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By Vlad Lungu vlad.lungu@windriver.com 2007-Oct-01
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----------------------------------------
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Qemu is a full system emulator. See
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http://www.nongnu.org/qemu/
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Limitations & comments
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----------------------
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Supports the "-m mips" configuration of qemu: serial,NE2000,IDE.
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Support is big endian only for now (or at least this is what I tested).
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Derived from au1x00 with a lot of things cut out.
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Supports emulated flash (patch Jean-Christophe PLAGNIOL-VILLARD) with
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recent qemu versions. When using emulated flash, launch with
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-pflash <filename> and erase mips_bios.bin.
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Notes for the Qemu MIPS port
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----------------------------
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I) Example usage:
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# ln -s u-boot.bin mips_bios.bin
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start it:
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qemu-system-mips -L . /dev/null -nographic
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or
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if you use a qemu version after commit 4224
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create image:
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# dd of=flash bs=1k count=4k if=/dev/zero
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# dd of=flash bs=1k conv=notrunc if=u-boot.bin
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start it:
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# qemu-system-mips -M mips -pflash flash -monitor null -nographic
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2) Download kernel + initrd
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On ftp://ftp.denx.de/pub/contrib/Jean-Christophe_Plagniol-Villard/qemu_mips/
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you can downland
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#config to build the kernel
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qemu_mips_defconfig
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#patch to fix mips interrupt init on 2.6.24.y kernel
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qemu_mips_kernel.patch
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initrd.gz
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vmlinux
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vmlinux.bin
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System.map
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4) Generate uImage
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# tools/mkimage -A mips -O linux -T kernel -C gzip -a 0x80010000 -e 0x80245650 -n "Linux 2.6.24.y" -d vmlinux.bin.gz uImage
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5) Copy uImage to Flash
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# dd if=uImage bs=1k conv=notrunc seek=224 of=flash
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6) Generate Ide Disk
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# dd of=ide bs=1k cout=100k if=/dev/zero
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# sfdisk -C 261 -d ide
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# partition table of ide
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unit: sectors
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ide1 : start= 63, size= 32067, Id=83
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ide2 : start= 32130, size= 32130, Id=83
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ide3 : start= 64260, size= 4128705, Id=83
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ide4 : start= 0, size= 0, Id= 0
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7) Copy to ide
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# dd if=uImage bs=512 conv=notrunc seek=63 of=ide
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8) Generate ext2 on part 2 on Copy uImage and initrd.gz
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# Attached as loop device ide offset = 32130 * 512
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# losetup -o 16450560 -f ide
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# Format as ext2 ( arg2 : nb blocks)
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# mke2fs /dev/loop0 16065
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# losetup -d /dev/loop0
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# Mount and copy uImage and initrd.gz to it
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# mount -o loop,offset=16450560 -t ext2 ide /mnt
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# mkdir /mnt/boot
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# cp {initrd.gz,uImage} /mnt/boot/
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# Umount it
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# umount /mnt
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9) Set Environment
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setenv rd_start 0x80800000
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setenv rd_size 2663940
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setenv kernel BFC38000
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setenv oad_addr 80500000
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setenv load_addr2 80F00000
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setenv kernel_flash BFC38000
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setenv load_addr_hello 80200000
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setenv bootargs 'root=/dev/ram0 init=/bin/sh'
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setenv load_rd_ext2 'ide res; ext2load ide 0:2 ${rd_start} /boot/initrd.gz'
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setenv load_rd_tftp 'tftp ${rd_start} /initrd.gz'
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setenv load_kernel_hda 'ide res; diskboot ${load_addr} 0:2'
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setenv load_kernel_ext2 'ide res; ext2load ide 0:2 ${load_addr} /boot/uImage'
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setenv load_kernel_tftp 'tftp ${load_addr} /qemu_mips/uImage'
