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[lld-macho] Fix code section ordering in output binary #134010

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merged 1 commit into from
Apr 4, 2025
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[lld-macho] Fix code section ordering in output binary #134010

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32 changes: 22 additions & 10 deletions lld/MachO/OutputSegment.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -103,20 +103,32 @@ static int sectionOrder(OutputSection *osec) {
// be the section that determines whether we need thunks or not.
if (osec->name == section_names::text)
return -6;

// Prioritize specific section ordering based on our knowledge. This ensures
// that certain sections are placed in a particular order, even if they
// are also categorized as code sections. This explicit ordering takes
// precedence over the general code section ordering.
int knownPriority =
StringSwitch<int>(osec->name)
.Case(section_names::stubs, -4)
.Case(section_names::stubHelper, -3)
.Case(section_names::objcStubs, -2)
.Case(section_names::initOffsets, -1)
.Case(section_names::unwindInfo,
std::numeric_limits<int>::max() - 1)
.Case(section_names::ehFrame, std::numeric_limits<int>::max())
.Default(0);

if (knownPriority != 0)
return knownPriority;

// Ensure all code sections are contiguous with `__text` for thunk
// calculations.
if (sections::isCodeSection(osec->name, segment_names::text, osec->flags) &&
osec->name != section_names::stubHelper) {
if (sections::isCodeSection(osec->name, segment_names::text, osec->flags)) {
return -5;
}
return StringSwitch<int>(osec->name)
.Case(section_names::stubs, -4)
.Case(section_names::stubHelper, -3)
.Case(section_names::objcStubs, -2)
.Case(section_names::initOffsets, -1)
.Case(section_names::unwindInfo, std::numeric_limits<int>::max() - 1)
.Case(section_names::ehFrame, std::numeric_limits<int>::max())
.Default(osec->inputOrder);

return osec->inputOrder;
} else if (segname == segment_names::data ||
segname == segment_names::dataConst) {
// For each thread spawned, dyld will initialize its TLVs by copying the
Expand Down
28 changes: 18 additions & 10 deletions lld/test/MachO/arm64-objc-stubs.s
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Original file line number Diff line number Diff line change
@@ -1,22 +1,23 @@
# REQUIRES: aarch64

# RUN: llvm-mc -filetype=obj -triple=arm64-apple-darwin %s -o %t.o
# RUN: %lld -arch arm64 -lSystem -o %t.out %t.o
# RUN: %lld -arch arm64 -lSystem -o %t.out %t.o -U _external_func
# RUN: llvm-otool -vs __TEXT __objc_stubs %t.out | FileCheck %s
# RUN: %lld -arch arm64 -lSystem -o %t.out %t.o -dead_strip
# RUN: %lld -arch arm64 -lSystem -o %t.out %t.o -dead_strip -U _external_func
# RUN: llvm-otool -vs __TEXT __objc_stubs %t.out | FileCheck %s
# RUN: %lld -arch arm64 -lSystem -o %t.out %t.o -objc_stubs_fast
# RUN: %lld -arch arm64 -lSystem -o %t.out %t.o -objc_stubs_fast -U _external_func
# RUN: llvm-otool -vs __TEXT __objc_stubs %t.out | FileCheck %s
# RUN: llvm-otool -l %t.out | FileCheck %s --check-prefix=FASTALIGN
# RUN: %lld -arch arm64 -lSystem -o %t.out %t.o -objc_stubs_small
# RUN: %lld -arch arm64 -lSystem -o %t.out %t.o -objc_stubs_small -U _external_func
# RUN: llvm-otool -vs __TEXT __objc_stubs %t.out | FileCheck %s --check-prefix=SMALL
# RUN: llvm-otool -l %t.out | FileCheck %s --check-prefix=SMALLALIGN
# RUN: llvm-objdump --section-headers %t.out | FileCheck %s --check-prefix=SECTIONS

# CHECK: Contents of (__TEXT,__objc_stubs) section

# CHECK-NEXT: _objc_msgSend$foo:
# CHECK-NEXT: adrp x1, 8 ; 0x100008000
# CHECK-NEXT: ldr x1, [x1, #0x10]
# CHECK-NEXT: ldr x1, [x1, #0x18]
# CHECK-NEXT: adrp x16, 4 ; 0x100004000
# CHECK-NEXT: ldr x16, [x16]
# CHECK-NEXT: br x16
Expand All @@ -26,7 +27,7 @@

# CHECK-NEXT: _objc_msgSend$length:
# CHECK-NEXT: adrp x1, 8 ; 0x100008000
# CHECK-NEXT: ldr x1, [x1, #0x18]
# CHECK-NEXT: ldr x1, [x1, #0x20]
# CHECK-NEXT: adrp x16, 4 ; 0x100004000
# CHECK-NEXT: ldr x16, [x16]
# CHECK-NEXT: br x16
Expand All @@ -44,13 +45,13 @@
# FASTALIGN-NEXT: align 2^5 (32)

# SMALL: _objc_msgSend$foo:
# SMALL-NEXT: adrp x1, 4 ; 0x100004000
# SMALL-NEXT: ldr x1, [x1, #0x10]
# SMALL-NEXT: adrp x1, 8 ; 0x100008000
# SMALL-NEXT: ldr x1, [x1, #0x18]
# SMALL-NEXT: b

# SMALL-NEXT: _objc_msgSend$length:
# SMALL-NEXT: adrp x1, 4 ; 0x100004000
# SMALL-NEXT: ldr x1, [x1, #0x18]
# SMALL-NEXT: adrp x1, 8 ; 0x100008000
# SMALL-NEXT: ldr x1, [x1, #0x20]
# SMALL-NEXT: b

# SMALLALIGN: sectname __objc_stubs
Expand All @@ -60,6 +61,12 @@
# SMALLALIGN-NEXT: offset
# SMALLALIGN-NEXT: align 2^2 (4)

## Check correct section ordering
# SECTIONS: Sections:
# SECTIONS: __text
# SECTIONS: __stubs
# SECTIONS: __objc_stubs

.section __TEXT,__objc_methname,cstring_literals
lselref1:
.asciz "foo"
Expand All @@ -81,4 +88,5 @@ _main:
bl _objc_msgSend$length
bl _objc_msgSend$foo
bl _objc_msgSend$foo
bl _external_func
ret