doc/README.arm-relocation - filogic/uboot - Gitiles

 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:

 	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 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 CONFIG_SYS_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 CONFIG_SYS_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 CONFIG_SYS_TEXT_BASE (this must be checked from board maintainers)
   This *must* be done for boards, which boot from NOR flash

   on other boards if CONFIG_SYS_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 CONFIG_SYS_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 init, nor CPU register setup. Just look
   where it has to copy and relocate itself to this address. If
   relocate address = CONFIG_SYS_TEXT_BASE (not the same, as the
   CONFIG_SYS_TEXT_BASE from the nand_spl code), then there is 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 :-)
	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:

	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 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 CONFIG_SYS_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 CONFIG_SYS_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 CONFIG_SYS_TEXT_BASE (this must be checked from board maintainers)
	This must be done for boards, which boot from NOR flash

	on other boards if CONFIG_SYS_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 CONFIG_SYS_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 init, nor CPU register setup. Just look
	where it has to copy and relocate itself to this address. If
	relocate address = CONFIG_SYS_TEXT_BASE (not the same, as the
	CONFIG_SYS_TEXT_BASE from the nand_spl code), then there is 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 :-)