diff options
Diffstat (limited to 'doc')
| -rw-r--r-- | doc/README.arm-relocation | 222 |
1 files changed, 40 insertions, 182 deletions
diff --git a/doc/README.arm-relocation b/doc/README.arm-relocation index e9fe999..3856633 100644 --- a/doc/README.arm-relocation +++ b/doc/README.arm-relocation @@ -1,49 +1,54 @@ 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 CONFIG_SYS_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 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 @@ -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): CONFIG_SYS_TEXT_BASE from the nand_spl code), then there is 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 :-) - ----------------------------------------------- - -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 - - ---------- - -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 +TBC ------------------------------------------------------------------------------------- |