arm: implement ELF relocations

ELF relocation tables generated with linker option -pie can
be used to fixup code and data in a single loop at relocation,
removing the need for manual fixups anywhere else in the code.

Signed-off-by: Albert Aribaud <albert.aribaud@free.fr>
This commit is contained in:
Albert Aribaud 2010-10-11 13:13:28 +02:00 committed by Wolfgang Denk
parent 89bca0ab69
commit 92d5ecba47
7 changed files with 156 additions and 290 deletions

View file

@ -33,11 +33,6 @@ STANDALONE_LOAD_ADDR = 0xc100000
endif endif
endif endif
ifndef CONFIG_SYS_ARM_WITHOUT_RELOC
# needed for relocation
PLATFORM_RELFLAGS += -fPIC
endif
ifdef CONFIG_SYS_ARM_WITHOUT_RELOC ifdef CONFIG_SYS_ARM_WITHOUT_RELOC
PLATFORM_CPPFLAGS += -DCONFIG_SYS_ARM_WITHOUT_RELOC PLATFORM_CPPFLAGS += -DCONFIG_SYS_ARM_WITHOUT_RELOC
endif endif
@ -72,3 +67,8 @@ PLATFORM_LIBS += $(OBJTREE)/arch/arm/lib/eabi_compat.o
endif endif
endif endif
LDSCRIPT := $(SRCTREE)/$(CPUDIR)/u-boot.lds LDSCRIPT := $(SRCTREE)/$(CPUDIR)/u-boot.lds
ifndef CONFIG_SYS_ARM_WITHOUT_RELOC
# needed for relocation
PLATFORM_LDFLAGS += -pie
endif

