[PATCH] D77368: [ELF] Allow invalid sh_size%sh_entsize!=0 for non-SHF_MERGE sections

[Fangrui Song via Phabricator via llvm-commits]

MaskRay created this revision.
MaskRay added reviewers: grimar, psmith, ruiu.
Herald added subscribers: llvm-commits, arichardson, emaste.
Herald added a reviewer: espindola.
Herald added a project: LLVM.

Fixes https://bugs.llvm.org/show_bug.cgi?id=45370

.stab holds a table of 12-byte entries. GNU as incorrectly sets
sh_entsize(.stab) to 20 on 64-bit architectures.
https://sourceware.org/bugzilla/show_bug.cgi?id=25768

We should not emit the confusing error:
"SHF_MERGE section size (...) must be a multiple of sh_entsize (20)


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D77368

Files:
  lld/ELF/InputFiles.cpp
  lld/test/ELF/invalid/entsize.yaml


Index: lld/test/ELF/invalid/entsize.yaml
===================================================================
--- /dev/null
+++ lld/test/ELF/invalid/entsize.yaml
@@ -0,0 +1,15 @@
+## Ignore invalid sh_entsize (sh_size%sh_entsize!=0) for non-SHF_MERGE sections.
+# RUN: yaml2obj %s -o %t.o
+# RUN: ld.lld -e 0 --fatal-warnings %t.o -o /dev/null
+
+!ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_REL
+  Machine: EM_X86_64
+Sections:
+  - Name:    .stab
+    Type:    SHT_PROGBITS
+    EntSize: 20
+    Size:    24
Index: lld/ELF/InputFiles.cpp
===================================================================
--- lld/ELF/InputFiles.cpp
+++ lld/ELF/InputFiles.cpp
@@ -446,6 +446,10 @@
   if (sec.sh_size == 0)
     return false;
 
+  uint64_t flags = sec.sh_flags;
+  if (!(flags & SHF_MERGE))
+    return false;
+
   // Check for sh_entsize. The ELF spec is not clear about the zero
   // sh_entsize. It says that "the member [sh_entsize] contains 0 if
   // the section does not hold a table of fixed-size entries". We know
@@ -459,9 +463,6 @@
           Twine(sec.sh_size) + ") must be a multiple of sh_entsize (" +
           Twine(entSize) + ")");
 
-  uint64_t flags = sec.sh_flags;
-  if (!(flags & SHF_MERGE))
-    return false;
   if (flags & SHF_WRITE)
     fatal(toString(this) + ":(" + name +
           "): writable SHF_MERGE section is not supported");


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