SeaBIOS - Source Code Study (1)

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SeaBIOS handle fw_cfg

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entry_elf -> handle_post() -> dopost() -> maininit() -> interface_init() -> qemu_cfg_init()

ENTRY(entry_elf)

SeaBIOS serial port configuration

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Serial Port Information is listed as follows:

• debug_serial_preinit()
DebugOutputPort = 0x402

Make BIOS Writable

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BDF Architecture is blow:
bus << 16 | device << 11 | function << 8 | offset
But in SeaBIOS:
bus << 8 | dev << 3 | fn
Because when out 0xcf8 port, bdf will be << 8

• foreachbdf(BDF, BUS)
• pci_bus_devfn_to_bdf(bus, devfn)
• pci_next(int bdf, int bus)
• pci_config_readb(u16, bdf, u32 addr)