csu: Find the main pointer through the GOT
ClosedPublic
Actions

Authored by andrew on May 20 2024, 11:59 AM.

Details

Reviewers

brooks
imp
emaste
jhb
jrtc27

Group Reviewers

arm64

Commits

rG71f04a360965: csu: Find the main pointer through the GOT
rG53120fbb6895: csu: Find the main pointer through the GOT

Summary

Use the Global Offset Table to find the location of main in crt1. With
lld the old code would point to main@plt, however ld.bfd fails to link
when main is in a shared library.

Fix this by using the GOT address to find main as it works with both
lld and bfd.

Diff Detail

Repository

rG FreeBSD src repository

Lint

Lint Not Applicable

Unit

Tests Not Applicable

Event Timeline

andrew requested review of this revision.May 20 2024, 11:59 AM

andrew created this revision.

andrew added a parent revision: D45258: stand/kboot: Fix the linker script OUTPUT_FORMAT.

andrew added a child revision: D45260: sys/sys: Fix __builtin_is_aligned fallback.

Harbormaster completed remote builds in B57773: Diff 138760.May 20 2024, 12:01 PM

jhb added a reviewer: jrtc27.May 20 2024, 5:23 PM

It surprises me that GNU ld doesn't want to create canonical PLTs, but avoiding them is reasonable; they are to functions what copy relocations are to data.

Putting main in a shared library sounds particularly cursed, but I guess it's not uncommon for testing frameworks. Presumably this is for libgtest_main.

This revision is now accepted and ready to land.May 20 2024, 5:32 PM

It was for something in the Google testing bits.

Closed by commit rG53120fbb6895: csu: Find the main pointer through the GOT (authored by andrew). · Explain WhyMay 22 2024, 8:33 AM

This revision was automatically updated to reflect the committed changes.

andrew added a commit: rG53120fbb6895: csu: Find the main pointer through the GOT.

andrew added a commit: rG71f04a360965: csu: Find the main pointer through the GOT.Jul 15 2024, 12:40 PM