| To make relocation on arm working, the following changes are done: |
| |
| At arch level: add linker flag -pie |
| |
| This causes the linker to generate fixup tables .rel.dyn and .dynsym, |
| which must be applied to the relocated image before transferring |
| control to it. |
| |
| These fixups are described in the ARM ELF documentation as type 23 |
| (program-base-relative) and 2 (symbol-relative) |
| |
| At cpu level: modify linker file and add a relocation and fixup loop |
| |
| the linker file must be modified to include the .rel.dyn and .dynsym |
| tables in the binary image, and to provide symbols for the relocation |
| code to access these tables |
| |
| The relocation and fixup loop must be executed after executing |
| board_init_f at initial location and before executing board_init_r |
| at final location. |
| |
| At board level: |
| |
| dram_init(): bd pointer is now at this point not accessible, so only |
| detect the real dramsize, and store it in gd->ram_size. Bst detected |
| with get_ram_size(). |
| |
| TODO: move also dram initialization there on boards where it is possible. |
| |
| Setup of the the bd_t dram bank info is done in the new function |
| dram_init_banksize() called after bd is accessible. |
| |
| At lib level: |
| |
| Board.c code is adapted from ppc code |
| |
| At config level: |
| |
| Define CONFIG_RELOC_FIXUP_WORKS. |
| Undefine CONFIG_SYS_ARM_WITHOUT_RELOC |
| |
| * WARNING ** WARNING ** WARNING ** WARNING ** WARNING ** WARNING ** WARNING * |
| |
| Boards which are not fixed to support relocation will be REMOVED! |
| |
| Eventually, CONFIG_SYS_ARM_WITHOUT_RELOC and CONFIG_RELOC_FIXUP_WORKS will |
| disappear and boards which have to migrated to relocation will disappear too. |
| |
| ----------------------------------------------------------------------------- |
| |
| For boards which boot from nand_spl, it is possible to save one copy |
| if 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 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 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. |
| |
| ----------------------------------------------------------------------------- |
| |
| How ELF relocations 23 and 2 work. |
| |
| TBC |
| |
| ------------------------------------------------------------------------------------- |
| |
| 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 :-) |