98 lines
2.8 KiB
Plaintext
98 lines
2.8 KiB
Plaintext
Openboot is Sun's implementation of Open Firmware. So we should be able to share
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a lot of code with the PowerPC port. There are some differences however.
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Executable format
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=================
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PowerPC uses COFF. Sparc uses a.out, which is a lot simpler. According to the
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spec, some fields should be zeroed out, but they say implementation may chose
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to allow other values, so a standard a.out file works as well.
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It used to be possible to generate one with objcopy, but support was removed,
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so we now use elf2aout (imported from FreeBSD).
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The file is first loaded at 4000, then relocated to its load address (we use
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202000 and executed there)
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Openfirmware prompt
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===================
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To get the prompt on display, use STOP+A at boot until you get the "ok" prompt.
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On some machines, if no keyboard is detected, the ROM will assume it is set up
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in headless mode, and will expect a BREAK+A on the serial port.
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STOP+N resets all variables to default values (in case you messed up input or
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output, for example).
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Useful commands
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===============
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Disable autoboot to get to the openboot prompt and stop there
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-------------------------------------------------------------
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setenv auto-boot? false
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Configuring for keyboard/framebuffer io
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---------------------------------------
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setenv screen-#columns 160
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setenv screen-#rows 49
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setenv output-device screen:r1920x1080x60
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setenv input-device keyboard
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Configuring openboot for serial port
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------------------------------------
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setenv ttya-mode 38400,8,n,1,-
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setenv output-device ttya
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setenv input-device ttya
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reset
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Boot from network
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-----------------
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static ip:
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This currently works best, because rarp does not let the called binary know the
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IP address. We need the IP address if we want to mount the root filesystem using
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remote_disk server.
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boot net:192.168.1.2,somefile,192.168.1.89
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The first IP is the server from which to download (using TFTP), the second is
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the client IP to use. Once the bootloader starts, it will detect that it is
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booted from network and look for a the remote_disk_server on the same machine.
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rarp:
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This needs a reverse ARP server (easy to setup on any Linux system). You need
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to list the MAC address of the SPARC machine in /etc/ethers on the server. The
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machine will get its IP, and will use TFTP to the server which replied, to get
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the boot file from there.
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boot net:,somefile
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(net is an alias to the network card and also sets the load address: /pci@1f,4000/network@1,1)
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dhcp:
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This needs a DHCP/BOOTP server configured to send the info about where to find
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the file to load and boot.
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boot net:dhcp
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Debugging
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---------
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202000 dis (disassemble starting at 202000 until next return instruction)
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4000 1000 dump (dump 1000 bytes from address 4000)
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.registers (show global registers)
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.locals (show local/windowed registers)
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%pc dis (disassemble code being exectuted)
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ctrace (backtrace)
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