[PATCH] D67054: [yaml2obj] Make e_phoff 0 if there are no program headers

[Alex Brachet via Phabricator via llvm-commits]

abrachet created this revision.
abrachet added reviewers: jhenderson, grimar, MaskRay, rupprecht.
Herald added subscribers: llvm-commits, hiraditya.
Herald added a project: LLVM.

It says here <http://www.sco.com/developers/gabi/latest/ch4.eheader.html> that if there are no program headers than e_phoff should be 0, but currently it is always set after the header. GNU's `readelf` (but not `llvm-readelf`) complains about this: `readelf: Warning: possibly corrupt ELF header - it has a non-zero program header offset, but no program headers`.


https://reviews.llvm.org/D67054

Files:
  llvm/lib/ObjectYAML/ELFEmitter.cpp
  llvm/test/tools/yaml2obj/no-segments-phoff.test


Index: llvm/test/tools/yaml2obj/no-segments-phoff.test
===================================================================
--- /dev/null
+++ llvm/test/tools/yaml2obj/no-segments-phoff.test
@@ -0,0 +1,13 @@
+## Check that e_phoff is set to 0 when there are no program headers
+
+# RUN: yaml2obj %s -o %t
+# RUN: llvm-readobj --file-headers %t | FileCheck %s
+
+# CHECK: ProgramHeaderOffset: 0
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_REL
+  Machine: EM_X86_64
Index: llvm/lib/ObjectYAML/ELFEmitter.cpp
===================================================================
--- llvm/lib/ObjectYAML/ELFEmitter.cpp
+++ llvm/lib/ObjectYAML/ELFEmitter.cpp
@@ -225,7 +225,7 @@
   Header.e_machine = Doc.Header.Machine;
   Header.e_version = EV_CURRENT;
   Header.e_entry = Doc.Header.Entry;
-  Header.e_phoff = sizeof(Header);
+  Header.e_phoff = Doc.ProgramHeaders.size() ? sizeof(Header) : 0;
   Header.e_flags = Doc.Header.Flags;
   Header.e_ehsize = sizeof(Elf_Ehdr);
   Header.e_phentsize = sizeof(Elf_Phdr);


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