1To make relocation on arm working, the following changes are done: 2 3At arch level: add linker flag -pie 4 5 This causes the linker to generate fixup tables .rel.dyn and .dynsym, 6 which must be applied to the relocated image before transferring 7 control to it. 8 9 These fixups are described in the ARM ELF documentation as type 23 10 (program-base-relative) and 2 (symbol-relative) 11 12At cpu level: modify linker file and add a relocation and fixup loop 13 14 the linker file must be modified to include the .rel.dyn and .dynsym 15 tables in the binary image, and to provide symbols for the relocation 16 code to access these tables 17 18 The relocation and fixup loop must be executed after executing 19 board_init_f at initial location and before executing board_init_r 20 at final location. 21 22At board level: 23 24 dram_init(): bd pointer is now at this point not accessible, so only 25 detect the real dramsize, and store it in gd->ram_size. Bst detected 26 with get_ram_size(). 27 28TODO: move also dram initialization there on boards where it is possible. 29 30 Setup of the the bd_t dram bank info is done in the new function 31 dram_init_banksize() called after bd is accessible. 32 33At lib level: 34 35 Board.c code is adapted from ppc code 36 37At config level: 38 39 Undefine CONFIG_SYS_ARM_WITHOUT_RELOC 40 41* WARNING ** WARNING ** WARNING ** WARNING ** WARNING ** WARNING ** WARNING * 42 43Boards which are not fixed to support relocation will be REMOVED! 44 45Eventually, CONFIG_SYS_ARM_WITHOUT_RELOC will disappear and boards 46which have to migrated to relocation will disappear too. 47 48----------------------------------------------------------------------------- 49 50For boards which boot from nand_spl, it is possible to save one copy 51if CONFIG_SYS_TEXT_BASE == relocation address! This prevents that uboot code 52is copied again in relocate_code(). 53 54example for the tx25 board: 55 56a) cpu starts 57b) it copies the first page in nand to internal ram 58 (nand_spl_code) 59c) end executes this code 60d) this initialize CPU, RAM, ... and copy itself to RAM 61 (this bin must fit in one page, so board_init_f() 62 don;t fit in it ... ) 63e) there it copy u-boot to CONFIG_SYS_NAND_U_BOOT_DST and 64 starts this image @ CONFIG_SYS_NAND_U_BOOT_START 65f) u-boot code steps through board_init_f() and calculates 66 the relocation address and copy itself to it 67 68If CONFIG_SYS_TEXT_BASE == relocation address, the copying of u-boot 69in f) could be saved. 70 71----------------------------------------------------------------------------- 72 73TODO 74 75- fill in bd_t infos (check) 76- adapt all boards 77 78- maybe adapt CONFIG_SYS_TEXT_BASE (this must be checked from board maintainers) 79 This *must* be done for boards, which boot from NOR flash 80 81 on other boards if CONFIG_SYS_TEXT_BASE = relocation baseaddr, this saves 82 one copying from u-boot code. 83 84- new function dram_init_banksize() is actual board specific. Maybe 85 we make a weak default function in arch/arm/lib/board.c ? 86 87----------------------------------------------------------------------------- 88 89Relocation with NAND_SPL (example for the tx25): 90 91- cpu copies the first page from NAND to 0xbb000000 (IMX_NFC_BASE) 92 and start with code execution on this address. 93 94- The First page contains u-boot code from u-boot:nand_spl/nand_boot_fsl_nfc.c 95 which inits the dram, cpu registers, reloacte itself to CONFIG_SYS_TEXT_BASE and loads 96 the "real" u-boot to CONFIG_SYS_NAND_U_BOOT_DST and starts execution 97 @CONFIG_SYS_NAND_U_BOOT_START 98 99- This u-boot does no RAM init, nor CPU register setup. Just look 100 where it has to copy and relocate itself to this address. If 101 relocate address = CONFIG_SYS_TEXT_BASE (not the same, as the 102 CONFIG_SYS_TEXT_BASE from the nand_spl code), then there is no need 103 to copy, just go on with bss clear and jump to board_init_r. 104 105----------------------------------------------------------------------------- 106 107How ELF relocations 23 and 2 work. 108 109TBC 110 111------------------------------------------------------------------------------------- 112 113Debugging u-boot in RAM: 114(example on the qong board) 115 116a) add in config.mk: 117 118PLATFORM_CPPFLAGS += -DDEBUG 119 120----------------- 121 122b) start debugger 123 124arm-linux-gdb u-boot 125 126[hs@pollux u-boot]$ arm-linux-gdb u-boot 127GNU gdb Red Hat Linux (6.7-2rh) 128Copyright (C) 2007 Free Software Foundation, Inc. 129License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html> 130This is free software: you are free to change and redistribute it. 131There is NO WARRANTY, to the extent permitted by law. Type "show copying" 132and "show warranty" for details. 133This GDB was configured as "--host=i686-pc-linux-gnu --target=arm-linux". 134The target architecture is set automatically (currently arm) 135.. 136(gdb) 137 138----------------- 139 140c) connect to target 141 142target remote bdi10:2001 143 144(gdb) target remote bdi10:2001 145Remote debugging using bdi10:2001 1460x8ff17f10 in ?? () 147(gdb) 148 149----------------- 150 151d) discard symbol-file 152 153(gdb) symbol-file 154Discard symbol table from `/home/hs/celf/u-boot/u-boot'? (y or n) y 155No symbol file now. 156(gdb) 157 158----------------- 159 160e) load new symbol table: 161 162(gdb) add-symbol-file u-boot 0x8ff08000 163add symbol table from file "u-boot" at 164 .text_addr = 0x8ff08000 165(y or n) y 166Reading symbols from /home/hs/celf/u-boot/u-boot...done. 167(gdb) c 168Continuing. 169^C 170Program received signal SIGSTOP, Stopped (signal). 1710x8ff17f18 in serial_getc () at serial_mxc.c:192 172192 while (__REG(UART_PHYS + UTS) & UTS_RXEMPTY); 173(gdb) 174 175add-symbol-file u-boot 0x8ff08000 176 ^^^^^^^^^^ 177 get this address from u-boot debug printfs 178 179U-Boot 2010.06-rc2-00009-gf77b8b8-dirty (Jun 22 2010 - 09:43:46) 180 181U-Boot code: A0000000 -> A0058BAC BSS: -> A0061F10 182CPU: Freescale i.MX31 at 398 MHz 183Board: DAVE/DENX Qong 184mon: FFFFFFFF gd->monLen: 00061F10 185Top of RAM usable for U-Boot at: 90000000 186LCD panel info: 640 x 480, 16 bit/pix 187Reserving 600k for LCD Framebuffer at: 8ff6a000 188Reserving 391k for U-Boot at: 8ff08000 189 ^^^^^^^^ 190Reserving 1280k for malloc() at: 8fdc8000 191Reserving 24 Bytes for Board Info at: 8fdc7fe8 192Reserving 52 Bytes for Global Data at: 8fdc7fb4 193New Stack Pointer is: 8fdc7fb0 194RAM Configuration: 195Bank #0: 80000000 256 MiB 196relocation Offset is: eff08000 197mon: 00058BAC gd->monLen: 00061F10 198Now running in RAM - U-Boot at: 8ff08000 199 ^^^^^^^^ 200 201Now you can use gdb as usual :-) 202