d29c615f07
This doesn’t change the bootloader bytes themselves (bootloader.img), but helps with debugging in GDB+QEMU.
42 lines
1016 B
Go
42 lines
1016 B
Go
// Package mbr provides a configured version of Sebastian Plotz’s minimal
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// stage1-only Linux bootloader, to be written to a Master Boot Record.
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package mbr
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import (
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"bytes"
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"encoding/binary"
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_ "embed"
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)
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//go:generate make
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//go:embed bootloader.img
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var mbr []byte
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// write to byte offset 433
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type bootloaderParams struct {
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CurrentLBA uint32 // e.g. 8218
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CmdlineLBA uint32 // e.g. 8218
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}
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func Configure(vmlinuzLba, cmdlineLba uint32, partuuid uint32) [446]byte {
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buf := bytes.NewBuffer(make([]byte, 0, 446))
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// buf.Write never fails
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buf.Write(mbr[:432])
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params := bootloaderParams{
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CurrentLBA: vmlinuzLba,
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CmdlineLBA: cmdlineLba,
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}
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binary.Write(buf, binary.LittleEndian, ¶ms)
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if pad := 440 - buf.Len(); pad > 0 {
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buf.Write(bytes.Repeat([]byte{0}, pad))
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}
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// disk signature (for PARTUUID= root device Linux kernel parameter)
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binary.Write(buf, binary.LittleEndian, partuuid)
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binary.Write(buf, binary.LittleEndian, uint16(0x0000))
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var b [446]byte
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copy(b[:], buf.Bytes())
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return b
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}
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