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setenv boot_ext2_ext2 'run load_rd_ext2; run load_kernel_ext2; run addmisc; bootm ${load_addr}'
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setenv boot_ext2_flash 'run load_rd_ext2; run addmisc; bootm ${kernel_flash}'
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setenv boot_ext2_hda 'run load_rd_ext2; run load_kernel_hda; run addmisc; bootm ${load_addr}'
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setenv boot_ext2_tftp 'run load_rd_ext2; run load_kernel_tftp; run addmisc; bootm ${load_addr}'
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setenv boot_tftp_hda 'run load_rd_tftp; run load_kernel_hda; run addmisc; bootm ${load_addr}'
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setenv boot_tftp_ext2 'run load_rd_tftp; run load_kernel_ext2; run addmisc; bootm ${load_addr}'
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setenv boot_tftp_flash 'run load_rd_tftp; run addmisc; bootm ${kernel_flash}'
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setenv boot_tftp_tftp 'run load_rd_tftp; run load_kernel_tftp; run addmisc; bootm ${load_addr}'
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setenv load_hello_tftp 'tftp ${load_addr_hello} /examples/hello_world.bin'
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setenv go_tftp 'run load_hello_tftp; go ${load_addr_hello}'
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setenv addmisc 'setenv bootargs ${bootargs} console=ttyS0,${baudrate} rd_start=${rd_start} rd_size=${rd_size} ethaddr=${ethaddr}'
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setenv bootcmd 'run boot_tftp_flash'
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10) Now you can boot from flash, ide, ide+ext2 and tfp
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# qemu-system-mips -M mips -pflash flash -monitor null -nographic -net nic -net user -tftp `pwd` -hda ide
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II) How to debug U-Boot
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In order to debug U-Boot you need to start qemu with gdb server support (-s)
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and waiting the connection to start the CPU (-S)
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# qemu-system-mips -S -s -M mips -pflash flash -monitor null -nographic -net nic -net user -tftp `pwd` -hda ide
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in an other console you start gdb
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1) Debugging of U-Boot Before Relocation
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Before relocation, the addresses in the ELF file can be used without any problems
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by connecting to the gdb server localhost:1234
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# mipsel-unknown-linux-gnu-gdb u-boot
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GNU gdb 6.6
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Copyright (C) 2006 Free Software Foundation, Inc.
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GDB is free software, covered by the GNU General Public License, and you are
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welcome to change it and/or distribute copies of it under certain conditions.
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Type "show copying" to see the conditions.
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There is absolutely no warranty for GDB. Type "show warranty" for details.
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This GDB was configured as "--host=i486-linux-gnu --target=mipsel-unknown-linux-gnu"...
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(gdb) target remote localhost:1234
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Remote debugging using localhost:1234
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_start () at start.S:64
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64 RVECENT(reset,0) /* U-boot entry point */
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Current language: auto; currently asm
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(gdb) b board.c:289
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Breakpoint 1 at 0xbfc00cc8: file board.c, line 289.
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(gdb) c
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Continuing.
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Breakpoint 1, board_init_f (bootflag=<value optimized out>) at board.c:290
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290 relocate_code (addr_sp, id, addr);
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Current language: auto; currently c
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(gdb) p/x addr
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$1 = 0x87fa0000
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2) Debugging of U-Boot After Relocation
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For debugging U-Boot after relocation we need to know the address to which
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U-Boot relocates itself to 0x87fa0000 by default.
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And replace the symbol table to this offset.
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(gdb) symbol-file
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Discard symbol table from `/private/u-boot-arm/u-boot'? (y or n) y
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Error in re-setting breakpoint 1:
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No symbol table is loaded. Use the "file" command.
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No symbol file now.
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(gdb) add-symbol-file u-boot 0x87fa0000
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add symbol table from file "u-boot" at
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.text_addr = 0x87fa0000
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(y or n) y
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Reading symbols from /private/u-boot-arm/u-boot...done.
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Breakpoint 1 at 0x87fa0cc8: file board.c, line 289.
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(gdb) c
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Continuing.
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Program received signal SIGINT, Interrupt.
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0xffffffff87fa0de4 in udelay (usec=<value optimized out>) at time.c:78
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78 while ((tmo - read_c0_count()) < 0x7fffffff)
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