View file

@ -10,6 +10,7 @@
* Copyright (c) 2002 Gary Jennejohn <garyj@denx.de> * Copyright (c) 2002 Gary Jennejohn <garyj@denx.de>
* Copyright (c) 2003 Richard Woodruff <r-woodruff2@ti.com> * Copyright (c) 2003 Richard Woodruff <r-woodruff2@ti.com>
* Copyright (c) 2003 Kshitij <kshitij@ti.com> * Copyright (c) 2003 Kshitij <kshitij@ti.com>
* Copyright (c) 2010 Albert Aribaud <albert.aribaud@free.fr>
* *
* See file CREDITS for list of people who contributed to this * See file CREDITS for list of people who contributed to this
* project. * project.
@ -118,22 +119,19 @@ _fiq:
_TEXT_BASE: _TEXT_BASE:
.word TEXT_BASE .word TEXT_BASE
#if defined(CONFIG_SYS_ARM_WITHOUT_RELOC)
.globl _armboot_start
_armboot_start:
.word _start
#endif
/* /*
* These are defined in the board-specific linker script. * These are defined in the board-specific linker script.
* Subtracting _start from them lets the linker put their
* relative position in the executable instead of leaving
* them null.
*/ */
.globl _bss_start .globl _bss_start_ofs
_bss_start: _bss_start_ofs:
.word __bss_start .word __bss_start - _start
.globl _bss_end .globl _bss_end_ofs
_bss_end: _bss_end_ofs:
.word _end .word _end - _start
#ifdef CONFIG_USE_IRQ #ifdef CONFIG_USE_IRQ
/* IRQ stack memory (calculated at run-time) */ /* IRQ stack memory (calculated at run-time) */
@ -153,30 +151,6 @@ FIQ_STACK_START:
IRQ_STACK_START_IN: IRQ_STACK_START_IN:
.word 0x0badc0de .word 0x0badc0de
.globl _datarel_start
_datarel_start:
.word __datarel_start
.globl _datarelrolocal_start
_datarelrolocal_start:
.word __datarelrolocal_start
.globl _datarellocal_start
_datarellocal_start:
.word __datarellocal_start
.globl _datarelro_start
_datarelro_start:
.word __datarelro_start
.globl _got_start
_got_start:
.word __got_start
.globl _got_end
_got_end:
.word __got_end
/* /*
* the actual reset code * the actual reset code
*/ */
@ -226,9 +200,8 @@ stack_setup:
adr r0, _start adr r0, _start
ldr r2, _TEXT_BASE ldr r2, _TEXT_BASE
ldr r3, _bss_start ldr r3, _bss_start_ofs
sub r2, r3, r2 /* r2 <- size of armboot */ add r2, r0, r3 /* r2 <- source end address */
add r2, r0, r2 /* r2 <- source end address */
cmp r0, r6 cmp r0, r6
beq clear_bss beq clear_bss
@ -240,36 +213,54 @@ copy_loop:
blo copy_loop blo copy_loop
#ifndef CONFIG_PRELOADER #ifndef CONFIG_PRELOADER
/* fix got entries */ /*
ldr r1, _TEXT_BASE /* Text base */ * fix .rel.dyn relocations
mov r0, r7 /* reloc addr */ */
ldr r2, _got_start /* addr in Flash */ ldr r0, _TEXT_BASE /* r0 <- Text base */
ldr r3, _got_end /* addr in Flash */ sub r9, r7, r0 /* r9 <- relocation offset */
sub r3, r3, r1 ldr r10, _dynsym_start_ofs /* r10 <- sym table ofs */
add r3, r3, r0 add r10, r10, r0 /* r10 <- sym table in FLASH */
sub r2, r2, r1 ldr r2, _rel_dyn_start_ofs /* r2 <- rel dyn start ofs */
add r2, r2, r0 add r2, r2, r0 /* r2 <- rel dyn start in FLASH */
ldr r3, _rel_dyn_end_ofs /* r3 <- rel dyn end ofs */
add r3, r3, r0 /* r3 <- rel dyn end in FLASH */
fixloop: fixloop:
ldr r4, [r2] ldr r0, [r2] /* r0 <- location to fix up, IN FLASH! */
sub r4, r4, r1 add r0, r9 /* r0 <- location to fix up in RAM */
add r4, r4, r0 ldr r1, [r2, #4]
str r4, [r2] and r8, r1, #0xff
add r2, r2, #4 cmp r8, #23 /* relative fixup? */
beq fixrel
cmp r8, #2 /* absolute fixup? */
beq fixabs
/* ignore unknown type of fixup */
b fixnext
fixabs:
/* absolute fix: set location to (offset) symbol value */
mov r1, r1, LSR #4 /* r1 <- symbol index in .dynsym */
add r1, r10, r1 /* r1 <- address of symbol in table */
ldr r1, [r1, #4] /* r1 <- symbol value */
add r1, r9 /* r1 <- relocated sym addr */
b fixnext
fixrel:
/* relative fix: increase location by offset */
ldr r1, [r0]
add r1, r1, r9
fixnext:
str r1, [r0]
add r2, r2, #8 /* each rel.dyn entry is 8 bytes */
cmp r2, r3 cmp r2, r3
bne fixloop blo fixloop
#endif #endif
#endif /* #ifndef CONFIG_SKIP_RELOCATE_UBOOT */ #endif /* #ifndef CONFIG_SKIP_RELOCATE_UBOOT */
clear_bss: clear_bss:
#ifndef CONFIG_PRELOADER #ifndef CONFIG_PRELOADER
ldr r0, _bss_start ldr r0, _bss_start_ofs
ldr r1, _bss_end ldr r1, _bss_end_ofs
ldr r3, _TEXT_BASE /* Text base */ ldr r3, _TEXT_BASE /* Text base */
mov r4, r7 /* reloc addr */ mov r4, r7 /* reloc addr */
sub r0, r0, r3
add r0, r0, r4 add r0, r0, r4
