commit 1513e508b96c98f7271a0204b17a252e8c680b18
author Ali Tamur <tamur@google.com> Tue Oct 02 20:30:22 2018 +0000
committer Ali Tamur <tamur@google.com> Tue Oct 02 20:30:22 2018 +0000
tree 5ba516e956ceb3afa112f8c266080ebae1168c02
parent 9a8c0e59b4edcbbb52ae9ecd6885015003908a5a

Introduce a flag to warn when ifunc symbols are used with text relocations.

Summary:
This patch adds a new flag, --warn-ifunc-textrel, to work around a glibc bug. When a code with ifunc symbols is used to produce an object file with text relocations, lld always succeeds. However, if that object file is linked using an old version of glibc, the resultant binary just crashes with segmentation fault when it is run (The bug is going to be corrected as of glibc 2.19).

Since there is no way to tell beforehand what library the object file will be linked against in the future, there does not seem to be a fool-proof way for lld to give an error only in cases where the binary will crash. So, with this change (dated 2018-09-25), lld starts to give a warning, contingent on a new command line flag that does not have a gnu counter part. The default value for --warn-ifunc-textrel is false, so lld behaviour will not change unless the user explicitly asks lld to give a warning. Users that link with a glibc library with version 2.19 or newer, or does not use ifunc symbols, or does not generate object files with text relocations do not need to take any action. Other users may consider to start passing warn-ifunc-textrel to lld to get early warnings.

Reviewers: ruiu, espindola

Reviewed By: ruiu

Subscribers: grimar, MaskRay, markj, emaste, arichardson, llvm-commits

Differential Revision: https://reviews.llvm.org/D52430

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@343628 91177308-0d34-0410-b5e6-96231b3b80d8