mirror of
https://github.com/roc-lang/roc.git
synced 2025-09-26 21:39:07 +00:00
414 lines
13 KiB
Rust
414 lines
13 KiB
Rust
use object::elf::{self, SectionHeader64};
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use object::read::elf::{FileHeader, ProgramHeader, SectionHeader, Sym};
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use object::Endianness;
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use object::write::elf::Writer;
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use target_lexicon::Triple;
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// an empty shared library, that we build on top of
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const DUMMY_ELF64: &[u8] = include_bytes!("../dummy-elf64-x86-64.so");
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// index of the dynamic section
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const DYMAMIC_SECTION: usize = 4;
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pub fn generate(target: &Triple, custom_names: &[String]) -> object::read::Result<Vec<u8>> {
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match target.binary_format {
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target_lexicon::BinaryFormat::Elf => create_dylib_elf64(DUMMY_ELF64, custom_names),
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target_lexicon::BinaryFormat::Macho => todo!("macho dylib creation"),
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target_lexicon::BinaryFormat::Coff => todo!("coff dylib creation"),
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other => unimplemented!("dylib creation for {:?}", other),
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}
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}
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#[derive(Debug)]
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struct Dynamic {
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tag: u32,
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// Ignored if `string` is set.
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val: u64,
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string: Option<object::write::StringId>,
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}
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#[derive(Debug)]
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struct Symbol {
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in_sym: usize,
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name: Option<object::write::StringId>,
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}
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#[derive(Debug)]
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struct DynamicSymbol {
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in_sym: usize,
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name: Option<object::write::StringId>,
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section: Option<object::write::elf::SectionIndex>,
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gnu_hash: Option<u32>,
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}
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type Section = SectionHeader64<object::Endianness>;
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struct Sections {
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hash: Section,
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gnu_hash: Section,
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dynsym: Section,
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dynstr: Section,
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dynamic: Section,
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}
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#[derive(Default)]
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struct Addresses {
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hash: u64,
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gnu_hash: u64,
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dynsym: u64,
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dynstr: u64,
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dynamic: u64,
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}
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impl Sections {
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fn reserve_alloc_sections(
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&self,
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writer: &mut Writer,
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hash_chain_count: u32,
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gnu_hash_symbol_count: u32,
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dynamic_count: usize,
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) -> ([usize; 5], Addresses) {
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let sections = self;
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let endian = Endianness::Little;
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let mut offsets = [0; 5];
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let mut extra_offset: usize = 0;
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let mut addresses = Addresses::default();
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for (i, out_offset) in offsets.iter_mut().enumerate() {
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// symtab, strtab and shstrtab is ignored because they are not ALLOC
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let in_section = match i {
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0 => sections.hash,
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1 => sections.gnu_hash,
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2 => sections.dynsym,
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3 => sections.dynstr,
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4 => sections.dynamic,
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_ => unreachable!(),
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};
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let offset = in_section.sh_offset(endian) as usize + extra_offset;
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let offset = round_up_to_alignment(offset, 8);
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*out_offset = offset;
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writer.reserve_until(offset);
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let reserved_before = writer.reserved_len();
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match i {
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0 => {
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writer.reserve_hash(3, hash_chain_count);
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}
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1 => {
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addresses.gnu_hash = in_section.sh_addr(endian);
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writer.reserve_gnu_hash(1, 1, gnu_hash_symbol_count);
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}
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2 => {
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addresses.dynsym = in_section.sh_addr(endian);
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writer.reserve_dynsym();
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}
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3 => {
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addresses.dynstr = in_section.sh_addr(endian);
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writer.reserve_dynstr();
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}
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4 => {
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addresses.dynamic = in_section.sh_addr(endian);
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writer.reserve_dynamic(dynamic_count);
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}
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_ => unreachable!(),
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}
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let reserved_after = writer.reserved_len();
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extra_offset += {
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let actual_size = reserved_after - reserved_before;
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actual_size.saturating_sub(in_section.sh_size(endian) as usize)
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};
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}
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(offsets, addresses)
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}
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}
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pub const fn round_up_to_alignment(width: usize, alignment: usize) -> usize {
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match alignment {
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0 => width,
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1 => width,
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_ => {
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if width % alignment > 0 {
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width + alignment - (width % alignment)
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} else {
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width
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}
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}
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}
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}
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fn create_dylib_elf64(in_data: &[u8], custom_names: &[String]) -> object::read::Result<Vec<u8>> {
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let in_elf: &elf::FileHeader64<Endianness> = elf::FileHeader64::parse(in_data)?;
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let endian = in_elf.endian()?;
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let in_segments = in_elf.program_headers(endian, in_data)?;
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let in_sections = in_elf.sections(endian, in_data)?;
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let in_syms = in_sections.symbols(endian, in_data, elf::SHT_SYMTAB)?;
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let in_dynsyms = in_sections.symbols(endian, in_data, elf::SHT_DYNSYM)?;
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let get_section = |name: &[u8]| {
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*in_sections
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.section_by_name(Endianness::Little, name)
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.unwrap()
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.1
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};
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let sections = Sections {
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hash: get_section(b".hash" as &[_]),
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gnu_hash: get_section(b".gnu.hash" as &[_]),
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dynsym: get_section(b".dynsym" as &[_]),
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dynstr: get_section(b".dynstr" as &[_]),
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dynamic: get_section(b".dynamic" as &[_]),
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};
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let mut out_data = Vec::new();
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let mut writer = object::write::elf::Writer::new(endian, in_elf.is_class_64(), &mut out_data);
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let out_sections_index = [
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writer.reserve_hash_section_index(),
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writer.reserve_gnu_hash_section_index(),
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writer.reserve_dynsym_section_index(),
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writer.reserve_dynstr_section_index(),
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writer.reserve_dynamic_section_index(),
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writer.reserve_symtab_section_index(),
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writer.reserve_strtab_section_index(),
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writer.reserve_shstrtab_section_index(),
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];
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// Assign dynamic strings.
