels
    +code32: .long startup_32 # will be set to %cs+startup_32
    .word __BOOT_CS
    +.code32
    +startup_32:
    + movl $(__BOOT_DS), %eax
    + movl %eax, %ds
    + movl %eax, %es
    + movl %eax, %fs
    + movl %eax, %gs
    + movl %eax, %ss
    +
    + xorl %eax, %eax
    +1: incl %eax # check that A20 really IS enabled
    + movl %eax, 0x00000000 # loop forever if it isn't
    + cmpl %eax, 0x00100000
    + je 1b
    +
    + # Jump to the 32bit entry point
    + jmpl *(code32_start - start + (DELTA_INITSEG << 4))(%esi)
    +.code16

    # Here's a bunch of information about your current kernel..
    kernel_version: .ascii UTS_RELEASE
    diff -puN arch/i386/Kconfig~i386-Relocatable-kernel-support arch/i386/Kconfig
    --- linux-2.6.18-git17/arch/i386/Kconfig~i386-Relocatable-kernel-support 2006-10-02 14:09:14.000000000 -0400
    +++ linux-2.6.18-git17-root/arch/i386/Kconfig 2006-10-02 14:33:13.000000000 -0400
    @@ -773,6 +773,18 @@ config CRASH_DUMP
    PHYSICAL_START.
    For more details see Documentation/kdump/kdump.txt

    +config RELOCATABLE
    + bool "Build a relocatable kernel"
    + help
    + This build a kernel image that retains relocation information
    + so it can be loaded someplace besides the default 1MB.
    + The relocations tend to the kernel binary about 10% larger,
    + but are discarded at runtime.
    +
    + One use is for the kexec on panic case where the recovery kernel
    + must live at a different physical address than the primary
    + kernel.
    +
    config PHYSICAL_START
    hex "Physical address where the kernel is loaded" if (EMBEDDED || CRASH_DUMP)

    diff -puN arch/i386/Makefile~i386-Relocatable-kernel-support arch/i386/Makefile
    --- linux-2.6.18-git17/arch/i386/Makefile~i386-Relocatable-kernel-support 2006-10-02 14:09:14.000000000 -0400
    +++ linux-2.6.18-git17-root/arch/i386/Makefile 2006-10-02 14:13:15.000000000 -0400
    @@ -26,7 +26,9 @@ endif

    LDFLAGS := -m elf_i386
    OBJCOPYFLAGS := -O binary -R .note -R .comment -S
    -LDFLAGS_vmlinux :=
    +ifdef CONFIG_RELOCATABLE
    +LDFLAGS_vmlinux := --emit-relocs
    +endif
    CHECKFLAGS += -D__i386__

    CFLAGS += -pipe -msoft-float
    diff -puN include/linux/screen_info.h~i386-Relocatable-kernel-support include/linux/screen_info.h
    --- linux-2.6.18-git17/include/linux/screen_info.h~i386-Relocatable-kernel-support 2006-10-02 14:09:14.000000000 -0400
    +++ linux-2.6.18-git17-root/include/linux/screen_info.h 2006-10-02 14:09:14.000000000 -0400
    @@ -42,7 +42,8 @@ struct screen_info {
    u16 pages; /* 0x32 */
    u16 vesa_attributes; /* 0x34 */
    u32 capabilities; /* 0x36 */
    - /* 0x3a -- 0x3f reserved for future expansion */
    + /* 0x3a -- 0x3b reserved for future expansion */
    + /* 0x3c -- 0x3f micro stack for relocatable kernels */
    };

    extern struct screen_info screen_info;
    _
    -
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