[PATCH] D93331: [ELF] Reject local-exec TLS relocations for -shared

[Fangrui Song via Phabricator via llvm-commits]

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For x86-64, D33100 <https://reviews.llvm.org/D33100> added a diagnostic for local-exec TLS relocations referencing a preemptible symbol.

This patch generalizes it to non-preemptible symbols (see `-Bsymbolic` in `tls.s`)
on all targets.

Local-exec TLS relocations resolve to offsets relative to a fixed point within
the static TLS block, which are only meaningful for the executable.

With this change, `clang -fpic -shared a.c` on the following example will be flagged.

  static __attribute__((tls_model("local-exec"))) __thread long TlsVar = 42;
  long bump() { return ++TlsVar; }

Note, in GNU ld, at least arm, riscv and x86's ports have the similar
diagnostics, but aarch64 and ppc64 do not error.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D93331

Files:
  lld/ELF/Relocations.cpp
  lld/test/ELF/Inputs/i386-static-tls-model4.s
  lld/test/ELF/aarch64-tls-le.s
  lld/test/ELF/arm-tls-le32.s
  lld/test/ELF/i386-static-tls-model.s
  lld/test/ELF/i386-tls-le.s
  lld/test/ELF/i386-zrel-zrela.s
  lld/test/ELF/mips-tls-hilo.s
  lld/test/ELF/ppc64-local-exec-tls.s
  lld/test/ELF/riscv-tls-le.s
  lld/test/ELF/tls.s
  lld/test/ELF/x86-64-reloc-tpoff32-fpic.s

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