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//
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// Dynamic section at offset 0x2268 contains 8 entries:
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// Tag Type Name/Value
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// 0x000000000000000e (SONAME) Library soname: [libapp.so]
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// 0x0000000000000004 (HASH) 0x120
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// 0x000000006ffffef5 (GNU_HASH) 0x130
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// 0x0000000000000005 (STRTAB) 0x168
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// 0x0000000000000006 (SYMTAB) 0x150
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// 0x000000000000000a (STRSZ) 11 (bytes)
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// 0x000000000000000b (SYMENT) 24 (bytes)
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// 0x0000000000000000 (NULL) 0x0
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let dynamic = |tag, val, string| Dynamic { tag, val, string };
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let soname = writer.add_dynamic_string(b"libapp.so");
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let out_dynamic = [
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dynamic(elf::DT_SONAME, 1, Some(soname)),
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dynamic(elf::DT_HASH, 288, None),
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dynamic(elf::DT_GNU_HASH, 304, None),
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dynamic(elf::DT_STRTAB, 360, None),
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dynamic(elf::DT_SYMTAB, 336, None),
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dynamic(elf::DT_STRSZ, 11, None),
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dynamic(elf::DT_SYMENT, 24, None),
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dynamic(elf::DT_NULL, 0, None),
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];
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// Assign dynamic symbol indices.
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let mut out_dynsyms = Vec::with_capacity(in_dynsyms.len());
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for (j, name) in custom_names.iter().enumerate() {
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let i = in_dynsyms.len().saturating_sub(1) + j;
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let in_name = name.as_bytes();
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let name = Some(writer.add_dynamic_string(in_name));
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let gnu_hash = Some(elf::gnu_hash(in_name));
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// .dynamic
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let section = Some(out_sections_index[DYMAMIC_SECTION]);
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out_dynsyms.push(DynamicSymbol {
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in_sym: i,
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name,
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section,
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gnu_hash,
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})
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}
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let mut out_dynsyms_index = vec![Default::default(); in_dynsyms.len() + custom_names.len()];
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for out_dynsym in out_dynsyms.iter_mut() {
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out_dynsyms_index[out_dynsym.in_sym] = writer.reserve_dynamic_symbol_index();
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}
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// Hash parameters.
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let hash_chain_count = writer.dynamic_symbol_count();
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// GNU hash parameters.
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let gnu_hash_index_base = 0;
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let gnu_hash_symbol_base = 1;
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let gnu_hash_symbol_count = writer.dynamic_symbol_count() - gnu_hash_symbol_base;
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// content of the symbol table
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//
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// Symbol table '.symtab' contains 8 entries:
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// Num: Value Size Type Bind Vis Ndx Name
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// 0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND
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// 1: 0000000000000120 0 SECTION LOCAL DEFAULT UND
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// 2: 0000000000000130 0 SECTION LOCAL DEFAULT 1
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// 3: 0000000000000150 0 SECTION LOCAL DEFAULT 2
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// 4: 0000000000000168 0 SECTION LOCAL DEFAULT 3
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// 5: 0000000000001000 0 SECTION LOCAL DEFAULT 4
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// 6: 0000000000001f30 0 SECTION LOCAL DEFAULT 5
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// 7: 0000000000001f30 0 OBJECT LOCAL DEFAULT 5 _DYNAMIC
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let symbol = |index, name| Symbol {
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in_sym: index,
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name,
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};
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let out_syms = [
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symbol(1, None),
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symbol(2, None),
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symbol(3, None),
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symbol(4, None),
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symbol(5, None),
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symbol(6, None),
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symbol(7, Some(writer.add_string(b"_DYNAMIC"))),
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];
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// include the NULL symbol
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let num_local = 1 + out_syms.len();
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let mut out_syms_index = Vec::with_capacity(in_syms.len());
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out_syms_index.push(Default::default());
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for sym in out_syms.iter() {
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out_syms_index.push(writer.reserve_symbol_index(Some(out_sections_index[sym.in_sym])));
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}
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// Start reserving file ranges.
