.globl _TEXT_BASE
_TEXT_BASE:
- .word TEXT_BASE
+ .word CONFIG_SYS_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_end
- _bss_end:
- .word _end
-
- #if !defined(CONFIG_SYS_ARM_WITHOUT_RELOC)
- .globl _datarel_start
- _datarel_start:
- .word __datarel_start
+ .globl _bss_start_ofs
+ _bss_start_ofs:
+ .word __bss_start - _start
- .globl _datarelrolocal_start
- _datarelrolocal_start:
- .word __datarelrolocal_start
+ .globl _bss_end_ofs
+ _bss_end_ofs:
+ .word _end - _start
- .globl _datarellocal_start
- _datarellocal_start:
- .word __datarellocal_start
+ .globl _datarel_start_ofs
+ _datarel_start_ofs:
+ .word __datarel_start - _start
- .globl _datarelro_start
- _datarelro_start:
- .word __datarelro_start
+ .globl _datarelrolocal_start_ofs
+ _datarelrolocal_start_ofs:
+ .word __datarelrolocal_start - _start
- .globl _got_start
- _got_start:
- .word __got_start
+ .globl _datarellocal_start_ofs
+ _datarellocal_start_ofs:
+ .word __datarellocal_start - _start
- .globl _got_end
- _got_end:
- .word __got_end
- #endif
+ .globl _datarelro_start_ofs
+ _datarelro_start_ofs:
+ .word __datarelro_start - _start
#ifdef CONFIG_USE_IRQ
/* IRQ stack memory (calculated at run-time) */
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
+if CONFIG_SYS_TEXT_BASE == relocation address! This prevents that uboot code
is copied again in relocate_code().
example for the tx25 board:
f) u-boot code steps through board_init_f() and calculates
the relocation address and copy itself to it
-If TEXT_BASE == relocation address, the copying of u-boot
+If CONFIG_SYS_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
projects / u-boot.git / commitdiff