[all-commits] [llvm/llvm-project] 08c915: [ELF] -z notext: avoid dynamic relocations in .eh_...

Fangrui Song via All-commits all-commits at lists.llvm.org
Fri Feb 3 10:27:47 PST 2023

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 08c915fa76ef91efa16df0676ed69e4fb360989f
  Author: Fangrui Song <i at maskray.me>
  Date:   2023-02-03 (Fri, 03 Feb 2023)

  Changed paths:
    M lld/ELF/Relocations.cpp
    A lld/test/ELF/eh-frame-znotext.s

  Log Message:
  [ELF] -z notext: avoid dynamic relocations in .eh_frame

Fix https://github.com/llvm/llvm-project/issues/60392

// a.cc
void raise() { throw 42; }
bool foo() {
  try { raise(); } catch (int) { return true; }
  return false;
int main() { foo(); }

clang++ --target=x86_64-linux-gnu -fno-pic -mcmodel=large -no-pie -fuse-ld=lld -z notext a.cc -o a && ./a
clang++ --target=aarch64-linux-gnu -fno-pic -no-pie -fuse-ld=lld -Wl,--dynamic-linker=/usr/aarch64-linux-gnu/lib/ld-linux-aarch64.so.1 -Wl,-rpath=/usr/aarch64-linux-gnu/lib -z notext a.cc -o a && ./a
Both commands fail because we produce a dynamic relocation for
R_X86_64_64/R_AARCH64_ABS64 in .eh_frame which will be adjusted to a wrong
offset by `SectionBase::getOffset` after D122459.

Since GNU ld uses a canonical PLT entry instead of a dynamic relocation for
.eh_frame, we follow suit as well to avoid the issue.

Mips has an ABI issue (https://github.com/llvm/llvm-project/issues/5837) and we
don't implement GNU ld's DW_EH_PE_absptr conversion. mips64-eh-abs-reloc.s wants
a dynamic relocation, so keep the original behavior for EM_MIPS.

Differential Revision: https://reviews.llvm.org/D143136

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