[ELF] Align the first section of a PT_LOAD even if its type is
SHT_NOBITS
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, 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 (but the test linkerscript/nobits-offset.s failed
to test a SHT_NOBITS section), but broken by rL345154.
Reviewed By: peter.smith
Differential Revision: https://reviews.llvm.org/D66658
Pull in r371013 from upstream lld trunk (by Rui Ueyama):
Align output segments correctly
Previously, segments were aligned according to their first section's
alignment requirements. That was not correct, but segments are also
aligned to a page boundary, and a page boundary is usually much
larger than a section alignment requirement, so no one noticed this
bug before.
Now, lld has --nmagic option which sets maxPageSize to 1 to
effectively disable page alignment, which reveals the issue.
Fixes https://bugs.llvm.org/show_bug.cgi?id=43212
Differential Revision: https://reviews.llvm.org/D67152
Together, these should ensure gpboot.out gets a correctly aligned offset
for its .rodata section, and fix "layout constraint violation" errors
from objcopy.
24ea14660b