sub r1, r1, r3
add r1, r1, r4 add r1, r1, r4
mov r2, #0x00000000 /* clear */ mov r2, #0x00000000 /* clear */
@ -287,24 +278,33 @@ clbss_l:str r2, [r0] /* clear loop... */
* initialization, now running from RAM. * initialization, now running from RAM.
*/ */
#ifdef CONFIG_NAND_SPL #ifdef CONFIG_NAND_SPL
ldr pc, _nand_boot ldr r0, _nand_boot_ofs
adr r1, _start
_nand_boot: .word nand_boot add pc, r0, r1
_nand_boot_ofs
: .word nand_boot - _start
#else #else
ldr r0, _TEXT_BASE ldr r0, _board_init_r_ofs
ldr r2, _board_init_r adr r1, _start
sub r2, r2, r0 add r0, r0, r1
add r2, r2, r7 /* position from board_init_r in RAM */ add lr, r0, r9
/* setup parameters for board_init_r */ /* setup parameters for board_init_r */
mov r0, r5 /* gd_t */ mov r0, r5 /* gd_t */
mov r1, r7 /* dest_addr */ mov r1, r7 /* dest_addr */
/* jump to it ... */ /* jump to it ... */
mov lr, r2
mov pc, lr mov pc, lr
_board_init_r: .word board_init_r _board_init_r_ofs:
.word board_init_r - _start
#endif #endif
_rel_dyn_start_ofs:
.word __rel_dyn_start - _start
_rel_dyn_end_ofs:
.word __rel_dyn_end - _start
_dynsym_start_ofs:
.word __dynsym_start - _start
#else /* #if !defined(CONFIG_SYS_ARM_WITHOUT_RELOC) */ #else /* #if !defined(CONFIG_SYS_ARM_WITHOUT_RELOC) */
/* /*
* the actual reset code * the actual reset code
@ -333,10 +333,8 @@ relocate: /* relocate U-Boot to RAM */
ldr r1, _TEXT_BASE /* test if we run from flash or RAM */ ldr r1, _TEXT_BASE /* test if we run from flash or RAM */
cmp r0, r1 /* don't reloc during debug */ cmp r0, r1 /* don't reloc during debug */
beq stack_setup beq stack_setup
ldr r2, _armboot_start ldr r3, _bss_start_ofs /* r3 <- _bss_start - _start */
ldr r3, _bss_start add r2, r0, r3 /* r2 <- source end address */
sub r2, r3, r2 /* r2 <- size of armboot */
add r2, r0, r2 /* r2 <- source end address */
copy_loop: copy_loop:
ldmia r0!, {r3-r10} /* copy from source address [r0] */ ldmia r0!, {r3-r10} /* copy from source address [r0] */
@ -360,8 +358,11 @@ stack_setup:
bic sp, sp, #7 /* 8-byte alignment for ABI compliance */ bic sp, sp, #7 /* 8-byte alignment for ABI compliance */
clear_bss: clear_bss:
ldr r0, _bss_start /* find start of bss segment */ adr r2, _start
ldr r1, _bss_end /* stop here */ ldr r0, _bss_start_ofs /* find start of bss segment */
add r0, r0, r2
ldr r1, _bss_end_ofs /* stop here */
add r1, r1, r2
mov r2, #0x00000000 /* clear */ mov r2, #0x00000000 /* clear */
#ifndef CONFIG_PRELOADER #ifndef CONFIG_PRELOADER
@ -374,13 +375,16 @@ clbss_l:str r2, [r0] /* clear loop... */
bl red_LED_on bl red_LED_on
#endif /* CONFIG_PRELOADER */ #endif /* CONFIG_PRELOADER */
ldr pc, _start_armboot ldr r0, _start_armboot_ofs
adr r1, _start
add r0, r0, r1
ldr pc, r0
_start_armboot: _start_armboot_ofs:
#ifdef CONFIG_NAND_SPL #ifdef CONFIG_NAND_SPL
.word nand_boot .word nand_boot - _start
#else #else
.word start_armboot .word start_armboot - _start
#endif /* CONFIG_NAND_SPL */ #endif /* CONFIG_NAND_SPL */
#endif /* #if !defined(CONFIG_SYS_ARM_WITHOUT_RELOC) */ #endif /* #if !defined(CONFIG_SYS_ARM_WITHOUT_RELOC) */
@ -469,7 +473,7 @@ cpu_init_crit:
sub sp, sp, #S_FRAME_SIZE sub sp, sp, #S_FRAME_SIZE
stmia sp, {r0 - r12} @ Save user registers (now in svc mode) r0-r12 stmia sp, {r0 - r12} @ Save user registers (now in svc mode) r0-r12
#if defined(CONFIG_SYS_ARM_WITHOUT_RELOC) #if defined(CONFIG_SYS_ARM_WITHOUT_RELOC)
ldr r2, _armboot_start adr r2, _start
sub r2, r2, #(CONFIG_STACKSIZE+CONFIG_SYS_MALLOC_LEN) sub r2, r2, #(CONFIG_STACKSIZE+CONFIG_SYS_MALLOC_LEN)
sub r2, r2, #(CONFIG_SYS_GBL_DATA_SIZE+8) @ set base 2 words into abort stack sub r2, r2, #(CONFIG_SYS_GBL_DATA_SIZE+8) @ set base 2 words into abort stack
#else #else
@ -507,7 +511,7 @@ cpu_init_crit:
.macro get_bad_stack .macro get_bad_stack
#if defined(CONFIG_SYS_ARM_WITHOUT_RELOC) #if defined(CONFIG_SYS_ARM_WITHOUT_RELOC)
ldr r13, _armboot_start @ setup our mode stack adr r13, _start @ setup our mode stack
sub r13, r13, #(CONFIG_STACKSIZE+CONFIG_SYS_MALLOC_LEN) sub r13, r13, #(CONFIG_STACKSIZE+CONFIG_SYS_MALLOC_LEN)
sub r13, r13, #(CONFIG_SYS_GBL_DATA_SIZE+8) @ reserved a couple spots in abort stack sub r13, r13, #(CONFIG_SYS_GBL_DATA_SIZE+8) @ reserved a couple spots in abort stack
#else #else

