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 Define CONFIG_RELOC_FIXUP_WORKS. 40 Undefine CONFIG_SYS_ARM_WITHOUT_RELOC 41 42* WARNING ** WARNING ** WARNING ** WARNING ** WARNING ** WARNING ** WARNING * 43 44Boards which are not fixed to support relocation will be REMOVED! 45 46Eventually, CONFIG_SYS_ARM_WITHOUT_RELOC and CONFIG_RELOC_FIXUP_WORKS will 47disappear and boards which have to migrated to relocation will disappear too. 48 49----------------------------------------------------------------------------- 50 51For boards which boot from nand_spl, it is possible to save one copy 52if CONFIG_SYS_TEXT_BASE == relocation address! This prevents that uboot code 53is copied again in relocate_code(). 54 55example for the tx25 board: 56 57a) cpu starts 58b) it copies the first page in nand to internal ram 59 (nand_spl_code) 60c) end executes this code 61d) this initialize CPU, RAM, ... and copy itself to RAM 62 (this bin must fit in one page, so board_init_f() 63 don;t fit in it ... ) 64e) there it copy u-boot to CONFIG_SYS_NAND_U_BOOT_DST and 65 starts this image @ CONFIG_SYS_NAND_U_BOOT_START 66f) u-boot code steps through board_init_f() and calculates 67 the relocation address and copy itself to it 68 69If CONFIG_SYS_TEXT_BASE == relocation address, the copying of u-boot 70in f) could be saved. 71 72----------------------------------------------------------------------------- 73 74TODO 75 76- fill in bd_t infos (check) 77- adapt all boards 78 79- maybe adapt CONFIG_SYS_TEXT_BASE (this must be checked from board maintainers) 80 This *must* be done for boards, which boot from NOR flash 81 82 on other boards if CONFIG_SYS_TEXT_BASE = relocation baseaddr, this saves 83 one copying from u-boot code. 84 85- new function dram_init_banksize() is actual board specific. Maybe 86 we make a weak default function in arch/arm/lib/board.c ? 87 88----------------------------------------------------------------------------- 89 90Relocation with NAND_SPL (example for the tx25): 91 92- cpu copies the first page from NAND to 0xbb000000 (IMX_NFC_BASE) 93 and start with code execution on this address. 94 95- The First page contains u-boot code from u-boot:nand_spl/nand_boot_fsl_nfc.c 96 which inits the dram, cpu registers, reloacte itself to CONFIG_SYS_TEXT_BASE and loads 97 the "real" u-boot to CONFIG_SYS_NAND_U_BOOT_DST and starts execution 98 @CONFIG_SYS_NAND_U_BOOT_START 99 100- This u-boot does no RAM init, nor CPU register setup. Just look 101 where it has to copy and relocate itself to this address. If 102 relocate address = CONFIG_SYS_TEXT_BASE (not the same, as the 103 CONFIG_SYS_TEXT_BASE from the nand_spl code), then there is no need 104 to copy, just go on with bss clear and jump to board_init_r. 105 106----------------------------------------------------------------------------- 107 108How ELF relocations 23 and 2 work. 109 110TBC 111 112------------------------------------------------------------------------------------- 113 114Debugging u-boot in RAM: 115(example on the qong board) 116 117a) add in config.mk: 118 119PLATFORM_CPPFLAGS += -DDEBUG 120 121----------------- 122 123b) start debugger 124 125arm-linux-gdb u-boot 126 127[hs@pollux u-boot]$ arm-linux-gdb u-boot 128GNU gdb Red Hat Linux (6.7-2rh) 129Copyright (C) 2007 Free Software Foundation, Inc. 130License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html> 131This is free software: you are free to change and redistribute it. 132There is NO WARRANTY, to the extent permitted by law. Type "show copying" 133and "show warranty" for details. 134This GDB was configured as "--host=i686-pc-linux-gnu --target=arm-linux". 135The target architecture is set automatically (currently arm) 136.. 137(gdb) 138 139----------------- 140 141c) connect to target 142 143target remote bdi10:2001 144 145(gdb) target remote bdi10:2001 146Remote debugging using bdi10:2001 1470x8ff17f10 in ?? () 148(gdb) 149 150----------------- 151 152d) discard symbol-file 153 154(gdb) symbol-file 155Discard symbol table from `/home/hs/celf/u-boot/u-boot'? (y or n) y 156No symbol file now. 157(gdb) 158 159----------------- 160 161e) load new symbol table: 162 163(gdb) add-symbol-file u-boot 0x8ff08000 164add symbol table from file "u-boot" at 165 .text_addr = 0x8ff08000 166(y or n) y 167Reading symbols from /home/hs/celf/u-boot/u-boot...done. 168(gdb) c 169Continuing. 170^C 171Program received signal SIGSTOP, Stopped (signal). 1720x8ff17f18 in serial_getc () at serial_mxc.c:192 173192 while (__REG(UART_PHYS + UTS) & UTS_RXEMPTY); 174(gdb) 175 176add-symbol-file u-boot 0x8ff08000 177 ^^^^^^^^^^ 178 get this address from u-boot debug printfs 179 180U-Boot 2010.06-rc2-00009-gf77b8b8-dirty (Jun 22 2010 - 09:43:46) 181 182U-Boot code: A0000000 -> A0058BAC BSS: -> A0061F10 183CPU: Freescale i.MX31 at 398 MHz 184Board: DAVE/DENX Qong 185mon: FFFFFFFF gd->monLen: 00061F10 186Top of RAM usable for U-Boot at: 90000000 187LCD panel info: 640 x 480, 16 bit/pix 188Reserving 600k for LCD Framebuffer at: 8ff6a000 189Reserving 391k for U-Boot at: 8ff08000 190 ^^^^^^^^ 191Reserving 1280k for malloc() at: 8fdc8000 192Reserving 24 Bytes for Board Info at: 8fdc7fe8 193Reserving 52 Bytes for Global Data at: 8fdc7fb4 194New Stack Pointer is: 8fdc7fb0 195RAM Configuration: 196Bank #0: 80000000 256 MiB 197relocation Offset is: eff08000 198mon: 00058BAC gd->monLen: 00061F10 199Now running in RAM - U-Boot at: 8ff08000 200 ^^^^^^^^ 201 202Now you can use gdb as usual :-) 203