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 37* WARNING ** WARNING ** WARNING ** WARNING ** WARNING ** WARNING ** WARNING * 38 39Boards which are not fixed to support relocation will be REMOVED! 40 41----------------------------------------------------------------------------- 42 43For boards which boot from nand_spl, it is possible to save one copy 44if CONFIG_SYS_TEXT_BASE == relocation address! This prevents that uboot code 45is copied again in relocate_code(). 46 47example for the tx25 board: 48 49a) cpu starts 50b) it copies the first page in nand to internal ram 51 (nand_spl_code) 52c) end executes this code 53d) this initialize CPU, RAM, ... and copy itself to RAM 54 (this bin must fit in one page, so board_init_f() 55 don;t fit in it ... ) 56e) there it copy u-boot to CONFIG_SYS_NAND_U_BOOT_DST and 57 starts this image @ CONFIG_SYS_NAND_U_BOOT_START 58f) u-boot code steps through board_init_f() and calculates 59 the relocation address and copy itself to it 60 61If CONFIG_SYS_TEXT_BASE == relocation address, the copying of u-boot 62in f) could be saved. 63 64----------------------------------------------------------------------------- 65 66TODO 67 68- fill in bd_t infos (check) 69- adapt all boards 70 71- maybe adapt CONFIG_SYS_TEXT_BASE (this must be checked from board maintainers) 72 This *must* be done for boards, which boot from NOR flash 73 74 on other boards if CONFIG_SYS_TEXT_BASE = relocation baseaddr, this saves 75 one copying from u-boot code. 76 77- new function dram_init_banksize() is actual board specific. Maybe 78 we make a weak default function in arch/arm/lib/board.c ? 79 80----------------------------------------------------------------------------- 81 82Relocation with NAND_SPL (example for the tx25): 83 84- cpu copies the first page from NAND to 0xbb000000 (IMX_NFC_BASE) 85 and start with code execution on this address. 86 87- The First page contains u-boot code from u-boot:nand_spl/nand_boot_fsl_nfc.c 88 which inits the dram, cpu registers, reloacte itself to CONFIG_SYS_TEXT_BASE and loads 89 the "real" u-boot to CONFIG_SYS_NAND_U_BOOT_DST and starts execution 90 @CONFIG_SYS_NAND_U_BOOT_START 91 92- This u-boot does no RAM init, nor CPU register setup. Just look 93 where it has to copy and relocate itself to this address. If 94 relocate address = CONFIG_SYS_TEXT_BASE (not the same, as the 95 CONFIG_SYS_TEXT_BASE from the nand_spl code), then there is no need 96 to copy, just go on with bss clear and jump to board_init_r. 97 98----------------------------------------------------------------------------- 99 100How ELF relocations 23 and 2 work. 101 102TBC 103 104------------------------------------------------------------------------------------- 105 106Debugging u-boot in RAM: 107(example on the qong board) 108 109a) add in config.mk: 110 111PLATFORM_CPPFLAGS += -DDEBUG 112 113----------------- 114 115b) start debugger 116 117arm-linux-gdb u-boot 118 119[hs@pollux u-boot]$ arm-linux-gdb u-boot 120GNU gdb Red Hat Linux (6.7-2rh) 121Copyright (C) 2007 Free Software Foundation, Inc. 122License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html> 123This is free software: you are free to change and redistribute it. 124There is NO WARRANTY, to the extent permitted by law. Type "show copying" 125and "show warranty" for details. 126This GDB was configured as "--host=i686-pc-linux-gnu --target=arm-linux". 127The target architecture is set automatically (currently arm) 128.. 129(gdb) 130 131----------------- 132 133c) connect to target 134 135target remote bdi10:2001 136 137(gdb) target remote bdi10:2001 138Remote debugging using bdi10:2001 1390x8ff17f10 in ?? () 140(gdb) 141 142----------------- 143 144d) discard symbol-file 145 146(gdb) symbol-file 147Discard symbol table from `/home/hs/celf/u-boot/u-boot'? (y or n) y 148No symbol file now. 149(gdb) 150 151----------------- 152 153e) load new symbol table: 154 155(gdb) add-symbol-file u-boot 0x8ff08000 156add symbol table from file "u-boot" at 157 .text_addr = 0x8ff08000 158(y or n) y 159Reading symbols from /home/hs/celf/u-boot/u-boot...done. 160(gdb) c 161Continuing. 162^C 163Program received signal SIGSTOP, Stopped (signal). 1640x8ff17f18 in serial_getc () at serial_mxc.c:192 165192 while (__REG(UART_PHYS + UTS) & UTS_RXEMPTY); 166(gdb) 167 168add-symbol-file u-boot 0x8ff08000 169 ^^^^^^^^^^ 170 get this address from u-boot debug printfs 171 172U-Boot 2010.06-rc2-00009-gf77b8b8-dirty (Jun 22 2010 - 09:43:46) 173 174U-Boot code: A0000000 -> A0058BAC BSS: -> A0061F10 175CPU: Freescale i.MX31 at 398 MHz 176Board: DAVE/DENX Qong 177mon: FFFFFFFF gd->monLen: 00061F10 178Top of RAM usable for U-Boot at: 90000000 179LCD panel info: 640 x 480, 16 bit/pix 180Reserving 600k for LCD Framebuffer at: 8ff6a000 181Reserving 391k for U-Boot at: 8ff08000 182 ^^^^^^^^ 183Reserving 1280k for malloc() at: 8fdc8000 184Reserving 24 Bytes for Board Info at: 8fdc7fe8 185Reserving 52 Bytes for Global Data at: 8fdc7fb4 186New Stack Pointer is: 8fdc7fb0 187RAM Configuration: 188Bank #0: 80000000 256 MiB 189relocation Offset is: eff08000 190mon: 00058BAC gd->monLen: 00061F10 191Now running in RAM - U-Boot at: 8ff08000 192 ^^^^^^^^ 193 194Now you can use gdb as usual :-) 195