[lld-macho]Use install_name as Identifier for code-sign, if available.

[oontvoo]

Summary

Detail:
LD64 uses the name provided via -[dylib]install_name as "Identifier", when available.
For compatiblity, LLD should do that too.

[oontvoo]

updated test to verify the Identifier field

[oontvoo]

rebase + updated commit msg

[oontvoo]

Hey @keith ! Since you'd added support for the adhoc-codesign stuff, wanna have a quick review on this? TIA!

[keith]

Interestingly this one even takes precedent over -final_output if we ever implement that FIXME

[oontvoo]

Thanks!

lld/MachO/SyntheticSections.cpp

 }
 
 static_assert((CodeSignatureSection::blobHeadersSize % 8) == 0);
 static_assert((CodeSignatureSection::fixedHeadersSize % 8) == 0);
 
 CodeSignatureSection::CodeSignatureSection()
     : LinkEditSection(segment_names::linkEdit, section_names::codeSignature) {
   align = 16; // required by libstuff
+
+  // XXX: This mimics LD64, where it uses the install-name as codesign
+  // identifier, if available.
+  if (!config->installName.empty())
+    fileName = config->installName;
+  else
     // FIXME: Consider using finalOutput instead of outputFile.
     fileName = config->outputFile;
+
   size_t slashIndex = fileName.rfind("/");
   if (slashIndex != std::string::npos)
     fileName = fileName.drop_front(slashIndex + 1);
 
   // NOTE: Any changes to these calculations should be repeated
   // in llvm-objcopy's MachOLayoutBuilder::layoutTail.
   allHeadersSize = alignTo<16>(fixedHeadersSize + fileName.size() + 1);
   fileNamePad = allHeadersSize - fixedHeadersSize - fileName.size();

lld/test/MachO/adhoc-codesign.s

 
 # RUN: %no-arg-lld -lSystem -arch arm64 -platform_version ios-simulator 14.0 15.0 -execute -no_adhoc_codesign -o %t/out %t/main-arm64-sim.o -syslibroot %S/Inputs/iPhoneSimulator.sdk
 # RUN: llvm-objdump --macho --all-headers %t/out| FileCheck --check-prefix=NO-ADHOC %s
 # RUN: %no-arg-lld -arch arm64 -platform_version ios-simulator 14.0 15.0 -dylib   -no_adhoc_codesign -o %t/out %t/foo-arm64-sim.o
 # RUN: llvm-objdump --macho --all-headers %t/out| FileCheck --check-prefix=NO-ADHOC %s
 # RUN: %no-arg-lld -arch arm64 -platform_version ios-simulator 14.0 15.0 -bundle  -no_adhoc_codesign -o %t/out %t/foo-arm64-sim.o
 # RUN: llvm-objdump --macho --all-headers %t/out| FileCheck --check-prefix=NO-ADHOC %s
 
+# RUN: %lld -arch x86_64 -dylib -o %t/out_installname.dylib -install_name @rpath/MyInstallName %t/foo-x86_64-macos.o -adhoc_codesign
+# RUN: %lld -arch x86_64 -dylib -o %t/out_no_installname.dylib %t/foo-x86_64-macos.o -adhoc_codesign
+
+## Smoke check to verify the dataoff and datasize value before using them with code-signature-check.py
+# RUN: llvm-objdump --macho --all-headers %t/out_installname.dylib | FileCheck %s --check-prefix CS-ID-PRE -D#DATA_OFFSET=4176 -D#DATA_SIZE=192 
+# RUN: llvm-objdump --macho --all-headers %t/out_no_installname.dylib | FileCheck %s --check-prefix CS-ID-PRE -D#DATA_OFFSET=4176 -D#DATA_SIZE=208 
+
+## Verify that the 'Identifier' (aka 'Code Directory ID') field are set to the install-name, if available.
+# RUN: %python %p/Inputs/code-signature-check.py %t/out_installname.dylib 4176 192 0 4176 | FileCheck %s --check-prefix CS-ID-INSTALL
+# RUN:  %python %p/Inputs/code-signature-check.py %t/out_no_installname.dylib 4176 208 0 4176 | FileCheck %s --check-prefix CS-ID-NO-INSTALL
+
 # ADHOC:          cmd LC_CODE_SIGNATURE
 # ADHOC-NEXT: cmdsize 16
 
 # NO-ADHOC-NOT:          cmd LC_CODE_SIGNATURE
 
+# CS-ID-PRE: cmd LC_CODE_SIGNATURE
+# CS-ID-PRE-NEXT: cmdsize 16
+# CS-ID-PRE-NEXT: dataoff [[#DATA_OFFSET]]
+# CS-ID-PRE-NEXT: datasize [[#DATA_SIZE]]
+
+# CS-ID-INSTALL: Code Directory ID: MyInstallName
+# CS-ID-NO-INSTALL: Code Directory ID: out_no_installname.dylib
+
 #--- foo.s
 .globl _foo
 _foo:
   ret
 
 #--- main.s
 .globl _main
 _main:
   ret