Commit 92d5ecba authored by Albert Aribaud's avatar Albert Aribaud Committed by Wolfgang Denk
Browse files

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: default avatarAlbert Aribaud <albert.aribaud@free.fr>
parent 89bca0ab
......@@ -33,11 +33,6 @@ STANDALONE_LOAD_ADDR = 0xc100000
endif
endif
ifndef CONFIG_SYS_ARM_WITHOUT_RELOC
# needed for relocation
PLATFORM_RELFLAGS += -fPIC
endif
ifdef CONFIG_SYS_ARM_WITHOUT_RELOC
PLATFORM_CPPFLAGS += -DCONFIG_SYS_ARM_WITHOUT_RELOC
endif
......@@ -72,3 +67,8 @@ PLATFORM_LIBS += $(OBJTREE)/arch/arm/lib/eabi_compat.o
endif
endif
LDSCRIPT := $(SRCTREE)/$(CPUDIR)/u-boot.lds
ifndef CONFIG_SYS_ARM_WITHOUT_RELOC
# needed for relocation
PLATFORM_LDFLAGS += -pie
endif
......@@ -10,6 +10,7 @@
* Copyright (c) 2002 Gary Jennejohn <garyj@denx.de>
* Copyright (c) 2003 Richard Woodruff <r-woodruff2@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
* project.
......@@ -118,22 +119,19 @@ _fiq:
_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.
* Subtracting _start from them lets the linker put their
* relative position in the executable instead of leaving
* them null.
*/
.globl _bss_start
_bss_start:
.word __bss_start
.globl _bss_start_ofs
_bss_start_ofs:
.word __bss_start - _start
.globl _bss_end
_bss_end:
.word _end
.globl _bss_end_ofs
_bss_end_ofs:
.word _end - _start
#ifdef CONFIG_USE_IRQ
/* IRQ stack memory (calculated at run-time) */
......@@ -153,30 +151,6 @@ FIQ_STACK_START:
IRQ_STACK_START_IN:
.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
*/
......@@ -226,9 +200,8 @@ stack_setup:
adr r0, _start
ldr r2, _TEXT_BASE
ldr r3, _bss_start
sub r2, r3, r2 /* r2 <- size of armboot */
add r2, r0, r2 /* r2 <- source end address */
ldr r3, _bss_start_ofs
add r2, r0, r3 /* r2 <- source end address */
cmp r0, r6
beq clear_bss
......@@ -240,36 +213,54 @@ copy_loop:
blo copy_loop
#ifndef CONFIG_PRELOADER
/* fix got entries */
ldr r1, _TEXT_BASE /* Text base */
mov r0, r7 /* reloc addr */
ldr r2, _got_start /* addr in Flash */
ldr r3, _got_end /* addr in Flash */
sub r3, r3, r1
add r3, r3, r0
sub r2, r2, r1
add r2, r2, r0
/*
* fix .rel.dyn relocations
*/
ldr r0, _TEXT_BASE /* r0 <- Text base */
sub r9, r7, r0 /* r9 <- relocation offset */
ldr r10, _dynsym_start_ofs /* r10 <- sym table ofs */
add r10, r10, r0 /* r10 <- sym table in FLASH */
ldr r2, _rel_dyn_start_ofs /* r2 <- rel dyn start ofs */
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:
ldr r4, [r2]
sub r4, r4, r1
add r4, r4, r0
str r4, [r2]
add r2, r2, #4
ldr r0, [r2] /* r0 <- location to fix up, IN FLASH! */
add r0, r9 /* r0 <- location to fix up in RAM */
ldr r1, [r2, #4]
and r8, r1, #0xff
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
bne fixloop
blo fixloop
#endif
#endif /* #ifndef CONFIG_SKIP_RELOCATE_UBOOT */
clear_bss:
#ifndef CONFIG_PRELOADER
ldr r0, _bss_start
ldr r1, _bss_end
ldr r0, _bss_start_ofs
ldr r1, _bss_end_ofs
ldr r3, _TEXT_BASE /* Text base */
mov r4, r7 /* reloc addr */
sub r0, r0, r3
add r0, r0, r4
sub r1, r1, r3
add r1, r1, r4
mov r2, #0x00000000 /* clear */
......@@ -287,24 +278,33 @@ clbss_l:str r2, [r0] /* clear loop... */
* initialization, now running from RAM.
