macho: synthesise missing null records for symbols (again)

kubkon · Dec 3, 2023 · 0f7072e · 0f7072e
1 parent 2374e48
commit 0f7072e
Showing 1 changed file with 31 additions and 12 deletions.
diff --git a/src/MachO/Object.zig b/src/MachO/Object.zig
@@ -563,39 +563,48 @@ fn initUnwindRecords(self: *Object, sect_id: u8, macho_file: *MachO) !void {
         }
     }
 
-    // Synthesise missing unwind records for which we have FDEs available.
+    // Synthesise missing unwind records.
     // The logic here is as follows:
     // 1. if an atom has unwind info record that is not DWARF, FDE is marked dead
     // 2. if an atom has unwind info record that is DWARF, FDE is tied to this unwind record
     // 3. if an atom doesn't have unwind info record but FDE is available, synthesise and tie
-    var superposition = std.AutoArrayHashMap(u64, struct { ?UnwindInfo.Record.Index, ?Fde.Index }).init(gpa);
+    // 4. if an atom doesn't have either, synthesise a null unwind info record
+
+    const Superposition = struct { atom: Atom.Index, size: u64, cu: ?UnwindInfo.Record.Index = null, fde: ?Fde.Index = null };
+
+    var superposition = std.AutoArrayHashMap(u64, Superposition).init(gpa);
     defer superposition.deinit();
-    try superposition.ensureUnusedCapacity(self.unwind_records.items.len + self.fdes.items.len);
+
+    const slice = self.symtab.slice();
+    for (slice.items(.nlist), slice.items(.atom), slice.items(.size)) |nlist, atom, size| {
+        if (!nlist.sect()) continue;
+        const sect = self.sections.items(.header)[nlist.n_sect - 1];
+        if (sect.isCode()) {
+            try superposition.ensureUnusedCapacity(1);
+            superposition.putAssumeCapacityNoClobber(nlist.n_value, .{ .atom = atom, .size = size });
+        }
+    }
 
     for (self.unwind_records.items) |rec_index| {
         const rec = macho_file.getUnwindRecord(rec_index);
         const atom = rec.getAtom(macho_file);
         const addr = atom.getInputAddress(macho_file) + rec.atom_offset;
-        superposition.putAssumeCapacityNoClobber(addr, .{ rec_index, null });
+        superposition.getPtr(addr).?.cu = rec_index;
     }
 
     for (self.fdes.items, 0..) |fde, fde_index| {
         const atom = fde.getAtom(macho_file);
         const addr = atom.getInputAddress(macho_file) + fde.atom_offset;
-        const gop = superposition.getOrPutAssumeCapacity(addr);
-        if (!gop.found_existing) {
-            gop.value_ptr.* = .{ null, null };
-        }
-        gop.value_ptr[1] = @intCast(fde_index);
+        superposition.getPtr(addr).?.fde = @intCast(fde_index);
     }
 
-    for (superposition.values()) |meta| {
+    for (superposition.keys(), superposition.values()) |addr, meta| {
         self.has_unwind = true;
 
-        if (meta[1]) |fde_index| {
+        if (meta.fde) |fde_index| {
             const fde = &self.fdes.items[fde_index];
 
-            if (meta[0]) |rec_index| {
+            if (meta.cu) |rec_index| {
                 const rec = macho_file.getUnwindRecord(rec_index);
                 if (!rec.enc.isDwarf(macho_file)) {
                     // Mark FDE dead
@@ -620,6 +629,16 @@ fn initUnwindRecords(self: *Object, sect_id: u8, macho_file: *MachO) !void {
                 rec.enc.setMode(macho.UNWIND_X86_64_MODE.DWARF);
                 self.has_eh_frame = true;
             }
+        } else if (meta.cu == null and meta.fde == null) {
+            // Create a null record
+            const rec_index = try macho_file.addUnwindRecord();
+            const rec = macho_file.getUnwindRecord(rec_index);
+            const atom = macho_file.getAtom(meta.atom).?;
+            try self.unwind_records.append(gpa, rec_index);
+            rec.length = @intCast(meta.size);
+            rec.atom = meta.atom;
+            rec.atom_offset = @intCast(addr - atom.getInputSection(macho_file).addr - atom.off);
+            rec.file = self.index;
         }
     }