Commit Graph

4 Commits

Author SHA1 Message Date
Jez Ng abd70fb398 [lld-macho] Export trie addresses should be relative to the image base
We didn't notice this earlier this we were only testing the export trie
encoded in a dylib, whose image base starts at zero. But a regular
executable contains `__PAGEZERO`, which means it has a non-zero image
base. This bug was discovered after attempting to run some programs that
performed `dlopen` on an executable.

Reviewed By: #lld-macho, smeenai

Differential Revision: https://reviews.llvm.org/D87780
2020-09-20 20:43:15 -07:00
Jez Ng 7bbdbacd00 [lld-macho] Use export trie instead of symtab when linking against dylibs
Summary:
This allows us to link against stripped dylibs. Moreover, it's simply
more correct: The symbol table includes symbols that the dylib uses but
doesn't export.

This temporarily regresses our ability to do lazy symbol binding because
dyld_stub_binder isn't in libSystem's export trie. Rather, it is in one
of the sub-libraries libSystem re-exports. (This doesn't affect our
tests since we are mocking out dyld_stub_binder there.) A follow-up diff
will address this by adding support for sub-libraries.

Depends on D79114.

Reviewers: ruiu, pcc, MaskRay, smeenai, alexshap, gkm, Ktwu, christylee

Subscribers: mgorny, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D79226
2020-05-09 20:56:22 -07:00
Kellie Medlin 6cb073133c [lld] Merge Mach-O input sections
Summary: Similar to other formats, input sections in the MachO
implementation are now grouped under output sections. This is primarily
a refactor, although there's some new logic (like resolving the output
section's flags based on its inputs).

Differential Revision: https://reviews.llvm.org/D77893
2020-05-01 16:57:18 -07:00
Jez Ng 9854edd817 [lld-macho] Implement basic export trie
Build the trie by performing a three-way radix quicksort: We start by
sorting the strings by their first characters, then sort the strings
with the same first characters by their second characters, and so on
recursively. Each time the prefixes diverge, we add a node to the trie.
Thanks to @ruiu for the idea.

I used llvm-mc's radix quicksort implementation as a starting point. The
trie offset fixpoint code was taken from
MachONormalizedFileBinaryWriter.cpp.

Differential Revision: https://reviews.llvm.org/D76977
2020-04-29 15:44:27 -07:00