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linker/macho: record start of first section following load commands

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Jakub Konka 2025-01-07 23:24:33 +01:00
parent 5d0b700730
commit 93a4e9924d
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1 changed files with 18 additions and 105 deletions
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123
crates/linker/src/macho.rs
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@ -51,11 +51,6 @@ struct SurgeryEntry {
size: u8,
}
// TODO: Reanalyze each piece of data in this struct.
// I think a number of them can be combined to reduce string duplication.
// Also I think a few of them aren't need.
// For example, I think preprocessing can deal with all shifting and remove the need for added_byte_count.
// TODO: we probably should be storing numbers in an endian neutral way.
#[derive(Default, Serialize, Deserialize, PartialEq, Eq, Debug)]
struct Metadata {
app_functions: Vec<String>,
@ -63,17 +58,13 @@ struct Metadata {
plt_addresses: MutMap<String, (u64, u64)>,
surgeries: MutMap<String, Vec<SurgeryEntry>>,
dynamic_symbol_indices: MutMap<String, u64>,
_static_symbol_indices: MutMap<String, u64>,
roc_symbol_vaddresses: MutMap<String, u64>,
exec_len: u64,
load_align_constraint: u64,
added_byte_count: u64,
last_vaddr: u64,
_dynamic_section_offset: u64,
_dynamic_symbol_table_section_offset: u64,
_symbol_table_section_offset: u64,
_symbol_table_size: u64,
macho_cmd_loc: u64,
start_of_first_section: u64,
}
impl Metadata {
@ -357,8 +348,9 @@ pub(crate) fn preprocess_macho_le(
let mut stubs_symbol_index = None;
let mut stubs_symbol_count = None;
let mut start_of_first_section = None;
'cmds: for _ in 0..num_load_cmds {
for _ in 0..num_load_cmds {
let info = load_struct_inplace::<macho::LoadCommand<LE>>(exec_data, offset);
let cmd = info.cmd.get(LE);
let cmdsize = info.cmdsize.get(LE);
@ -380,8 +372,11 @@ pub(crate) fn preprocess_macho_le(
stubs_symbol_index = Some(section_info.reserved1.get(LE));
stubs_symbol_count =
Some(section_info.size.get(LE) / STUB_ADDRESS_OFFSET);
break 'cmds;
}
if section_info.size.get(LE) > 0 {
let offset = section_info.offset.get(LE) as u64;
let inner = start_of_first_section.get_or_insert(offset);
*inner = std::cmp::min(*inner, offset);
}
}
}
@ -390,6 +385,16 @@ pub(crate) fn preprocess_macho_le(
offset += cmdsize as usize;
}
md.start_of_first_section = start_of_first_section.unwrap_or_else(|| {
internal_error!("Could not establish offset of first section following load commands");
});
if verbose {
println!(
"Found start of first section following load commands: {}",
md.start_of_first_section
);
}
let stubs_symbol_index = stubs_symbol_index.unwrap_or_else(|| {
panic!("Could not find stubs symbol index.");
});
@ -503,15 +508,6 @@ pub(crate) fn preprocess_macho_le(
let scanning_dynamic_deps_start = Instant::now();
// let ElfDynamicDeps {
// got_app_syms,
// got_sections,
// dynamic_lib_count,
// shared_lib_index,
// } = scan_elf_dynamic_deps(
// &exec_obj, &mut md, &app_syms, shared_lib, exec_data, verbose,
// );
let scanning_dynamic_deps_duration = scanning_dynamic_deps_start.elapsed();
let platform_gen_start = Instant::now();
@ -671,16 +667,6 @@ fn gen_macho_le(
// Go through every command and shift it by added_bytes if it's absolute, unless it's inside the command header
let mut offset = mem::size_of_val(exec_header);
// TODO: Add this back in the future when needed.
// let cpu_type = match target.architecture {
// target_lexicon::Architecture::X86_64 => macho::CPU_TYPE_X86_64,
// target_lexicon::Architecture::Aarch64(_) => macho::CPU_TYPE_ARM64,
// _ => {
// // We should have verified this via supported() before calling this function
// unreachable!()
// }
// };
// minus one because we "deleted" a load command
for _ in 0..(num_load_cmds - 1) {
let info = load_struct_inplace::<macho::LoadCommand<LE>>(&out_mmap, offset);
@ -709,79 +695,6 @@ fn gen_macho_le(
.set(LE, cmd.filesize.get(LE) + md.added_byte_count);
cmd.vmsize.set(LE, cmd.vmsize.get(LE) + md.added_byte_count);
}
// let num_sections = cmd.nsects.get(LE);
// let sections = load_structs_inplace_mut::<macho::Section64<LE >>(
// &mut out_mmap,
// offset + mem::size_of::<macho::SegmentCommand64<LE >>(),
// num_sections as usize,
// );
// struct Relocation {
// offset: u32,
// num_relocations: u32,
// }
// let mut relocation_offsets = Vec::with_capacity(sections.len());
// for section in sections {
// section.addr.set(
// LE ,
// section.addr.get(LE) + md.added_byte_count as u64,
// );
// // If offset is zero, don't update it.
// // Zero is used for things like BSS that don't exist in the file.
// let old_offset = section.offset.get(LE);
// if old_offset > 0 {
// section
// .offset
// .set(LE , old_offset + md.added_byte_count as u32);
// }
// if section.nreloc.get(LE) > 0 {
// section.reloff.set(
// LE ,
// section.reloff.get(LE) + md.added_byte_count as u32,
// );
// }
// relocation_offsets.push(Relocation {
// offset: section.reloff.get(LE),
// num_relocations: section.nreloc.get(LE),
// });
// }
// TODO FIXME this is necessary for ARM, but seems to be broken. Skipping for now since we're just targeting x86
// for Relocation {
// offset,
// num_relocations,
// } in relocation_offsets
// {
// let relos = load_structs_inplace_mut::<macho::Relocation<LE >>(
// &mut out_mmap,
// offset as usize,
// num_relocations as usize,
// );
// // TODO this has never been tested, because scattered relocations only come up on ARM!
// for relo in relos.iter_mut() {
// if relo.r_scattered(LE , cpu_type) {
// let mut scattered_info = relo.scattered_info(LE);
// if !scattered_info.r_pcrel {
// scattered_info.r_value += md.added_byte_count as u32;
// let new_info = scattered_info.relocation(LE );
// relo.r_word0 = new_info.r_word0;
// relo.r_word1 = new_info.r_word1;
// }
// }
// }
// }
// TODO this seems to be wrong and unnecessary, and should probably be deleted.
// offset += num_sections as usize * mem::size_of::<macho::Section64<LE >>();
}
macho::LC_SYMTAB => {
let cmd =