[PATCH] D111717: [ELF] Avoid adding orphan sections to a less fit segment

Fri Oct 15 11:23:49 PDT 2021

MaskRay added a comment.

Adding an orphan before the (previously) first section of a segment can create unintended effects (say the user specifies output section address for the first section).
We have quite refined `RankFlags`. If the needle section `sec` mostly matches the first section but has a refined rank, it makes sense to ignore the additional bits in this case.

It may be useful to strengthen the test by leveraging non-PROGBITS and PROGBITS read-only sections (`RF_RODATA`).

Am I right that this makes our behavior closer to ld.bfd? If yes, this looks quite nice.

---

As of PT_GNU_RELRO, this may be another fallout of our default `-z relro`. We probably shouldn't change it now.
If a generic improvement like this patch makes the relro issue moot, that is certainly great.

================
Comment at: lld/test/ELF/linkerscript/orphan-phdrs2.test:12
+# CHECK:     LOAD {{.*}} R E
+# CHECK:     LOAD {{.*}} RW
+
----------------
CHECK-NEXT:

================
Comment at: lld/test/ELF/linkerscript/orphan-phdrs2.test:15
+# CHECK:     Segment Sections...
+# CHECK-NOT: 00{{.*}} .dynamic
+# CHECK:     01 .data .dynamic 
----------------
NOT is not needed. A positive CHECK exists.

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D111717/new/

https://reviews.llvm.org/D111717