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Heiko Schocherf1d2b312010-09-17 13:10:39 +02001To make relocation on arm working, the following changes are done:
2
3Add new compilerflag:
4
5-fPIC
6
7 -> compiler generates position independent code
8
9changes in board code:
10
11- dram_init:
12 - bd pointer is now at this point not accessible, so only
13 detect the real dramsize, and store it in gd->ram_size.
14 best detected with get_ram_size();
15 ToDo: move there also the dram initialization on boards where
16 it is possible.
17 - setup the bd_t dram bank info in the new function
18 dram_init_banksize().
19
20- board.c code is adapted from ppc code
21
22- undef CONFIG_RELOC_FIXUP_WORKS
23
24 -> cmdtabl, and subcommand table must be handled from "hand"
25 collected in section "__datarellocal_start".
26
27 - How To fixup the sections:
28
29 __datarel_start, __datarelrolocal_start, __datarellocal_start and
30 __datarelro_start
31
32 automatically? Then it should be possible to define again
33 CONFIG_RELOC_FIXUP_WORKS
34
35- irq stack setup is now not longer on a fix position, instead it is
36 calculated in board_init_f, and stored in gd->irq_sp
37
38-------------------------------------------------------------------------------------
39
40To compile a board without relocation, define CONFIG_SYS_ARM_WITHOUT_RELOC
41This possibility will removed!! So please fix your board to compile without
42CONFIG_SYS_ARM_WITHOUT_RELOC defined!!!
43
44-------------------------------------------------------------------------------------
45
Heiko Schocherab86f722010-09-17 13:10:42 +020046For boards which boot from nand_spl, it is possible to save a copy
47if TEXT_BASE == relocation address! This prevents that uboot code
48is copied again in relocate_code().
49
50example for the tx25 board:
51
52a) cpu starts
53b) it copies the first page in nand to internal ram
54 (nand_spl_code)
55c) end executes this code
56d) this initialize CPU, RAM, ... and copy itself to RAM
57 (this bin must fit in one page, so board_init_f()
58 don;t fit in it ... )
59e) there it copy u-boot to CONFIG_SYS_NAND_U_BOOT_DST and
60 starts this image @ CONFIG_SYS_NAND_U_BOOT_START
61f) u-boot code steps through board_init_f() and calculates
62 the relocation address and copy itself to it
63
64If TEXT_BASE == relocation address, the copying of u-boot
65in f) could be saved.
66
67-------------------------------------------------------------------------------------
68
Heiko Schocherf1d2b312010-09-17 13:10:39 +020069ToDo:
70
71- fill in bd_t infos (check)
72- adapt all boards
73
74- maybe adapt TEXT_BASE (this must be checked from board maintainers)
75 This *must* be done for boards, which boot from NOR flash
76
77 on other boards if TEXT_BASE = relocation baseaddr, this saves
78 one copying from u-boot code.
79
80- new function dram_init_banksize() is actual board specific. Maybe
81 we make a weak default function in arch/arm/lib/board.c ?
82
83-------------------------------------------------------------------------------------
84
85Relocation with NAND_SPL (example for the tx25):
86
87- cpu copies the first page from NAND to 0xbb000000 (IMX_NFC_BASE)
88 and start with code execution on this address.
89
90- The First page contains u-boot code from u-boot:nand_spl/nand_boot_fsl_nfc.c
91 which inits the dram, cpu registers, reloacte itself to TEXT_BASE and loads
92 the "real" u-boot to CONFIG_SYS_NAND_U_BOOT_DST and starts execution
93 @CONFIG_SYS_NAND_U_BOOT_START
94
95- This u-boot does no ram int, nor cpu register setup. Just looks
96 where it have to relocate and relocate itself to this address.
97 If relocate address = TEXT_BASE(not the same, as the TEXT_BASE
98 from the nand_spl code), no need to copy, just go on with bss clear
99 and jump to board_init_r.
100
101-------------------------------------------------------------------------------------
102
103Relocation:
104How to translate flash addresses in GOT to ram addresses.
