[all-commits] [llvm/llvm-project] daaaed: [lld-macho] Fix TLV data initialization

[Jez Ng via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: daaaed6bb89044ac58a23f1bb1ccdd12342a5a58
      https://github.com/llvm/llvm-project/commit/daaaed6bb89044ac58a23f1bb1ccdd12342a5a58
  Author: Jez Ng <jezng at fb.com>
  Date:   2021-01-08 (Fri, 08 Jan 2021)

  Changed paths:
    M lld/MachO/InputSection.cpp
    M lld/MachO/InputSection.h
    M lld/MachO/Writer.cpp
    M lld/MachO/Writer.h
    M lld/test/MachO/bss.s
    M lld/test/MachO/tlv.s

  Log Message:
  -----------
  [lld-macho] Fix TLV data initialization

We were mishandling the case where both `__tbss` and `__thread_data` sections were
present.

TLVP relocations should be encoded as offsets from the start of `__thread_data`,
even if the symbol is actually located in `__thread_bss`. Previously, we were
writing the offset from the start of the containing section, which doesn't
really make sense since there's no way `tlv_get_addr()` can know which section a
given `tlv$init` symbol is in at runtime.

In addition, this patch ensures that we place `__thread_data` immediately before
`__thread_bss`. This is what ld64 does, likely for performance reasons. Zerofill
sections must also be at the end of their segments; we were already doing this,
but now we ensure that `__thread_bss` occurs before `__bss`, so that it's always
possible to have it contiguous with `__thread_data`.

Fixes llvm.org/PR48657.

Reviewed By: #lld-macho, thakis

Differential Revision: https://reviews.llvm.org/D94329