[all-commits] [llvm/llvm-project] a33687: [RuntimeDyld] Add allowStubs/allowZeroSyms

[Rafael Auler via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: a33687ec584d18dc0d092853d583d7116808459c
      https://github.com/llvm/llvm-project/commit/a33687ec584d18dc0d092853d583d7116808459c
  Author: Rafael Auler <rafaelauler at fb.com>
  Date:   2021-05-18 (Tue, 18 May 2021)

  Changed paths:
    M llvm/include/llvm/ExecutionEngine/JITSymbol.h
    M llvm/include/llvm/ExecutionEngine/RuntimeDyld.h
    M llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp
    M llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.cpp

  Log Message:
  -----------
  [RuntimeDyld] Add allowStubs/allowZeroSyms

This patch introduces functionality used by BOLT when
re-linking the final binary. It adds to MemoryManager a new member
function allowStubAllocation to control whether this MemoryManager
supports increasing code size with stubs or not. Since BOLT can
rewrite some files in-place, it needs to avoid stub insertion done
by the linker. This patch also introduces allowsZeroSymbols to the
JITSymbolResolver class, enabling us to finish a link successfully
even when some symbols resolve to the value zero. When rewriting a
binary, sometimes we do need to resolve a target to zero in case
the input binary calls address zero and we want to be bug
compatible. We also expose reassignSectionAddress as it is used by
BOLT.

Reviewed By: lhames

Differential Revision: https://reviews.llvm.org/D97898