*/
#ifdef CONFIG_NAND_SPL
ldr pc, _nand_boot
_nand_boot: .word nand_boot
ldr r0, _nand_boot_ofs
adr r1, _start
add pc, r0, r1
_nand_boot_ofs
: .word nand_boot - _start
#else
ldr r0, _TEXT_BASE
ldr r2, _board_init_r
sub r2, r2, r0
add r2, r2, r7 /* position from board_init_r in RAM */
ldr r0, _board_init_r_ofs
adr r1, _start
add r0, r0, r1
add lr, r0, r9
/* setup parameters for board_init_r */
mov r0, r5 /* gd_t */
mov r1, r7 /* dest_addr */
/* jump to it ... */
mov lr, r2
mov pc, lr
_board_init_r: .word board_init_r
_board_init_r_ofs:
.word board_init_r - _start
#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) */
/*
* 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 */
cmp r0, r1 /* don't reloc during debug */
beq stack_setup
ldr r2, _armboot_start
ldr r3, _bss_start
sub r2, r3, r2 /* r2 <- size of armboot */
add r2, r0, r2 /* r2 <- source end address */
ldr r3, _bss_start_ofs /* r3 <- _bss_start - _start */
add r2, r0, r3 /* r2 <- source end address */
copy_loop:
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 */
clear_bss:
ldr r0, _bss_start /* find start of bss segment */
ldr r1, _bss_end /* stop here */
adr r2, _start
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 */
#ifndef CONFIG_PRELOADER
......@@ -374,13 +375,16 @@ clbss_l:str r2, [r0] /* clear loop... */
bl red_LED_on
#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
.word nand_boot
.word nand_boot - _start
#else
.word start_armboot
.word start_armboot - _start
#endif /* CONFIG_NAND_SPL */
#endif /* #if !defined(CONFIG_SYS_ARM_WITHOUT_RELOC) */
......@@ -469,7 +473,7 @@ cpu_init_crit:
sub sp, sp, #S_FRAME_SIZE
stmia sp, {r0 - r12} @ Save user registers (now in svc mode) r0-r12
#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_SYS_GBL_DATA_SIZE+8) @ set base 2 words into abort stack
#else
......@@ -507,7 +511,7 @@ cpu_init_crit:
.macro get_bad_stack
#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_SYS_GBL_DATA_SIZE+8) @ reserved a couple spots in abort stack
#else
......
......@@ -41,21 +41,19 @@ SECTIONS
. = ALIGN(4);
.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);
.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 : { *(.u_boot_cmd) }
......@@ -65,4 +63,10 @@ SECTIONS
__bss_start = .;
.bss (NOLOAD) : { *(.bss) . = ALIGN(4); }
_end = .;
/DISCARD/ : { *(.dynstr*) }
/DISCARD/ : { *(.dynamic*) }
/DISCARD/ : { *(.plt*) }
/DISCARD/ : { *(.interp*) }
/DISCARD/ : { *(.gnu*) }
}
......@@ -21,8 +21,6 @@
#ifndef _ASM_CONFIG_H_
#define _ASM_CONFIG_H_
#if defined(CONFIG_SYS_ARM_WITHOUT_RELOC)
/* Relocation to SDRAM works on all ARM boards */
#define CONFIG_RELOC_FIXUP_WORKS
#endif
#endif
......@@ -30,18 +30,18 @@
#define _U_BOOT_ARM_H_ 1
/* for the following variables, see start.S */
extern ulong _bss_start; /* code + data end == BSS start */
extern ulong _bss_end; /* BSS end */
extern ulong _bss_start_ofs; /* BSS start relative to _start */
extern ulong _bss_end_ofs; /* BSS end relative to _start */
extern ulong IRQ_STACK_START; /* top of IRQ stack */
extern ulong FIQ_STACK_START; /* top of FIQ stack */
#if defined(CONFIG_SYS_ARM_WITHOUT_RELOC)
extern ulong _armboot_start; /* code start */
extern ulong _armboot_start_ofs; /* code start */
#else
extern ulong _TEXT_BASE; /* code start */
extern ulong _datarel_start;
extern ulong _datarelrolocal_start;
extern ulong _datarellocal_start;
extern ulong _datarelro_start;
extern ulong _datarel_start_ofs;
extern ulong _datarelrolocal_start_ofs;
extern ulong _datarellocal_start_ofs;
extern ulong _datarelro_start_ofs;
extern ulong IRQ_STACK_START_IN; /* 8 bytes in IRQ stack */
#endif
......
