[U-Boot] [PATCH RFC] arm920t: implement elf relocation

Andreas Bießmann
2010-10-31T07:25:12Z

Signed-off-by: Andreas Bie?mann <andreas.devel@googlemail.com>
---
This changes give segfault in at least codesourcery 2010q1-202 arm lite toolchain. To test this segfault use:
# make at91rm9200ek_config
# make

arch/arm/cpu/arm920t/start.S | 122 ++++++++++++++++++++-------------------
arch/arm/cpu/arm920t/u-boot.lds | 26 +++++----
2 files changed, 78 insertions(+), 70 deletions(-)

diff --git a/arch/arm/cpu/arm920t/start.S b/arch/arm/cpu/arm920t/start.S
index d4edde7..adaf193 100644
--- a/arch/arm/cpu/arm920t/start.S
+++ b/arch/arm/cpu/arm920t/start.S
@@ -77,14 +77,17 @@ _TEXT_BASE:

/*
* 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) */
@@ -103,30 +106,6 @@ 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 start code
*/
@@ -230,9 +209,8 @@ 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

@@ -243,35 +221,53 @@ 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 offset */
+ add r10, r10, r0 /* r10 <- sym table in FLASH */
+ ldr r2, _rel_dyn_start_ofs /* r2 <- rel dyn start offset */
+ add r2, r2, r0 /* r2 <- rel dyn start in FLASH */
+ ldr r3, _rel_dyn_end_ofs /* r3 <- rel dyn end offset */
+ 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, 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 (offste) 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 address */
+ 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
blo fixloop
#endif

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 */

@@ -289,12 +285,14 @@ 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
+ ldr r2, _board_init_r_ofs
sub r2, r2, r0
add r2, r2, r7 /* position from board_init_r in RAM */
/* setup parameters for board_init_r */
@@ -304,9 +302,17 @@ _nand_boot: .word nand_boot
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
+
/*
*************************************************************************
*
@@ -317,8 +323,6 @@ _board_init_r: .word board_init_r
*
*************************************************************************
*/
-
-
#ifndef CONFIG_SKIP_LOWLEVEL_INIT
cpu_init_crit:
/*
diff --git a/arch/arm/cpu/arm920t/u-boot.lds b/arch/arm/cpu/arm920t/u-boot.lds
index 6985434..2a4ac8f 100644
--- a/arch/arm/cpu/arm920t/u-boot.lds
+++ b/arch/arm/cpu/arm920t/u-boot.lds
@@ -49,21 +49,19 @@ 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) }
@@ -73,4 +71,10 @@ SECTIONS
__bss_start = .;
.bss (NOLOAD) : { *(.bss) . = ALIGN(4); }
_end = .;
+
+ /DISCARD/ : { *(.dynstr*) }
+ /DISCARD/ : { *(.dynamic*) }
+ /DISCARD/ : { *(.plt*) }
+ /DISCARD/ : { *(.interp*) }
+ /DISCARD/ : { *(.gnu*) }
}
--
1.7.3.2