[PATCH] D66658: [ELF] Align the first section of a PT_LOAD even if its type is SHT_NOBITS

[Fangrui Song via Phabricator via llvm-commits]

MaskRay created this revision.
MaskRay added reviewers: grimar, pcc, peter.smith, ruiu.
Herald added subscribers: llvm-commits, arichardson, emaste.
Herald added a reviewer: espindola.
Herald added a project: LLVM.

Reported at https://reviews.llvm.org/D64930#1642223

If the only section of a PT_LOAD is a SHT_NOBITS section (e.g. .bss), we
may not align its sh_offset. p_offset of the PT_LOAD will be set to
sh_offset, and we will get p_offset!=p_vaddr (mod p_align).  If such
executable is mapped by the Linux kernel, it will segfault.

After D64906 <https://reviews.llvm.org/D64906>, this may happen the non-linker script case.

The linker script case has had this issue for a long time.
This was fixed by rL321657 <https://reviews.llvm.org/rL321657> (but the test linkerscript/nobits-offset.s
failed to test a SHT_NOBITS section), but broken by rL345154 <https://reviews.llvm.org/rL345154>.


Repository:
  rLLD LLVM Linker

https://reviews.llvm.org/D66658

Files:
  ELF/Writer.cpp
  test/ELF/linkerscript/nobits-offset.s
  test/ELF/nobits-offset.s
  test/ELF/relocatable.s
  test/ELF/relocation-copy-align-common.s

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