doc/README.qemu_mips

   1
   2 Notes for the Qemu MIPS port
   3
   4 I) Example usage:
   5
   6 # ln -s u-boot.bin mips_bios.bin
   7 start it:
   8 qemu-system-mips -L . /dev/null -nographic
   9
  10 or
  11
  12 if you use a qemu version after commit 4224
  13
  14 create image:
  15 # dd of=flash bs=1k count=4k if=/dev/zero
  16 # dd of=flash bs=1k conv=notrunc if=u-boot.bin
  17 start it:
  18 # qemu-system-mips -M mips -pflash flash -monitor null -nographic
  19
  20 II) How to debug U-Boot
  21
  22 In order to debug U-Boot you need to start qemu with gdb server support (-s)
  23 and waiting the connection to start the CPU (-S)
  24
  25 # qemu-system-mips -S -s -M mips -pflash flash -monitor null -nographic
  26
  27 in an other console you start gdb
  28
  29 1) Debugging of U-Boot Before Relocation
  30
  31 Before relocation, the addresses in the ELF file can be used without any problems
  32 buy connecting to the gdb server localhost:1234
  33
  34 # mipsel-unknown-linux-gnu-gdb u-boot
  35 GNU gdb 6.6
  36 Copyright (C) 2006 Free Software Foundation, Inc.
  37 GDB is free software, covered by the GNU General Public License, and you are
  38 welcome to change it and/or distribute copies of it under certain conditions.
  39 Type "show copying" to see the conditions.
  40 There is absolutely no warranty for GDB.  Type "show warranty" for details.
  41 This GDB was configured as "--host=i486-linux-gnu --target=mipsel-unknown-linux-gnu"...
  42 (gdb)  target remote localhost:1234
  43 Remote debugging using localhost:1234
  44 _start () at start.S:64
  45 64              RVECENT(reset,0)        /* U-boot entry point */
  46 Current language:  auto; currently asm
  47 (gdb)  b board.c:289
  48 Breakpoint 1 at 0xbfc00cc8: file board.c, line 289.
  49 (gdb) c
  50 Continuing.
  51
  52 Breakpoint 1, board_init_f (bootflag=<value optimized out>) at board.c:290
  53 290             relocate_code (addr_sp, id, addr);
  54 Current language:  auto; currently c
  55 (gdb) p/x addr
  56 $1 = 0x87fa0000
  57
  58 2) Debugging of U-Boot After Relocation
  59
  60 For debugging U-Boot after relocation we need to know the address to which
  61 U-Boot relocates itself to 0x87fa0000 by default.
  62 And replace the symbol table to this offset.
  63
  64 (gdb) symbol-file
  65 Discard symbol table from `/private/u-boot-arm/u-boot'? (y or n) y
  66 Error in re-setting breakpoint 1:
  67 No symbol table is loaded.  Use the "file" command.
  68 No symbol file now.
  69 (gdb) add-symbol-file u-boot 0x87fa0000
  70 add symbol table from file "u-boot" at
  71         .text_addr = 0x87fa0000
  72 (y or n) y
  73 Reading symbols from /private/u-boot-arm/u-boot...done.
  74 Breakpoint 1 at 0x87fa0cc8: file board.c, line 289.
  75 (gdb) c
  76 Continuing.
  77
  78 Program received signal SIGINT, Interrupt.
  79 0xffffffff87fa0de4 in udelay (usec=<value optimized out>) at time.c:78
  80 78              while ((tmo - read_c0_count()) < 0x7fffffff)