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[lld/mac] Test zerofill sections after __thread_bss 

Real zerofill sections go after __thread_bss, since zerofill sections
must all be at the end of their segment and __thread_bss must be right
after __thread_data.

Works fine already, but wasn't tested as far as I can tell.

Also tweak comment about zerofill sections a bit.

No behavior change.

Differential Revision: https://reviews.llvm.org/D104609
This commit is contained in:
Nico Weber 2021-06-20 19:39:09 -04:00
parent 62ed024c74
commit e6cb55d5ce
2 changed files with 29 additions and 3 deletions
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6
lld/MachO/OutputSegment.cpp
View File

@ -130,8 +130,10 @@ static int sectionOrder(OutputSection *osec) {
.Case(section_names::codeSignature, std::numeric_limits<int>::max())
.Default(osec->inputOrder);
}
// ZeroFill sections must always be the at the end of their segments,
// otherwise subsequent sections may get overwritten with zeroes at runtime.
// ZeroFill sections must always be the at the end of their segments:
// dyld checks if a segment's file size is smaller than its in-memory
// size to detect if a segment has zerofill sections, and if so it maps
// the missing tail as zerofill.
if (sectionType(osec->flags) == S_ZEROFILL)
return std::numeric_limits<int>::max();
return osec->inputOrder;

26
lld/test/MachO/tlv-dylib.s
View File

@ -69,11 +69,29 @@
# FLAGS-NEXT: segname __DATA
# FLAGS-NEXT: addr
# FLAGS-NEXT: size 0x0000000000000008
# FLAGS-NEXT: offset
# FLAGS-NEXT: offset 0
# FLAGS-NEXT: align 2^3 (8)
# FLAGS-NEXT: reloff 0
# FLAGS-NEXT: nreloc 0
# FLAGS-NEXT: type S_THREAD_LOCAL_ZEROFILL
# FLAGS: sectname __bss
# FLAGS-NEXT: segname __DATA
# FLAGS-NEXT: addr
# FLAGS-NEXT: size 0x0000000000002000
# FLAGS-NEXT: offset 0
# FLAGS-NEXT: align 2^0 (1)
# FLAGS-NEXT: reloff 0
# FLAGS-NEXT: nreloc 0
# FLAGS-NEXT: type S_ZEROFILL
# FLAGS: sectname __common
# FLAGS-NEXT: segname __DATA
# FLAGS-NEXT: addr
# FLAGS-NEXT: size 0x0000000000004000
# FLAGS-NEXT: offset 0
# FLAGS-NEXT: align 2^14 (16384)
# FLAGS-NEXT: reloff 0
# FLAGS-NEXT: nreloc 0
# FLAGS-NEXT: type S_ZEROFILL
#--- libtlv.s
.section __DATA,__thread_vars,thread_local_variables
@ -95,6 +113,12 @@ _main:
## Add some TLVs to test too, so that we can test the ordering
## of __thread_ptrs, __thread_data, and __thread_bss.
## Also add a .bss and a .comm for good measure too. Since they
## are both zerofill, they end up after __thread_bss.
.comm _com, 0x4000
.bss
.zero 0x2000
.section __DATA,__thread_data,thread_local_regular
_tfoo$tlv$init:
.quad 123