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[lld-macho] If export_size is zero, export_off must be zero

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Otherwise tools like codesign_allocate will choke. We were already
handling this correctly for the other DYLD_INFO sections.

Doing this correctly is a bit subtle: we don't know if export_size will
be zero until we have run `ExportSection::finalizeContents()`. However,
we must still add the ExportSection to the `__LINKEDIT` segment in order
that it gets sorted during `sortSectionsAndSegments()`.

Reviewed By: #lld-macho, oontvoo

Differential Revision: https://reviews.llvm.org/D112589
This commit is contained in:
Jez Ng 2021-10-27 14:58:15 -04:00
parent 665060ea45
commit b7e12ca7aa
3 changed files with 12 additions and 5 deletions
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1
lld/MachO/SyntheticSections.h
View File

@ -345,6 +345,7 @@ public:
ExportSection();
void finalizeContents() override;
uint64_t getRawSize() const override { return size; }
bool isNeeded() const override { return size; }
void writeTo(uint8_t *buf) const override;
bool hasWeakSymbol = false;

7
lld/MachO/Writer.cpp
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@ -968,7 +968,12 @@ template <class LP> void Writer::createOutputSections() {
for (SyntheticSection *ssec : syntheticSections) {
auto it = concatOutputSections.find({ssec->segname, ssec->name});
if (ssec->isNeeded()) {
// We add all LinkEdit sections here because we don't know if they are
// needed until their finalizeContents() methods get called later. While
// this means that we add some redundant sections to __LINKEDIT, there is
// is no redundancy in the output, as we do not emit section headers for
// any LinkEdit sections.
if (ssec->isNeeded() || ssec->segname == segment_names::linkEdit) {
if (it == concatOutputSections.end()) {
getOrCreateOutputSegment(ssec->segname)->addOutputSection(ssec);
} else {

9
lld/test/MachO/no-unneeded-dyld-info.s
View File

@ -1,6 +1,6 @@
# REQUIRES: x86
# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %s -o %t.o
# RUN: %lld -o %t %t.o
# RUN: %lld -dylib -o %t %t.o
# RUN: llvm-objdump --macho --all-headers %t | FileCheck %s
# CHECK: cmd LC_DYLD_INFO_ONLY
@ -13,7 +13,8 @@
# CHECK-NEXT: weak_bind_size 0
# CHECK-NEXT: lazy_bind_off 0
# CHECK-NEXT: lazy_bind_size 0
# CHECK-NEXT: export_off 0
# CHECK-NEXT: export_size 0
.globl _main
_main:
ret
_not_exported:
.space 1