Reorganized file structure
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@ -1,66 +0,0 @@
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package elf
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import (
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"encoding/binary"
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"io"
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"git.akyoto.dev/cli/q/src/config"
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)
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// ELF represents an ELF file.
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type ELF struct {
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Header
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ProgramHeader
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Code []byte
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Data []byte
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}
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// New creates a new ELF binary.
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func New(code []byte, data []byte) *ELF {
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elf := &ELF{
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Header: Header{
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Magic: [4]byte{0x7F, 'E', 'L', 'F'},
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Class: 2,
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Endianness: LittleEndian,
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Version: 1,
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OSABI: 0,
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ABIVersion: 0,
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Type: TypeExecutable,
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Architecture: ArchitectureAMD64,
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FileVersion: 1,
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EntryPointInMemory: config.BaseAddress + config.CodeOffset,
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ProgramHeaderOffset: HeaderSize,
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SectionHeaderOffset: 0,
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Flags: 0,
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Size: HeaderSize,
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ProgramHeaderEntrySize: ProgramHeaderSize,
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ProgramHeaderEntryCount: 1,
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SectionHeaderEntrySize: SectionHeaderSize,
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SectionHeaderEntryCount: 0,
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SectionNameStringTableIndex: 0,
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},
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ProgramHeader: ProgramHeader{
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Type: ProgramTypeLOAD,
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Flags: ProgramFlagsExecutable,
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Offset: config.CodeOffset,
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VirtualAddress: config.BaseAddress + config.CodeOffset,
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PhysicalAddress: config.BaseAddress + config.CodeOffset,
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SizeInFile: int64(len(code)),
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SizeInMemory: int64(len(code)),
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Align: config.Align,
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},
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Code: code,
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Data: data,
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}
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return elf
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}
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// Write writes the ELF64 format to the given writer.
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func (elf *ELF) Write(writer io.Writer) {
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binary.Write(writer, binary.LittleEndian, &elf.Header)
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binary.Write(writer, binary.LittleEndian, &elf.ProgramHeader)
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writer.Write([]byte{0, 0, 0, 0, 0, 0, 0, 0})
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writer.Write(elf.Code)
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writer.Write(elf.Data)
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}
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@ -1,13 +0,0 @@
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package elf_test
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import (
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"io"
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"testing"
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"git.akyoto.dev/cli/q/src/elf"
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)
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func TestELF(t *testing.T) {
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exe := elf.New(nil, nil)
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exe.Write(io.Discard)
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}
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@ -1,32 +0,0 @@
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package elf
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const (
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LittleEndian = 1
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TypeExecutable = 2
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ArchitectureAMD64 = 0x3E
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HeaderSize = 64
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)
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// Header contains general information.
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type Header struct {
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Magic [4]byte
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Class byte
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Endianness byte
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Version byte
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OSABI byte
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ABIVersion byte
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_ [7]byte
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Type int16
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Architecture int16
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FileVersion int32
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EntryPointInMemory int64
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ProgramHeaderOffset int64
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SectionHeaderOffset int64
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Flags int32
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Size int16
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ProgramHeaderEntrySize int16
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ProgramHeaderEntryCount int16
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SectionHeaderEntrySize int16
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SectionHeaderEntryCount int16
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SectionNameStringTableIndex int16
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}
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@ -1,37 +0,0 @@
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package elf
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// ProgramHeaderSize is equal to the size of a program header in bytes.
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const ProgramHeaderSize = 56
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// ProgramHeader points to the executable part of our program.
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type ProgramHeader struct {
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Type ProgramType
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Flags ProgramFlags
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Offset int64
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VirtualAddress int64
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PhysicalAddress int64
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SizeInFile int64
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SizeInMemory int64
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Align int64
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}
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type ProgramType int32
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const (
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ProgramTypeNULL ProgramType = 0
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ProgramTypeLOAD ProgramType = 1
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ProgramTypeDYNAMIC ProgramType = 2
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ProgramTypeINTERP ProgramType = 3
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ProgramTypeNOTE ProgramType = 4
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ProgramTypeSHLIB ProgramType = 5
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ProgramTypePHDR ProgramType = 6
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ProgramTypeTLS ProgramType = 7
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)
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type ProgramFlags int32
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const (
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ProgramFlagsExecutable ProgramFlags = 0x1
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ProgramFlagsWritable ProgramFlags = 0x2
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ProgramFlagsReadable ProgramFlags = 0x4
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)
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@ -1,45 +0,0 @@
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package elf
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// SectionHeaderSize is equal to the size of a section header in bytes.
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const SectionHeaderSize = 64
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// SectionHeader points to the data sections of our program.
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type SectionHeader struct {
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NameIndex int32
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Type SectionType
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Flags SectionFlags
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VirtualAddress int64
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Offset int64
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SizeInFile int64
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Link int32
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Info int32
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Align int64
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EntrySize int64
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}
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type SectionType int32
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const (
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SectionTypeNULL SectionType = 0
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SectionTypePROGBITS SectionType = 1
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SectionTypeSYMTAB SectionType = 2
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SectionTypeSTRTAB SectionType = 3
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SectionTypeRELA SectionType = 4
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SectionTypeHASH SectionType = 5
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SectionTypeDYNAMIC SectionType = 6
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SectionTypeNOTE SectionType = 7
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SectionTypeNOBITS SectionType = 8
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SectionTypeREL SectionType = 9
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SectionTypeSHLIB SectionType = 10
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SectionTypeDYNSYM SectionType = 11
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)
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type SectionFlags int64
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const (
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SectionFlagsWritable SectionFlags = 1 << 0
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SectionFlagsAllocate SectionFlags = 1 << 1
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SectionFlagsExecutable SectionFlags = 1 << 2
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SectionFlagsStrings SectionFlags = 1 << 5
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SectionFlagsTLS SectionFlags = 1 << 10
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)
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@ -1,26 +0,0 @@
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# ELF
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## Basic structure
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1. ELF header (0x00 - 0x40)
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2. Program header (0x40 - 0x78)
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3. Padding (0x78 - 0x80)
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4. Machine code (0x80)
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## Entry point
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The entry point is defined in the first 64 bytes (ELF header).
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## Base address
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The minimum base address is controlled by the `mmap` settings:
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```shell
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sysctl vm.mmap_min_addr
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```
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Usually, this value is 65536 (0x1000).
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## Initialization in Linux
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See `/lib/modules/$(uname -r)/build/arch/x86/include/asm/elf.h`.
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