105This is automagically done from code, but this example
106shows, how this magic code works ;-)
107(example on the qong board)
108
109Find a variable:
110
111a) search it in System.map
112(for example flash_info)
113
114a005b4c0 B BootpID
115a005b4c4 B BootpTry
116a005b4c8 b slave
117a005b4cc B flash_info
118^^^^^^^^
119a005c908 b saved_sector.4002
120a005c910 b cfi_mtd_info
121a005c9c0 b cfi_mtd_names
122a005c9d0 B mtd_table
123
124---------------------------------------
125
126b) create hexdump from u-boot code:
127
128hexdump -C u-boot > gnlmpfhex
129
130---------------------------------------
131
132c) search the variables address in the hexdump
133
134
135*
1360005fc80 00 00 00 00 00 00 00 00 2c 06 01 a0 18 cd 05 a0 |........,.......|
1370005fc90 9c d4 05 a0 bc b4 05 a0 1c 7f 05 a0 f0 05 01 a0 |................|
1380005fca0 08 5a 04 a0 1c ab 05 a0 ec a4 05 a0 98 c3 01 a0 |.Z..............|
1390005fcb0 a0 d6 05 a0 04 71 05 a0 c0 f9 00 a0 3c cd 05 a0 |.....q......<...|
1400005fcc0 cc b4 05 a0 f0 fa 00 a0 f0 d6 05 a0 10 86 05 a0 |................|
141 ^^^^^^^^^^^
1420005fcd0 a4 16 06 a0 dc 64 05 a0 18 86 05 a0 52 48 05 a0 |.....d......RH..|
1430005fce0 c0 86 05 a0 24 6e 02 a0 b4 6c 05 a0 b0 94 01 a0 |....$n...l......|
1440005fcf0 1c 86 05 a0 50 85 05 a0 d4 0c 06 a0 bc 0b 06 a0 |....P...........|
145
146
147-> 0005fcc0
148
149----------------------------------------
150
151d) know we calculate this address in RAM
152
153
154 8ff08000 (new address of code in RAM *1)
155
156+ 0005fcc0
157
158- 00008000 (offset of text *2)
159
160----------
161
162 8ff5fcc0 -> Addr GOT in RAM
163
164*1:
165activate debug and look for the line:
166Now running in RAM - U-Boot at: 8ff08000
167 ^^^^^^^^
168 new address of u-boot code in RAM
169
170*2:
171Section Headers:
172 [Nr] Name Type Addr Off Size ES Flg Lk Inf Al
173 [ 0] NULL 00000000 000000 000000 00 0 0 0
174 [ 1] .text PROGBITS a0000000 008000 04599c 00 AX 0 0 32
175 ^^^^^^
176 Offset of text
177
178----------------------------------------
179
180e) now we look in 8ff5fcc0 (RAM)
181
182
183QongEVB>md 0x8ff5fcc0
1848ff5fcc0 : a005b4cc a000faf0 a005d6f0 a0058610 ................
185 ^^^^^^^^
186 Bingo, here we have the old flash address (when relocation
187 is working, here is the fixed ram address. see @ f, how
188 it gets calculated)
189
190
191----------------------------------------
192
193f) now translate it in the new RAM address
194
195 a005b4cc
196
197- a0000000 TextBase
198
199+ 8ff08000 new address of u-boot in ram
200----------
201 8ff634cc
202
203QongEVB>mm 0x8ff5fcc0 0x8ff634cc 1
204QongEVB>md 0x8ff5fcc0
2058ff5fcc0 : 8ff634cc a000faf0 a005d6f0 a0058610 .4..............
2068ff5fcd0 : a00616a4 a00564dc a0058618 a0054852 .....d......RH..