View file

@ -41,21 +41,19 @@ SECTIONS
. = ALIGN(4); . = ALIGN(4);
.data : { .data : {
*(.data) *(.data)
__datarel_start = .;
*(.data.rel)
__datarelrolocal_start = .;
*(.data.rel.ro.local)
__datarellocal_start = .;
*(.data.rel.local)
__datarelro_start = .;
*(.data.rel.ro)
} }
__got_start = .;
. = ALIGN(4); . = ALIGN(4);
.got : { *(.got) }
__got_end = .; __rel_dyn_start = .;
.rel.dyn : { *(.rel.dyn) }
__rel_dyn_end = .;
__dynsym_start = .;
.dynsym : { *(.dynsym) }
. = ALIGN(4);
. = .; . = .;
__u_boot_cmd_start = .; __u_boot_cmd_start = .;
.u_boot_cmd : { *(.u_boot_cmd) } .u_boot_cmd : { *(.u_boot_cmd) }
@ -65,4 +63,10 @@ SECTIONS
__bss_start = .; __bss_start = .;
.bss (NOLOAD) : { *(.bss) . = ALIGN(4); } .bss (NOLOAD) : { *(.bss) . = ALIGN(4); }
_end = .; _end = .;
/DISCARD/ : { *(.dynstr*) }
/DISCARD/ : { *(.dynamic*) }
/DISCARD/ : { *(.plt*) }
/DISCARD/ : { *(.interp*) }
/DISCARD/ : { *(.gnu*) }
} }

View file

@ -21,8 +21,6 @@
#ifndef _ASM_CONFIG_H_ #ifndef _ASM_CONFIG_H_
#define _ASM_CONFIG_H_ #define _ASM_CONFIG_H_
#if defined(CONFIG_SYS_ARM_WITHOUT_RELOC)
/* Relocation to SDRAM works on all ARM boards */ /* Relocation to SDRAM works on all ARM boards */
#define CONFIG_RELOC_FIXUP_WORKS #define CONFIG_RELOC_FIXUP_WORKS
#endif #endif
#endif

View file

@ -30,18 +30,18 @@
#define _U_BOOT_ARM_H_ 1 #define _U_BOOT_ARM_H_ 1
/* for the following variables, see start.S */ /* for the following variables, see start.S */
extern ulong _bss_start; /* code + data end == BSS start */ extern ulong _bss_start_ofs; /* BSS start relative to _start */
extern ulong _bss_end; /* BSS end */ extern ulong _bss_end_ofs; /* BSS end relative to _start */
extern ulong IRQ_STACK_START; /* top of IRQ stack */ extern ulong IRQ_STACK_START; /* top of IRQ stack */
extern ulong FIQ_STACK_START; /* top of FIQ stack */ extern ulong FIQ_STACK_START; /* top of FIQ stack */
#if defined(CONFIG_SYS_ARM_WITHOUT_RELOC) #if defined(CONFIG_SYS_ARM_WITHOUT_RELOC)
extern ulong _armboot_start; /* code start */ extern ulong _armboot_start_ofs; /* code start */
#else #else
extern ulong _TEXT_BASE; /* code start */ extern ulong _TEXT_BASE; /* code start */
extern ulong _datarel_start; extern ulong _datarel_start_ofs;
extern ulong _datarelrolocal_start; extern ulong _datarelrolocal_start_ofs;
extern ulong _datarellocal_start; extern ulong _datarellocal_start_ofs;
extern ulong _datarelro_start; extern ulong _datarelro_start_ofs;
extern ulong IRQ_STACK_START_IN; /* 8 bytes in IRQ stack */ extern ulong IRQ_STACK_START_IN; /* 8 bytes in IRQ stack */
#endif #endif

