[llvm] 9c97aa5 - [llvm-objcopy] Always update indirectsymoff in MachO (#117726)

[via llvm-commits]

Author: Richard Dzenis
Date: 2024-11-29T12:27:12+02:00
New Revision: 9c97aa5abb6aa4ce4055095a89ae7d72e1b61803

URL: https://github.com/llvm/llvm-project/commit/9c97aa5abb6aa4ce4055095a89ae7d72e1b61803
DIFF: https://github.com/llvm/llvm-project/commit/9c97aa5abb6aa4ce4055095a89ae7d72e1b61803.diff

LOG: [llvm-objcopy] Always update indirectsymoff in MachO (#117726)

Let's say we've run llvm-strip over some MachO. The resulting MachO
became smaller and there are no indirect symbols anymore.

Then according to previous code we would not update indirectsymoff
field. This would lead to `MachOWriter::totalSize()` report size that is
larger than the new MachO. As a result we would get MachO that has zero
bytes past contents of the very last load command.

Codesign has a strict check that size of MachO file must be equal to

    lastLoadCommand.offset + lastLoadCommand.size

If this is not satisfied codesign reports the following error

    main executable failed strict validation

Fixes #117723

Added: 
    llvm/test/tools/llvm-objcopy/MachO/dysymtab-zero-indirectsym.test

Modified: 
    llvm/lib/ObjCopy/MachO/MachOLayoutBuilder.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/ObjCopy/MachO/MachOLayoutBuilder.cpp b/llvm/lib/ObjCopy/MachO/MachOLayoutBuilder.cpp
index a3d4ba3a94f7ac..93bc6631e64c86 100644
--- a/llvm/lib/ObjCopy/MachO/MachOLayoutBuilder.cpp
+++ b/llvm/lib/ObjCopy/MachO/MachOLayoutBuilder.cpp
@@ -360,13 +360,10 @@ Error MachOLayoutBuilder::layoutTail(uint64_t Offset) {
           MLC.dysymtab_command_data.nextrel != 0)
         return createStringError(llvm::errc::not_supported,
                                  "shared library is not yet supported");
-
-      if (!O.IndirectSymTable.Symbols.empty()) {
-        MLC.dysymtab_command_data.indirectsymoff = StartOfIndirectSymbols;
-        MLC.dysymtab_command_data.nindirectsyms =
-            O.IndirectSymTable.Symbols.size();
-      }
-
+      MLC.dysymtab_command_data.indirectsymoff =
+          O.IndirectSymTable.Symbols.size() ? StartOfIndirectSymbols : 0;
+      MLC.dysymtab_command_data.nindirectsyms =
+          O.IndirectSymTable.Symbols.size();
       updateDySymTab(MLC);
       break;
     }

diff  --git a/llvm/test/tools/llvm-objcopy/MachO/dysymtab-zero-indirectsym.test b/llvm/test/tools/llvm-objcopy/MachO/dysymtab-zero-indirectsym.test
new file mode 100644
index 00000000000000..bdfb8b809928d0
--- /dev/null
+++ b/llvm/test/tools/llvm-objcopy/MachO/dysymtab-zero-indirectsym.test
@@ -0,0 +1,48 @@
+## Show that llvm-strip correctly zeroes out indirectsymoff and indirectsyms
+## in LC_DYSYMTAB if there are no symbols
+#
+# RUN: yaml2obj %s -o %t
+# RUN: llvm-strip --strip-all %t -o %t.stripped
+# RUN: obj2yaml %t.stripped | FileCheck %s
+
+# CHECK: indirectsymoff: 0
+# CHECK-NEXT: nindirectsyms: 0
+
+--- !mach-o
+FileHeader:
+  magic:           0xFEEDFACF
+  cputype:         0x01000007
+  cpusubtype:      0x80000003
+  filetype:        0x00000002
+  ncmds:           2
+  sizeofcmds:      104
+  flags:           0x00200085
+  reserved:        0x00000000
+LoadCommands:
+  - cmd:             LC_SYMTAB
+    cmdsize:         24
+    symoff:          0
+    nsyms:           0
+    stroff:          0
+    strsize:         0
+  - cmd:             LC_DYSYMTAB
+    cmdsize:         80
+    ilocalsym:       0
+    nlocalsym:       0
+    iextdefsym:      0
+    nextdefsym:      0
+    iundefsym:       0
+    nundefsym:       0
+    tocoff:          0
+    ntoc:            0
+    modtaboff:       0
+    nmodtab:         0
+    extrefsymoff:    0
+    nextrefsyms:     0
+    indirectsymoff:  42
+    nindirectsyms:   0
+    extreloff:       0
+    nextrel:         0
+    locreloff:       0
+    nlocrel:         0
+...