207
208As this must be done for all address in the GOT, the u-boot
209code did this automagically ... :-)
210
211----------------------------------------------
212
213g) check if the new address is really in the bss section:
214
215bss start:
2168ff6054c (8ff08000 + 0005854C monitorlen)
217
218bss end:
2198ff698ac (8ff08000 + 618AC)
220
2218ff634cc is in bss :-)
222
223----------------------------------------------
224
225h) u-boot prints:
226
227important addresses:
228
229U-Boot code: A0000000 -> A005854C BSS: -> A00618AC TextBase 0xa0000000
230Now running in RAM - U-Boot at: 8ff08000 relocBase 0x8ff08000
231
232
233---------
234
235U-Boot 2010.06-rc2-00002-gf8fbb25-dirty (Jun 18 2010 - 17:07:19)
236
237U-Boot code: A0000000 -> A005854C BSS: -> A00618AC
238CPU: Freescale i.MX31 at 398 MHz
239Board: DAVE/DENX Qong
240mon: FFFFFFFF gd->monLen: 000618AC
241Top of RAM usable for U-Boot at: 90000000
242LCD panel info: 640 x 480, 16 bit/pix
243Reserving 600k for LCD Framebuffer at: 8ff6a000
244Reserving 390k for U-Boot at: 8ff08000
245Reserving 1280k for malloc() at: 8fdc8000
246Reserving 28 Bytes for Board Info at: 8fdc7fe4
247Reserving 48 Bytes for Global Data at: 8fdc7fb4
248New Stack Pointer is: 8fdc7fb0
249RAM Configuration:
250Bank #0: 80000000 256 MiB
251mon: 0005854C gd->monLen: 000618AC
252Now running in RAM - U-Boot at: 8ff08000
253
254-------------------------------------------------------------------------------------
255
256Debugging u-boot in RAM:
257(example on the qong board)
258
259a) add in config.mk:
260
261PLATFORM_CPPFLAGS += -DDEBUG
262
263-----------------
264
265b) start debugger
266
267arm-linux-gdb u-boot
268
269[hs@pollux u-boot]$ arm-linux-gdb u-boot
270GNU gdb Red Hat Linux (6.7-2rh)
271Copyright (C) 2007 Free Software Foundation, Inc.
272License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
273This is free software: you are free to change and redistribute it.
274There is NO WARRANTY, to the extent permitted by law. Type "show copying"
275and "show warranty" for details.
276This GDB was configured as "--host=i686-pc-linux-gnu --target=arm-linux".
277The target architecture is set automatically (currently arm)
278..
279(gdb)
280
281-----------------
282
283c) connect to target
284
285target remote bdi10:2001
286
287(gdb) target remote bdi10:2001
288Remote debugging using bdi10:2001
2890x8ff17f10 in ?? ()
290(gdb)
291
292-----------------
293
294d) discard symbol-file
295
296(gdb) symbol-file
297Discard symbol table from `/home/hs/celf/u-boot/u-boot'? (y or n) y
298No symbol file now.
299(gdb)
300
301-----------------
302
303e) load new symbol table:
304
305(gdb) add-symbol-file u-boot 0x8ff08000
306add symbol table from file "u-boot" at
307 .text_addr = 0x8ff08000
308(y or n) y
309Reading symbols from /home/hs/celf/u-boot/u-boot...done.
310(gdb) c
311Continuing.
312^C
313Program received signal SIGSTOP, Stopped (signal).
3140x8ff17f18 in serial_getc () at serial_mxc.c:192
315192 while (__REG(UART_PHYS + UTS) & UTS_RXEMPTY);
316(gdb)
317
318add-symbol-file u-boot 0x8ff08000
319 ^^^^^^^^^^
320 get this address from u-boot debug printfs
321
322U-Boot 2010.06-rc2-00009-gf77b8b8-dirty (Jun 22 2010 - 09:43:46)
323
324U-Boot code: A0000000 -> A0058BAC BSS: -> A0061F10
325CPU: Freescale i.MX31 at 398 MHz
326Board: DAVE/DENX Qong
327mon: FFFFFFFF gd->monLen: 00061F10
328Top of RAM usable for U-Boot at: 90000000
329LCD panel info: 640 x 480, 16 bit/pix
330Reserving 600k for LCD Framebuffer at: 8ff6a000
331Reserving 391k for U-Boot at: 8ff08000
332 ^^^^^^^^
333Reserving 1280k for malloc() at: 8fdc8000
334Reserving 24 Bytes for Board Info at: 8fdc7fe8
335Reserving 52 Bytes for Global Data at: 8fdc7fb4
336New Stack Pointer is: 8fdc7fb0
337RAM Configuration:
338Bank #0: 80000000 256 MiB
339relocation Offset is: eff08000
340mon: 00058BAC gd->monLen: 00061F10
341Now running in RAM - U-Boot at: 8ff08000
342 ^^^^^^^^
343
344Now you can use gdb as usual :-)