[PATCH] D82479: [llvm-size] Output REL, RELA and STRTAB sections in some cases

[Owen Reynolds via Phabricator via llvm-commits]

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

gnu size has a number of special cases regarding REL, RELA and STRTAB sections being considered in size output. To avoid unnecessary complexity this commit makes llvm size outputs these sections in cases they have the SHF_ALLOC flag. See related bugzilla:

https://bugs.llvm.org/show_bug.cgi?id=42934


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D82479

Files:
  llvm/test/tools/llvm-size/output-alloc.test
  llvm/tools/llvm-size/llvm-size.cpp


Index: llvm/tools/llvm-size/llvm-size.cpp
===================================================================
--- llvm/tools/llvm-size/llvm-size.cpp
+++ llvm/tools/llvm-size/llvm-size.cpp
@@ -180,6 +180,30 @@
   return nullptr;
 }
 
+static uint64_t getShstrndx(ObjectFile *Obj) {
+  if (const auto *ELFObj = dyn_cast<object::ELF32LEObjectFile>(Obj))
+    return ELFObj->getELFFile()->getHeader()->e_shstrndx;
+
+  if (const auto *ELFObj = dyn_cast<object::ELF32BEObjectFile>(Obj))
+    return ELFObj->getELFFile()->getHeader()->e_shstrndx;
+
+  if (const auto *ELFObj = dyn_cast<object::ELF64LEObjectFile>(Obj))
+    return ELFObj->getELFFile()->getHeader()->e_shstrndx;
+
+  const auto *ELFObj = dyn_cast<object::ELF64BEObjectFile>(Obj);
+  return ELFObj->getELFFile()->getHeader()->e_shstrndx;
+}
+
+static bool isAllocatable(ObjectFile *Obj, SectionRef Section) {
+  if (Section.getIndex() == getShstrndx(Obj))
+    return false;
+
+  ELFSectionRef ElfSection = static_cast<ELFSectionRef>(Section);
+  if (ElfSection.getFlags() & ELF::SHF_ALLOC)
+    return true;
+  return false;
+}
+
 /// Remove unneeded ELF sections from calculation
 static bool considerForSize(ObjectFile *Obj, SectionRef Section) {
   if (!Obj->isELF())
@@ -187,10 +211,11 @@
   switch (static_cast<ELFSectionRef>(Section).getType()) {
   case ELF::SHT_NULL:
   case ELF::SHT_SYMTAB:
+    return false;
   case ELF::SHT_STRTAB:
   case ELF::SHT_REL:
   case ELF::SHT_RELA:
-    return false;
+    return isAllocatable(Obj, Section);
   }
   return true;
 }
Index: llvm/test/tools/llvm-size/output-alloc.test
===================================================================
--- /dev/null
+++ llvm/test/tools/llvm-size/output-alloc.test
@@ -0,0 +1,38 @@
+## gnu size has a number of special cases regarding REL, RELA and STRTAB sections being considered in size output. 
+## To avoid unnecessary complexity llvm size outputs these sections in cases they have the SHF_ALLOC flag.
+
+# RUN: yaml2obj %s -o %t1
+# RUN: llvm-size --format=sysv %t1 | FileCheck %s
+
+# CHECK:      section     size   addr
+# CHECK-NEXT: .rela.alloc
+# CHECK-NEXT: .rel.alloc
+# CHECK-NEXT: .strtab.alloc
+# CHECK-NEXT: Total
+# CHECK-EMPTY:
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_REL
+  Machine: EM_X86_64
+Sections:
+  - Name:  .rela.alloc
+    Type:  SHT_RELA
+    Flags: [ SHF_ALLOC ]
+  - Name:  .rel.alloc
+    Type:  SHT_REL
+    Flags: [ SHF_ALLOC ]
+  - Name:  .strtab.alloc
+    Type:  SHT_STRTAB
+    Flags: [ SHF_ALLOC ]
+  - Name:  .rela
+    Type:  SHT_RELA
+    Flags: []
+  - Name:  .rel
+    Type:  SHT_REL
+    Flags: []
+  - Name:  .strtab
+    Type:  SHT_STRTAB
+    Flags: []


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