v/vlib/compiler/x64/elf.v

101 lines
2.6 KiB
V

// Copyright (c) 2019 Alexander Medvednikov. All rights reserved.
// Use of this source code is governed by an MIT license
// that can be found in the LICENSE file.
module x64
import os
const (
mag0 = 0x7f
mag1 = `E`
mag2 = `L`
mag3 = `F`
ei_class = 4
elfclass64 = 2
elfdata2lsb = 1
ev_current = 1
elf_osabi = 0
// ELF file types
et_rel = 1
et_exec = 2
et_dyn = 3
e_machine = 0x3e
shn_xindex = 0xffff
sht_null = 0
)
const (
segment_start = 0x400000
)
pub fn (g mut Gen) generate_elf_header() {
g.buf << [byte(mag0), mag1, mag2, mag3]
g.buf << elfclass64 // file class
g.buf << elfdata2lsb // data encoding
g.buf << ev_current // file version
g.buf << 1 // elf_osabi
g.write64(0) // et_rel) // et_rel for .o
g.write16(2) // e_type
g.write16(e_machine) //
g.write32(ev_current) // e_version
eh_size := 0x40
phent_size := 0x38
g.write64(segment_start + eh_size + phent_size) // e_entry
g.write64(0x40) // e_phoff
g.write64(0) // e_shoff
g.write32(0) // e_flags
g.write16(eh_size) // e_ehsize
g.write16(phent_size) // e_phentsize
g.write16(1) // e_phnum
g.write16(0) // e_shentsize
g.write16(0) // e_shnum (number of sections)
g.write16(0) // e_shstrndx
// Elf64_Phdr
g.write32(1) // p_type
g.write32(5) // p_flags
g.write64(0) // p_offset
g.write64(segment_start) // p_vaddr addr:050
g.write64(segment_start) //
g.file_size_pos = g.buf.len
g.write64(0) // p_filesz PLACEHOLDER, set to file_size later // addr: 060
g.write64(0) // p_memsz
g.write64(0x1000) // p_align
// user code starts here at
// address: 00070 and a half
g.code_start_pos = g.buf.len
g.call(0) // call main function, it's not guaranteed to be the first
}
pub fn (g mut Gen) generate_elf_footer() {
// Return 0
g.mov(.edi, 0) // ret value
g.mov(.eax, 60)
g.syscall()
// Strings table
// Loop thru all strings and set the right addresses
for i, s in g.strings {
g.write64_at(segment_start + g.buf.len, int(g.str_pos[i]))
g.write_string(s)
g.write8(6)
}
// Now we know the file size, set it
file_size := g.buf.len
g.write64_at(file_size, g.file_size_pos) // set file size 64 bit value
g.write64_at(file_size, g.file_size_pos + 8)
// call main function, it's not guaranteed to be the first
// we generated call(0) ("e8 0")
// no need to replace "0" with a relative address of the main function
// +1 is for "e8"
// -5 is for "e8 00 00 00 00"
g.write64_at(int(g.main_fn_addr - g.code_start_pos) - 5, g.code_start_pos + 1)
// Create the binary
mut f := os.create(g.out_name)or{
panic(err)
}
os.chmod(g.out_name, 0775)
f.write_bytes(g.buf.data, g.buf.len)
f.close()
println('x64 elf binary has been successfully generated')
}