To make relocation on arm working, the following changes are done: Add new compilerflag: -fPIC -> compiler generates position independent code changes in board code: - 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(). - board.c code is adapted from ppc code - undef CONFIG_RELOC_FIXUP_WORKS -> cmdtabl, and subcommand table must be handled from "hand" collected in section "__datarellocal_start". - How To fixup the sections: __datarel_start, __datarelrolocal_start, __datarellocal_start and __datarelro_start automatically? Then it should be possible to define again CONFIG_RELOC_FIXUP_WORKS - 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 ------------------------------------------------------------------------------------- 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!!! ------------------------------------------------------------------------------------- For boards which boot from nand_spl, it is possible to save a copy if CONFIG_SYS_TEXT_BASE == relocation address! This prevents that uboot code is copied again in relocate_code(). example for the tx25 board: a) cpu starts b) it copies the first page in nand to internal ram (nand_spl_code) c) end executes this code d) this initialize CPU, RAM, ... and copy itself to RAM (this bin must fit in one page, so board_init_f() don;t fit in it ... ) e) there it copy u-boot to CONFIG_SYS_NAND_U_BOOT_DST and starts this image @ CONFIG_SYS_NAND_U_BOOT_START f) u-boot code steps through board_init_f() and calculates the relocation address and copy itself to it If CONFIG_SYS_TEXT_BASE == relocation address, the copying of u-boot in f) could be saved. ------------------------------------------------------------------------------------- ToDo: - fill in bd_t infos (check) - adapt all boards - maybe adapt CONFIG_SYS_TEXT_BASE (this must be checked from board maintainers) This *must* be done for boards, which boot from NOR flash on other boards if CONFIG_SYS_TEXT_BASE = relocation baseaddr, this saves one copying from u-boot code. - 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): - cpu copies the first page from NAND to 0xbb000000 (IMX_NFC_BASE) and start with code execution on this address. - The First page contains u-boot code from u-boot:nand_spl/nand_boot_fsl_nfc.c which inits the dram, cpu registers, reloacte itself to CONFIG_SYS_TEXT_BASE and loads the "real" u-boot to CONFIG_SYS_NAND_U_BOOT_DST and starts execution @CONFIG_SYS_NAND_U_BOOT_START - This u-boot does no ram int, nor cpu register setup. Just looks where it have to relocate and relocate itself to this address. If relocate address = CONFIG_SYS_TEXT_BASE(not the same, as the TEXT_BASE 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 ---------------------------------------- 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 ------------------------------------------------------------------------------------- Debugging u-boot in RAM: (example on the qong board) a) add in config.mk: PLATFORM_CPPFLAGS += -DDEBUG ----------------- b) start debugger arm-linux-gdb u-boot [hs@pollux u-boot]$ arm-linux-gdb u-boot GNU gdb Red Hat Linux (6.7-2rh) Copyright (C) 2007 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. Type "show copying" and "show warranty" for details. This GDB was configured as "--host=i686-pc-linux-gnu --target=arm-linux". The target architecture is set automatically (currently arm) .. (gdb) ----------------- c) connect to target target remote bdi10:2001 (gdb) target remote bdi10:2001 Remote debugging using bdi10:2001 0x8ff17f10 in ?? () (gdb) ----------------- d) discard symbol-file (gdb) symbol-file Discard symbol table from `/home/hs/celf/u-boot/u-boot'? (y or n) y No symbol file now. (gdb) ----------------- e) load new symbol table: (gdb) add-symbol-file u-boot 0x8ff08000 add symbol table from file "u-boot" at .text_addr = 0x8ff08000 (y or n) y Reading symbols from /home/hs/celf/u-boot/u-boot...done. (gdb) c Continuing. ^C Program received signal SIGSTOP, Stopped (signal). 0x8ff17f18 in serial_getc () at serial_mxc.c:192 192 while (__REG(UART_PHYS + UTS) & UTS_RXEMPTY); (gdb) add-symbol-file u-boot 0x8ff08000 ^^^^^^^^^^ get this address from u-boot debug printfs U-Boot 2010.06-rc2-00009-gf77b8b8-dirty (Jun 22 2010 - 09:43:46) U-Boot code: A0000000 -> A0058BAC BSS: -> A0061F10 CPU: Freescale i.MX31 at 398 MHz Board: DAVE/DENX Qong mon: FFFFFFFF gd->monLen: 00061F10 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 391k for U-Boot at: 8ff08000 ^^^^^^^^ Reserving 1280k for malloc() at: 8fdc8000 Reserving 24 Bytes for Board Info at: 8fdc7fe8 Reserving 52 Bytes for Global Data at: 8fdc7fb4 New Stack Pointer is: 8fdc7fb0 RAM Configuration: Bank #0: 80000000 256 MiB relocation Offset is: eff08000 mon: 00058BAC gd->monLen: 00061F10 Now running in RAM - U-Boot at: 8ff08000 ^^^^^^^^ Now you can use gdb as usual :-)