[PATCH 10/12] i386: Relocatable kernel support

Vivek Goyal
2006-10-03T17:33:46Z

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;
_