View file

@ -147,7 +147,7 @@ static int display_banner (void)
#else #else
_armboot_start, _armboot_start,
#endif #endif
_bss_start, _bss_end); _bss_start_ofs+_TEXT_BASE, _bss_end_ofs+_TEXT_BASE);
#ifdef CONFIG_MODEM_SUPPORT #ifdef CONFIG_MODEM_SUPPORT
debug ("Modem Support enabled\n"); debug ("Modem Support enabled\n");
#endif #endif
@ -517,7 +517,7 @@ void board_init_f (ulong bootflag)
memset ((void*)gd, 0, sizeof (gd_t)); memset ((void*)gd, 0, sizeof (gd_t));
gd->mon_len = _bss_end - _TEXT_BASE; gd->mon_len = _bss_end_ofs;
for (init_fnc_ptr = init_sequence; *init_fnc_ptr; ++init_fnc_ptr) { for (init_fnc_ptr = init_sequence; *init_fnc_ptr; ++init_fnc_ptr) {
if ((*init_fnc_ptr)() != 0) { if ((*init_fnc_ptr)() != 0) {
@ -679,6 +679,7 @@ static char *failed = "*** failed ***\n";
* *
************************************************************************ ************************************************************************
*/ */
void board_init_r (gd_t *id, ulong dest_addr) void board_init_r (gd_t *id, ulong dest_addr)
{ {
char *s; char *s;
@ -702,7 +703,7 @@ void board_init_r (gd_t *id, ulong dest_addr)
gd->flags |= GD_FLG_RELOC; /* tell others: relocation done */ gd->flags |= GD_FLG_RELOC; /* tell others: relocation done */
monitor_flash_len = _bss_start - _TEXT_BASE; monitor_flash_len = _bss_start_ofs;
debug ("monitor flash len: %08lX\n", monitor_flash_len); debug ("monitor flash len: %08lX\n", monitor_flash_len);
board_init(); /* Setup chipselects */ board_init(); /* Setup chipselects */
@ -914,6 +915,7 @@ extern void davinci_eth_set_mac_addr (const u_int8_t *addr);
/* NOTREACHED - no way out of command loop except booting */ /* NOTREACHED - no way out of command loop except booting */
} }
#endif /* defined(CONFIG_SYS_ARM_WITHOUT_RELOC) */ #endif /* defined(CONFIG_SYS_ARM_WITHOUT_RELOC) */
void hang (void) void hang (void)