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writer.reserve_file_header();
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// We don't support moving program headers.
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assert_eq!(in_elf.e_phoff(endian), writer.reserved_len() as u64);
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writer.reserve_program_headers(in_segments.len() as u32);
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let (offsets, addresses) = sections.reserve_alloc_sections(
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&mut writer,
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hash_chain_count,
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gnu_hash_symbol_count,
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out_dynamic.len(),
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);
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writer.reserve_symtab();
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writer.reserve_symtab_shndx();
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writer.reserve_strtab();
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writer.reserve_shstrtab();
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writer.reserve_section_headers();
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writer
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.write_file_header(&object::write::elf::FileHeader {
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os_abi: in_elf.e_ident().os_abi,
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abi_version: in_elf.e_ident().abi_version,
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e_type: in_elf.e_type(endian),
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e_machine: in_elf.e_machine(endian),
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e_entry: in_elf.e_entry(endian),
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e_flags: in_elf.e_flags(endian),
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})
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.unwrap();
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writer.write_align_program_headers();
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for in_segment in in_segments {
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writer.write_program_header(&object::write::elf::ProgramHeader {
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p_type: in_segment.p_type(endian),
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p_flags: in_segment.p_flags(endian),
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// dirty hack really. Not sure if this is correct on its own
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p_offset: if in_segment.p_offset(endian) > 0 {
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offsets[DYMAMIC_SECTION] as _
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} else {
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0
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},
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p_vaddr: in_segment.p_vaddr(endian),
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p_paddr: in_segment.p_paddr(endian),
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p_filesz: in_segment.p_filesz(endian),
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p_memsz: in_segment.p_memsz(endian),
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p_align: in_segment.p_align(endian),
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});
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}
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for (i, offset) in offsets.iter().enumerate() {
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writer.pad_until(*offset);
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match i {
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0 => {
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writer.write_hash(1, hash_chain_count, |_| None);
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}
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1 => {
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writer.write_gnu_hash(1, 0, 1, 1, gnu_hash_symbol_count, |index| {
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out_dynsyms[gnu_hash_index_base + index as usize]
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.gnu_hash
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.unwrap()
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});
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}
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2 => {
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writer.write_null_dynamic_symbol();
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for sym in &out_dynsyms {
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writer.write_dynamic_symbol(&object::write::elf::Sym {
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name: sym.name,
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section: sym.section,
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st_info: (elf::STB_GLOBAL << 4) | elf::STT_FUNC,
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st_other: 0,
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st_shndx: 0,
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st_value: 0x1000,
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st_size: 0,
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});
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}
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}
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3 => {
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writer.write_dynstr();
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}
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4 => {
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for d in &out_dynamic {
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if let Some(string) = d.string {
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writer.write_dynamic_string(d.tag, string);
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} else {
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writer.write_dynamic(d.tag, d.val);
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}
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}
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}
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_ => unreachable!(),
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}
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}
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writer.write_null_symbol();
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let section_indices = [0, 1, 2, 3, 4, 5, 5];
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for (sym, sindex) in out_syms.iter().zip(section_indices) {
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let in_sym = in_syms.symbol(sym.in_sym)?;
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writer.write_symbol(&object::write::elf::Sym {
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name: sym.name,
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section: Some(object::write::elf::SectionIndex(sindex)),
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st_info: in_sym.st_info(),
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st_other: in_sym.st_other(),
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st_shndx: in_sym.st_shndx(endian),
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st_value: in_sym.st_value(endian),
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st_size: in_sym.st_size(endian),
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});
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}
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writer.write_symtab_shndx();
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writer.write_strtab();
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writer.write_shstrtab();
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writer.write_null_section_header();
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writer.write_hash_section_header(addresses.hash);
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writer.write_gnu_hash_section_header(addresses.gnu_hash);
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writer.write_dynsym_section_header(addresses.dynsym, 1);
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writer.write_dynstr_section_header(addresses.dynstr);
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writer.write_dynamic_section_header(addresses.dynamic);
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writer.write_symtab_section_header(num_local as _);
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writer.write_strtab_section_header();
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writer.write_shstrtab_section_header();
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debug_assert_eq!(writer.reserved_len(), writer.len());
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Ok(out_data)
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}
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