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local ELFVERSION <const> = 1
---@enum Osabi
local Osabi <const> = {
sysv = 0x00,
hpux = 0x01,
netbsd = 0x02,
linux = 0x03,
hurd = 0x04,
solaris = 0x06,
aix = 0x07,
irix = 0x08,
freebsd = 0x09,
tru64 = 0x0a,
modesto = 0x0b,
openbsd = 0x0c,
openvms = 0x0d,
nsk = 0x0e,
aros = 0x0f,
fenixos = 0x10,
cloudabi = 0x11,
opevos = 0x12,
}
---@enum Class
local Class <const> = {
bit32 = 0x1,
bit64 = 0x2,
}
---@enum Endian
local Endian <const> = {
little = 0x1,
big = 0x2,
}
---@enum Type
local Type <const> = {
none = 0x00,
rel = 0x01,
exec = 0x02,
dyn = 0x03,
core = 0x04,
loos = 0xfe00,
hios = 0xfeff,
loproc = 0xfe00,
hiproc = 0xfeff,
}
---@enum Machine
local Machine <const> = {
none = 0x00,
m32 = 0x01, -- AT&T WE 32100
sparc = 0x02, -- SPARC
i386 = 0x03, -- Intel 80386
m68k = 0x04, -- Motorola 68000 (M68k)
m88k = 0x05, -- Motorola 88000 (M88k)
mcu = 0x06, -- Intel MCU
i860 = 0x07, -- Intel 80860
mips = 0x08, -- MIPS
s370 = 0x09, -- IBM System/370
mipsrs3le = 0x0a, -- MIPS RS3000 Little Endian
parisc = 0x0f, -- Hewlett-Packard PA-RISC
vpp500 = 0x11, -- Fujitsu VPP500
sparc32 = 0x12, -- Enhanced instruction set SPARC
i960 = 0x13, -- Intel 80960
ppc = 0x14, -- PowerPC
ppc64 = 0x15, -- PowerPC (64-bit)
s390 = 0x16, -- IBM System/390
spu = 0x17, -- IBM SPC/SPU
v800 = 0x24, -- NEC V800
fr20 = 0x25, -- Fujitsu FR20
-- todo
}
---@alias ElfMagic [integer, integer, integer, integer]
---@class ElfHeader
---@field magic ElfMagic
---@field class Class
---@field data Endian
---@field ident_version integer
---@field osabi Osabi
---@field abiversion integer
---@field type Type
---@field machine Machine
---@field version integer
---@field entry integer
---@field phoff integer
---@field shoff integer
---@field flags integer
---@field ehsize integer
---@field phentsize integer
---@field phnum integer
---@field shentsize integer
---@field shnum integer
---@field shstrndx integer
---@param endian Endian
---@nodiscard
local function efmt(endian)
return (endian == Endian.big) and ">" or "<"
end
---@param class Class
---@nodiscard
local function szfmt(class)
return (class == Class.bit64) and "I8" or "I4"
end
---@param hdr ElfHeader
---@nodiscard
local function ElfHeader_pack(hdr)
return string.pack("BBBBBBBBBxxxxxxx" ..
efmt(hdr.data) ..
"I2I2I4" ..
string.rep(szfmt(hdr.class), 3) ..
"I4I2I2I2I2I2I2",
hdr.magic[1], hdr.magic[2], hdr.magic[3], hdr.magic[4],
hdr.class,
hdr.data,
hdr.ident_version,
hdr.osabi,
hdr.abiversion,
hdr.type,
hdr.machine,
hdr.version,
hdr.entry,
hdr.phoff,
hdr.shoff,
hdr.flags,
hdr.ehsize,
hdr.phentsize,
hdr.phnum,
hdr.shentsize,
hdr.shnum,
hdr.shstrndx)
end
---@class ProgramHeaders
---@field type integer
---@field flags integer
---@field offset integer
---@field vaddr integer
---@field paddr integer
---@field filesz integer
---@field memsz integer
---@field align integer
---@enum SegmentType
local SegmentType <const> = {
null = 0x00000000,
load = 0x00000001,
dynamic = 0x00000002,
interp = 0x00000003,
note = 0x00000004,
shlib = 0x00000005,
phdr = 0x00000006,
tls = 0x00000007,
loos = 0x60000000,
hios = 0x6FFFFFFF,
loproc = 0x70000000,
hiproc = 0x7FFFFFFF,
}
---@enum SegmentFlags
local SegmentFlags <const> = {
x = 0x1,
w = 0x2,
r = 0x3,
}
---@param hdr ProgramHeaders
---@param endian Endian
---@param class Class
---@nodiscard
local function ElfPHeader_pack(hdr, endian, class)
if class == Class.bit32 then
return string.pack(efmt(endian) .. string.rep(szfmt(class), 8),
hdr.type,
hdr.offset,
hdr.vaddr,
hdr.paddr,
hdr.filesz,
hdr.memsz,
hdr.flags,
hdr.align)
elseif class == Class.bit64 then
return string.pack(efmt(endian) .. "I4I4" .. string.rep(szfmt(class), 6),
hdr.type,
hdr.flags,
hdr.offset,
hdr.vaddr,
hdr.paddr,
hdr.filesz,
hdr.memsz,
hdr.align)
end
end
local function main()
---@type ElfHeader
local header <const> = {
magic = { 0x7f, 0x45, 0x4c, 0x46 },
class = Class.bit32,
data = Endian.big,
ident_version = ELFVERSION,
osabi = Osabi.netbsd,
abiversion = 0,
type = Type.exec,
machine = Machine.i386,
version = ELFVERSION,
entry = 0,
phoff = 0x34,
shoff = 0xff,
flags = 0,
ehsize = 52,
phentsize = 0x20,
phnum = 0,
shentsize = 0x28,
shnum = 0,
shstrndx = 0,
}
---@type ProgramHeaders
local pheader <const> = {
type = SegmentType.dynamic,
flags = SegmentFlags.x,
offset = 0xf,
vaddr = 0xff,
paddr = 0xfff,
filesz = 0xffff,
memsz = 0xfffff,
align = 1,
}
local output = "a.out"
for i in ipairs(arg) do
if arg[i] ~= "-o" then goto continue end
if not arg[i + 1] then
error("mkelf: missing filename after -o")
end
output = arg[i + 1]
::continue::
end
local f = assert(io.open(output, "w"))
f:write(ElfHeader_pack(header))
f:write(ElfPHeader_pack(pheader, header.data, header.class))
f:close()
end
main()
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