View file

@ -1,49 +1,54 @@
To make relocation on arm working, the following changes are done: To make relocation on arm working, the following changes are done:
Add new compilerflag: At arch level: add linker flag -pie
-fPIC This causes the linker to generate fixup tables .rel.dyn and .dynsym,
which must be applied to the relocated image before transferring
control to it.
-> compiler generates position independent code These fixups are described in the ARM ELF documentation as type 23
(program-base-relative) and 2 (symbol-relative)
changes in board code: At cpu level: modify linker file and add a relocation and fixup loop
- dram_init: the linker file must be modified to include the .rel.dyn and .dynsym
- bd pointer is now at this point not accessible, so only tables in the binary image, and to provide symbols for the relocation
detect the real dramsize, and store it in gd->ram_size. code to access these tables
best detected with get_ram_size();
ToDo: move there also the dram initialization on boards where
it is possible.
- setup the bd_t dram bank info in the new function
dram_init_banksize().
- board.c code is adapted from ppc code The relocation and fixup loop must be executed after executing
board_init_f at initial location and before executing board_init_r
at final location.
- undef CONFIG_RELOC_FIXUP_WORKS At board level:
-> cmdtabl, and subcommand table must be handled from "hand" dram_init(): bd pointer is now at this point not accessible, so only
collected in section "__datarellocal_start". detect the real dramsize, and store it in gd->ram_size. Bst detected
with get_ram_size().
- How To fixup the sections: TODO: move also dram initialization there on boards where it is possible.
__datarel_start, __datarelrolocal_start, __datarellocal_start and Setup of the the bd_t dram bank info is done in the new function
__datarelro_start dram_init_banksize() called after bd is accessible.
automatically? Then it should be possible to define again At lib level:
CONFIG_RELOC_FIXUP_WORKS
- irq stack setup is now not longer on a fix position, instead it is Board.c code is adapted from ppc code
calculated in board_init_f, and stored in gd->irq_sp
------------------------------------------------------------------------------------- At config level:
To compile a board without relocation, define CONFIG_SYS_ARM_WITHOUT_RELOC Define CONFIG_RELOC_FIXUP_WORKS.
This possibility will removed!! So please fix your board to compile without Undefine CONFIG_SYS_ARM_WITHOUT_RELOC
CONFIG_SYS_ARM_WITHOUT_RELOC defined!!!
------------------------------------------------------------------------------------- * WARNING ** WARNING ** WARNING ** WARNING ** WARNING ** WARNING ** WARNING *
For boards which boot from nand_spl, it is possible to save a copy Boards which are not fixed to support relocation will be REMOVED!
Eventually, CONFIG_SYS_ARM_WITHOUT_RELOC and CONFIG_RELOC_FIXUP_WORKS will
disappear and boards which have to migrated to relocation will disappear too.
-----------------------------------------------------------------------------
For boards which boot from nand_spl, it is possible to save one copy
if TEXT_BASE == relocation address! This prevents that uboot code if TEXT_BASE == relocation address! This prevents that uboot code
is copied again in relocate_code(). is copied again in relocate_code().
@ -64,9 +69,9 @@ f) u-boot code steps through board_init_f() and calculates
If TEXT_BASE == relocation address, the copying of u-boot If TEXT_BASE == relocation address, the copying of u-boot
in f) could be saved. in f) could be saved.
------------------------------------------------------------------------------------- -----------------------------------------------------------------------------
ToDo: TODO
- fill in bd_t infos (check) - fill in bd_t infos (check)
- adapt all boards - adapt all boards
@ -80,7 +85,7 @@ ToDo:
- new function dram_init_banksize() is actual board specific. Maybe - new function dram_init_banksize() is actual board specific. Maybe
we make a weak default function in arch/arm/lib/board.c ? we make a weak default function in arch/arm/lib/board.c ?
------------------------------------------------------------------------------------- -----------------------------------------------------------------------------
