port(MachO): Align __LINKEDIT sections

libwild/src/macho.rs

@@ -1318,7 +1318,10 @@ impl platform::Platform for MachO {
         fixup_table_size += CHAINED_FIXUP_PAGE_START_SIZE
             * (state.imported_symbols.len() as u64).div_ceil(MACHO_PAGE_ALIGNMENT.value());
 
-        mem_sizes.increment(part_id::CHAINED_FIXUP_TABLE, fixup_table_size);
+        mem_sizes.increment(
+            part_id::CHAINED_FIXUP_TABLE,
+            alignment::USIZE.align_up(fixup_table_size),
+        );
     }
 
     fn finalise_sizes_all<'data>(
@@ -1709,10 +1712,12 @@ const SECTION_DEFINITIONS: [BuiltInSectionDetails; NUM_BUILT_IN_SECTIONS] = {
     };
     defs[output_section_id::CHAINED_FIXUP_TABLE.as_usize()] = BuiltInSectionDetails {
         kind: SectionKind::Primary(SectionName(b"DYLD_CHAINED_FIXUPS_TABLE")),
+        min_alignment: alignment::USIZE,
         ..DEFAULT_DEFS
     };
     defs[output_section_id::SYMTAB_GLOBAL.as_usize()] = BuiltInSectionDetails {
         kind: SectionKind::Primary(SectionName(b"SYMTAB")),
+        min_alignment: alignment::USIZE,
         ..DEFAULT_DEFS
     };
     defs[output_section_id::CODE_SIGNATURE.as_usize()] = BuiltInSectionDetails {

linker-diff/src/header_diff.rs

@@ -22,14 +22,20 @@ use object::ObjectSymbol as _;
 use object::Section;
 #[allow(clippy::wildcard_imports)]
 use object::elf::*;
+use object::macho::LC_CODE_SIGNATURE;
+use object::macho::LC_DYLD_CHAINED_FIXUPS;
 use object::read::elf::Dyn;
+use object::read::macho::LoadCommandVariant;
 use object::read::macho::MachHeader;
 use std::borrow::Cow;
 use std::collections::BTreeSet;
 use tabled::Table;
 use tabled::settings::Style;
 use tabled::settings::style::HorizontalLine;
 
+const MACHO64_LINKEDIT_ALIGNMENT: u32 = 8;
+const MACHO_CODE_SIGNATURE_ALIGNMENT: u32 = 16;
+
 #[derive(Clone, Copy)]
 pub(crate) enum Converter {
     None,
@@ -198,6 +204,15 @@ pub(crate) fn check_dynamic_headers(report: &mut Report, objects: &[crate::Binar
     ));
 }
 
+pub(crate) fn check_macho_linkedit_alignment(report: &mut Report, objects: &[crate::Binary]) {
+    report.add_diffs(diff_fields(
+        objects,
+        read_macho_linkedit_fields,
+        "linkedit",
+        DiffMode::IgnoreMissingValues,
+    ));
+}
+
 pub(crate) fn report_section_diffs(report: &mut Report, objects: &[Binary]) {
     // Find section names defined by our first reference object. We ignore empty sections though,
     // since Wild will output empty sections if they have start/stop symbols that are referenced.
@@ -709,3 +724,49 @@ fn read_dynamic_fields(obj: &Binary) -> Result<FieldValues> {
 
     Ok(values)
 }
+
+fn read_macho_linkedit_fields(obj: &Binary) -> Result<FieldValues> {
+    let mut values = FieldValues::default();
+    let object::File::MachO64(file) = obj.file else {
+        return Ok(values);
+    };
+    let e = file.endianness();
+    let mut load_commands = file.macho_load_commands()?;
+
+    while let Some(load_command) = load_commands.next()? {
+        match load_command.variant()? {
+            LoadCommandVariant::Symtab(symtab) => {
+                values.insert_string(
+                    "SYMTAB.symoff.alignment",
+                    format_alignment(symtab.symoff.get(e), MACHO64_LINKEDIT_ALIGNMENT),
+                );
+            }
+            LoadCommandVariant::LinkeditData(linkedit) => match linkedit.cmd.get(e) {
+                LC_DYLD_CHAINED_FIXUPS => {
+                    values.insert_string(
+                        "DYLD_CHAINED_FIXUPS.dataoff.alignment",
+                        format_alignment(linkedit.dataoff.get(e), MACHO64_LINKEDIT_ALIGNMENT),
+                    );
+                }
+                LC_CODE_SIGNATURE => {
+                    values.insert_string(
+                        "CODE_SIGNATURE.dataoff.alignment",
+                        format_alignment(linkedit.dataoff.get(e), MACHO_CODE_SIGNATURE_ALIGNMENT),
+                    );
+                }
+                _ => {}
+            },
+            _ => {}
+        }
+    }
+
+    Ok(values)
+}
+
+fn format_alignment(offset: u32, alignment: u32) -> String {
+    if offset.is_multiple_of(alignment) {
+        "OK".to_owned()
+    } else {
+        format!("offset 0x{offset:x} is not {alignment}-byte aligned")
+    }
+}

linker-diff/src/lib.rs

@@ -674,6 +674,7 @@ impl Report {
         );
         header_diff::check_dynamic_headers(self, objects);
         header_diff::check_file_headers(self, objects);
+        header_diff::check_macho_linkedit_alignment(self, objects);
         header_diff::report_section_diffs(self, objects);
         eh_frame_diff::report_diffs(self, objects);
         version_diff::report_diffs(self, objects);