[Mach-O] Do not create a baserel for a subtracted relocation

rui314 · Jul 6, 2022 · a4cc7f3 · a4cc7f3
1 parent be5fe4c
commit a4cc7f3
Show file tree

Hide file tree

Showing 4 changed files with 11 additions and 11 deletions.
diff --git a/macho/arch-arm64.cc b/macho/arch-arm64.cc
@@ -118,12 +118,11 @@ read_relocations(Context<E> &ctx, ObjectFile<E> &file,
 
     Relocation<E> &rel = vec.back();
 
-    if (rels[i].type == ARM64_RELOC_SUBTRACTOR ||
-        (i > 0 && rels[i - 1].type == ARM64_RELOC_SUBTRACTOR)) {
-      rel.is_pcrel = false;
-    } else {
+    if (i > 0 && rels[i - 1].type == ARM64_RELOC_SUBTRACTOR)
+      rel.is_subtracted = true;
+
+    if (!rel.is_subtracted && rels[i].type != ARM64_RELOC_SUBTRACTOR)
       rel.is_pcrel = r.is_pcrel;
-    }
 
     if (r.is_extern) {
       rel.sym = file.syms[r.idx];

diff --git a/macho/arch-x86-64.cc b/macho/arch-x86-64.cc
@@ -95,12 +95,11 @@ read_relocations(Context<E> &ctx, ObjectFile<E> &file,
     vec.push_back({r.offset, (u8)r.type, (u8)r.p2size});
     Relocation<E> &rel = vec.back();
 
-    if (rels[i].type == X86_64_RELOC_SUBTRACTOR ||
-        (i > 0 && rels[i - 1].type == X86_64_RELOC_SUBTRACTOR)) {
-      rel.is_pcrel = false;
-    } else {
+    if (i > 0 && rels[i - 1].type == X86_64_RELOC_SUBTRACTOR)
+      rel.is_subtracted = true;
+
+    if (!rel.is_subtracted && rels[i].type != X86_64_RELOC_SUBTRACTOR)
       rel.is_pcrel = r.is_pcrel;
-    }
 
     if (r.is_extern) {
       rel.sym = file.syms[r.idx];

diff --git a/macho/mold.h b/macho/mold.h
@@ -48,6 +48,7 @@ struct Relocation {
   u8 type = -1;
   u8 p2size = 0;
   bool is_pcrel : 1 = false;
+  bool is_subtracted : 1 = false;
   bool needs_dynrel : 1 = false;
   i64 addend = 0;
   Symbol<E> *sym = nullptr;

diff --git a/macho/output-chunks.cc b/macho/output-chunks.cc
@@ -666,7 +666,8 @@ void RebaseSection<E>::compute_size(Context<E> &ctx) {
       if (chunk->is_output_section && !chunk->hdr.match("__TEXT", "__eh_frame"))
         for (Subsection<E> *subsec : ((OutputSection<E> *)chunk)->members)
           for (Relocation<E> &rel : subsec->get_rels())
-            if (!rel.is_pcrel && rel.type == E::abs_rel && !refers_tls(rel.sym))
+            if (!rel.is_pcrel && !rel.is_subtracted && rel.type == E::abs_rel &&
+                !refers_tls(rel.sym))
               enc.add(seg->seg_idx,
                       subsec->get_addr(ctx) + rel.offset - seg->cmd.vmaddr);