[BPF] Fix .BTF.ext reloc type assigment issue

Commit f1db33c5c1a9 ("[BPF] Disable relocation for .BTF.ext section")
assigned relocation type R_BPF_NONE if the fixup type
is FK_Data_4 and the symbol is temporary.
The reason is we use FK_Data_4 as a fixup type
for insn offsets in .BTF.ext section.

Just checking whether the symbol is temporary is not enough.
For example, .debug_info may reference some strings whose
fixup is FK_Data_4 with a temporary symbol as well.

To truely reflect the case for .BTF.ext section,
this patch further checks that the section associateed with the symbol
must be SHF_ALLOC and SHF_EXECINSTR, i.e., in the text section.
This fixed the above-mentioned problem.

Signed-off-by: Yonghong Song <yhs@fb.com>
llvm-svn: 350637

1 files changed, 10 insertions, 2 deletions

diff --git a/llvm/lib/Target/BPF/MCTargetDesc/BPFELFObjectWriter.cpp b/llvm/lib/Target/BPF/MCTargetDesc/BPFELFObjectWriter.cpp
index 13f6142bb95..32e79d0f527 100644
--- a/llvm/lib/Target/BPF/MCTargetDesc/BPFELFObjectWriter.cpp
+++ b/llvm/lib/Target/BPF/MCTargetDesc/BPFELFObjectWriter.cpp
@@ -57,8 +57,16 @@ unsigned BPFELFObjectWriter::getRelocType(MCContext &Ctx, const MCValue &Target,
     // already been fulfilled by applyFixup(). No
     // further relocation is needed.
     if (const MCSymbolRefExpr *A = Target.getSymA()) {
-      if (A->getSymbol().isTemporary())
-        return ELF::R_BPF_NONE;
+      if (A->getSymbol().isTemporary()) {
+        MCSection &Section = A->getSymbol().getSection();
+        const MCSectionELF *SectionELF = dyn_cast<MCSectionELF>(&Section);
+        assert(SectionELF && "Null section for reloc symbol");
+
+        // The reloc symbol should be in text section.
+        unsigned Flags = SectionELF->getFlags();
+        if ((Flags & ELF::SHF_ALLOC) && (Flags & ELF::SHF_EXECINSTR))
+          return ELF::R_BPF_NONE;
+      }
     }
     return ELF::R_BPF_64_32;
   }