Signed-off-by: Heiko Schocher hs@denx.de --- doc/README.arm-relocation | 315 +++++++++++++++++++++++++++++++++++++++++++++ 1 files changed, 315 insertions(+), 0 deletions(-) create mode 100644 doc/README.arm-relocation
diff --git a/doc/README.arm-relocation b/doc/README.arm-relocation new file mode 100644 index 0000000..2084de0 --- /dev/null +++ b/doc/README.arm-relocation @@ -0,0 +1,315 @@ +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 + +------------------------------------------------------------------------------------- + +ToDo: + +- fill in bd_t infos (check) +- adapt all boards + +- maybe adapt TEXT_BASE (this must be checked from board maintainers) + This *must* be done for boards, which boot from NOR flash + + on other boards if 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 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 = 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 http://gnu.org/licenses/gpl.html +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 :-)