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Commit | Line | Data |
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1 | To make relocation on arm working, the following changes are done: | |
2 | ||
3 | At 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 | ||
12 | At 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 | ||
22 | At 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 | ||
28 | TODO: 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 | ||
33 | At lib level: | |
34 | ||
35 | Board.c code is adapted from ppc code | |
36 | ||
37 | * WARNING ** WARNING ** WARNING ** WARNING ** WARNING ** WARNING ** WARNING * | |
38 | ||
39 | Boards which are not fixed to support relocation will be REMOVED! | |
40 | ||
41 | ----------------------------------------------------------------------------- | |
42 | ||
43 | For boards which boot from spl, it is possible to save one copy | |
44 | if CONFIG_SYS_TEXT_BASE == relocation address! This prevents that uboot code | |
45 | is copied again in relocate_code(). | |
46 | ||
47 | example for the tx25 board booting from NAND Flash: | |
48 | ||
49 | a) cpu starts | |
50 | b) it copies the first page in nand to internal ram | |
51 | (spl code) | |
52 | c) end executes this code | |
53 | d) 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 ... ) | |
56 | e) there it copy u-boot to CONFIG_SYS_NAND_U_BOOT_DST and | |
57 | starts this image @ CONFIG_SYS_NAND_U_BOOT_START | |
58 | f) u-boot code steps through board_init_f() and calculates | |
59 | the relocation address and copy itself to it | |
60 | ||
61 | If CONFIG_SYS_TEXT_BASE == relocation address, the copying of u-boot | |
62 | in f) could be saved. | |
63 | ||
64 | ----------------------------------------------------------------------------- | |
65 | ||
66 | TODO | |
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 | ||
82 | Relocation with SPL (example for the tx25 booting from NAND Flash): | |
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 drivers/mtd/nand/raw/mxc_nand_spl.c | |
88 | which inits the dram, cpu registers, reloacte itself to CONFIG_SPL_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_SPL_TEXT_BASE from the 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 | ||
100 | How ELF relocations 23 and 2 work. | |
101 | ||
102 | TBC | |
103 | ||
104 | ------------------------------------------------------------------------------------- | |
105 | ||
106 | Debugging u-boot in RAM: | |
107 | (example on the qong board) | |
108 | ||
109 | ----------------- | |
110 | ||
111 | a) start debugger | |
112 | ||
113 | arm-linux-gdb u-boot | |
114 | ||
115 | [hs@pollux u-boot]$ arm-linux-gdb u-boot | |
116 | GNU gdb Red Hat Linux (6.7-2rh) | |
117 | Copyright (C) 2007 Free Software Foundation, Inc. | |
118 | License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html> | |
119 | This is free software: you are free to change and redistribute it. | |
120 | There is NO WARRANTY, to the extent permitted by law. Type "show copying" | |
121 | and "show warranty" for details. | |
122 | This GDB was configured as "--host=i686-pc-linux-gnu --target=arm-linux". | |
123 | The target architecture is set automatically (currently arm) | |
124 | .. | |
125 | (gdb) | |
126 | ||
127 | ----------------- | |
128 | ||
129 | b) connect to target | |
130 | ||
131 | target remote bdi10:2001 | |
132 | ||
133 | (gdb) target remote bdi10:2001 | |
134 | Remote debugging using bdi10:2001 | |
135 | 0x8ff17f10 in ?? () | |
136 | (gdb) | |
137 | ||
138 | ----------------- | |
139 | ||
140 | c) discard symbol-file | |
141 | ||
142 | (gdb) symbol-file | |
143 | Discard symbol table from `/home/hs/celf/u-boot/u-boot'? (y or n) y | |
144 | No symbol file now. | |
145 | (gdb) | |
146 | ||
147 | ----------------- | |
148 | ||
149 | d) load new symbol table: | |
150 | ||
151 | (gdb) add-symbol-file u-boot 0x8ff08000 | |
152 | add symbol table from file "u-boot" at | |
153 | .text_addr = 0x8ff08000 | |
154 | (y or n) y | |
155 | Reading symbols from /home/hs/celf/u-boot/u-boot...done. | |
156 | (gdb) c | |
157 | Continuing. | |
158 | ^C | |
159 | Program received signal SIGSTOP, Stopped (signal). | |
160 | 0x8ff17f18 in serial_getc () at serial_mxc.c:192 | |
161 | 192 while (__REG(UART_PHYS + UTS) & UTS_RXEMPTY); | |
162 | (gdb) | |
163 | ||
164 | add-symbol-file u-boot 0x8ff08000 | |
165 | ^^^^^^^^^^ | |
166 | get this address from u-boot bdinfo command | |
167 | or get it from gd->relocaddr in gdb | |
168 | ||
169 | => bdinfo | |
170 | rch_number = XXXXXXXXXX | |
171 | boot_params = XXXXXXXXXX | |
172 | DRAM bank = XXXXXXXXXX | |
173 | -> start = XXXXXXXXXX | |
174 | -> size = XXXXXXXXXX | |
175 | ethaddr = XXXXXXXXXX | |
176 | ip_addr = XXXXXXXXXX | |
177 | baudrate = XXXXXXXXXX | |
178 | TLB addr = XXXXXXXXXX | |
179 | relocaddr = 0x8ff08000 | |
180 | ^^^^^^^^^^ | |
181 | reloc off = XXXXXXXXXX | |
182 | irq_sp = XXXXXXXXXX | |
183 | sp start = XXXXXXXXXX | |
184 | FB base = XXXXXXXXXX | |
185 | ||
186 | or interrupt execution by any means and re-load the symbols at the location | |
187 | specified by gd->relocaddr -- this is only valid after board_init_f. | |
188 | ||
189 | (gdb) set $s = gd->relocaddr | |
190 | (gdb) symbol-file | |
191 | (gdb) add-symbol-file u-boot $s | |
192 | ||
193 | Now you can use gdb as usual :-) |