......@@ -147,7 +147,7 @@ static int display_banner (void)
#else
_armboot_start,
#endif
_bss_start, _bss_end);
_bss_start_ofs+_TEXT_BASE, _bss_end_ofs+_TEXT_BASE);
#ifdef CONFIG_MODEM_SUPPORT
debug ("Modem Support enabled\n");
#endif
......@@ -517,7 +517,7 @@ void board_init_f (ulong bootflag)
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) {
if ((*init_fnc_ptr)() != 0) {
......@@ -679,6 +679,7 @@ static char *failed = "*** failed ***\n";
*
************************************************************************
*/
void board_init_r (gd_t *id, ulong dest_addr)
{
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 */
monitor_flash_len = _bss_start - _TEXT_BASE;
monitor_flash_len = _bss_start_ofs;
debug ("monitor flash len: %08lX\n", monitor_flash_len);
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 */
}
#endif /* defined(CONFIG_SYS_ARM_WITHOUT_RELOC) */
void hang (void)
......
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:
- bd pointer is now at this point not accessible, so only
detect the real dramsize, and store it in gd->ram_size.
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().
the linker file must be modified to include the .rel.dyn and .dynsym
tables in the binary image, and to provide symbols for the relocation
code to access these tables
- 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"
collected in section "__datarellocal_start".
dram_init(): bd pointer is now at this point not accessible, so only
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
__datarelro_start
Setup of the the bd_t dram bank info is done in the new function
dram_init_banksize() called after bd is accessible.
automatically? Then it should be possible to define again
CONFIG_RELOC_FIXUP_WORKS
At lib level:
- irq stack setup is now not longer on a fix position, instead it is
calculated in board_init_f, and stored in gd->irq_sp
Board.c code is adapted from ppc code
-------------------------------------------------------------------------------------
At config level:
To compile a board without relocation, define CONFIG_SYS_ARM_WITHOUT_RELOC
This possibility will removed!! So please fix your board to compile without
CONFIG_SYS_ARM_WITHOUT_RELOC defined!!!
Define CONFIG_RELOC_FIXUP_WORKS.
Undefine CONFIG_SYS_ARM_WITHOUT_RELOC
-------------------------------------------------------------------------------------
* WARNING ** WARNING ** WARNING ** WARNING ** WARNING ** WARNING ** WARNING *
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 a copy
For boards which boot from nand_spl, it is possible to save one copy
if TEXT_BASE == relocation address! This prevents that uboot 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
in f) could be saved.
-------------------------------------------------------------------------------------
-----------------------------------------------------------------------------
ToDo:
TODO
- fill in bd_t infos (check)
- adapt all boards
......@@ -80,7 +85,7 @@ ToDo:
- new function dram_init_banksize() is actual board specific. Maybe
we make a weak default function in arch/arm/lib/board.c ?
-------------------------------------------------------------------------------------
-----------------------------------------------------------------------------
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
and jump to board_init_r.
-------------------------------------------------------------------------------------
Relocation:
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:
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
-----------------------------------------------------------------------------
----------------------------------------
How ELF relocations 23 and 2 work.
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 :-)