Relocation with NAND_SPL (example for the tx25): Relocation with NAND_SPL (example for the tx25):
@ -98,158 +103,11 @@ Relocation with NAND_SPL (example for the tx25):
from the nand_spl code), no need to copy, just go on with bss clear from the nand_spl code), no need to copy, just go on with bss clear
and jump to board_init_r. and jump to board_init_r.
------------------------------------------------------------------------------------- -----------------------------------------------------------------------------
Relocation: How ELF relocations 23 and 2 work.
How to translate flash addresses in GOT to ram addresses.
This is automagically done from code, but this example
shows, how this magic code works ;-)
(example on the qong board)
Find a variable: TBC
a) search it in System.map
(for example flash_info)
a005b4c0 B BootpID
a005b4c4 B BootpTry
a005b4c8 b slave
a005b4cc B flash_info
^^^^^^^^
a005c908 b saved_sector.4002
a005c910 b cfi_mtd_info
a005c9c0 b cfi_mtd_names
a005c9d0 B mtd_table
---------------------------------------
b) create hexdump from u-boot code:
hexdump -C u-boot > gnlmpfhex
---------------------------------------
c) search the variables address in the hexdump
*
0005fc80 00 00 00 00 00 00 00 00 2c 06 01 a0 18 cd 05 a0 |........,.......|
0005fc90 9c d4 05 a0 bc b4 05 a0 1c 7f 05 a0 f0 05 01 a0 |................|
0005fca0 08 5a 04 a0 1c ab 05 a0 ec a4 05 a0 98 c3 01 a0 |.Z..............|
0005fcb0 a0 d6 05 a0 04 71 05 a0 c0 f9 00 a0 3c cd 05 a0 |.....q......<...|
0005fcc0 cc b4 05 a0 f0 fa 00 a0 f0 d6 05 a0 10 86 05 a0 |................|
^^^^^^^^^^^
0005fcd0 a4 16 06 a0 dc 64 05 a0 18 86 05 a0 52 48 05 a0 |.....d......RH..|
0005fce0 c0 86 05 a0 24 6e 02 a0 b4 6c 05 a0 b0 94 01 a0 |....$n...l......|
0005fcf0 1c 86 05 a0 50 85 05 a0 d4 0c 06 a0 bc 0b 06 a0 |....P...........|
-> 0005fcc0
----------------------------------------
d) know we calculate this address in RAM
8ff08000 (new address of code in RAM *1)
+ 0005fcc0
- 00008000 (offset of text *2)
----------
8ff5fcc0 -> Addr GOT in RAM
*1:
activate debug and look for the line:
Now running in RAM - U-Boot at: 8ff08000
^^^^^^^^
new address of u-boot code in RAM
*2:
Section Headers:
[Nr] Name Type Addr Off Size ES Flg Lk Inf Al
[ 0] NULL 00000000 000000 000000 00 0 0 0
[ 1] .text PROGBITS a0000000 008000 04599c 00 AX 0 0 32
^^^^^^
Offset of text
----------------------------------------
e) now we look in 8ff5fcc0 (RAM)
QongEVB>md 0x8ff5fcc0
8ff5fcc0 : a005b4cc a000faf0 a005d6f0 a0058610 ................
^^^^^^^^
Bingo, here we have the old flash address (when relocation
is working, here is the fixed ram address. see @ f, how
it gets calculated)
----------------------------------------
f) now translate it in the new RAM address
a005b4cc
- a0000000 TextBase
+ 8ff08000 new address of u-boot in ram
----------
8ff634cc
QongEVB>mm 0x8ff5fcc0 0x8ff634cc 1
QongEVB>md 0x8ff5fcc0
8ff5fcc0 : 8ff634cc a000faf0 a005d6f0 a0058610 .4..............
8ff5fcd0 : a00616a4 a00564dc a0058618 a0054852 .....d......RH..
As this must be done for all address in the GOT, the u-boot
code did this automagically ... :-)
----------------------------------------------
g) check if the new address is really in the bss section:
bss start:
8ff6054c (8ff08000 + 0005854C monitorlen)
bss end:
8ff698ac (8ff08000 + 618AC)
8ff634cc is in bss :-)
----------------------------------------------
h) u-boot prints:
important addresses:
U-Boot code: A0000000 -> A005854C BSS: -> A00618AC TextBase 0xa0000000
Now running in RAM - U-Boot at: 8ff08000 relocBase 0x8ff08000
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U-Boot 2010.06-rc2-00002-gf8fbb25-dirty (Jun 18 2010 - 17:07:19)
U-Boot code: A0000000 -> A005854C BSS: -> A00618AC
CPU: Freescale i.MX31 at 398 MHz
Board: DAVE/DENX Qong
mon: FFFFFFFF gd->monLen: 000618AC
Top of RAM usable for U-Boot at: 90000000
LCD panel info: 640 x 480, 16 bit/pix
Reserving 600k for LCD Framebuffer at: 8ff6a000
Reserving 390k for U-Boot at: 8ff08000
Reserving 1280k for malloc() at: 8fdc8000
Reserving 28 Bytes for Board Info at: 8fdc7fe4
Reserving 48 Bytes for Global Data at: 8fdc7fb4
New Stack Pointer is: 8fdc7fb0
RAM Configuration:
Bank #0: 80000000 256 MiB
mon: 0005854C gd->monLen: 000618AC
Now running in RAM - U-Boot at: 8ff08000
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