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release/21.x: [ELF] -r/--emit-relocs: Fix crash when processing .rela.text before .text (#156354) #159948

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Merged
merged 1 commit into from
Sep 23, 2025
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release/21.x: [ELF] -r/--emit-relocs: Fix crash when processing .rela.text before .text (#156354) #159948

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20 changes: 12 additions & 8 deletions lld/ELF/LinkerScript.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1021,10 +1021,6 @@ void LinkerScript::addOrphanSections() {
}
};

// For further --emit-reloc handling code we need target output section
// to be created before we create relocation output section, so we want
// to create target sections first. We do not want priority handling
// for synthetic sections because them are special.
size_t n = 0;
for (InputSectionBase *isec : ctx.inputSections) {
// Process InputSection and MergeInputSection.
Expand All @@ -1037,10 +1033,18 @@ void LinkerScript::addOrphanSections() {
if (ctx.arg.relocatable && (isec->flags & SHF_LINK_ORDER))
continue;

if (auto *sec = dyn_cast<InputSection>(isec))
if (InputSectionBase *rel = sec->getRelocatedSection())
if (auto *relIS = dyn_cast_or_null<InputSectionBase>(rel->parent))
add(relIS);
if (auto *sec = dyn_cast<InputSection>(isec)) {
if (InputSectionBase *relocated = sec->getRelocatedSection()) {
// For --emit-relocs and -r, ensure the output section for .text.foo
// is created before the output section for .rela.text.foo.
add(relocated);
// EhInputSection sections are not added to ctx.inputSections. If we see
// .rela.eh_frame, ensure the output section for the synthetic
// EhFrameSection is created first.
if (auto *p = dyn_cast_or_null<InputSectionBase>(relocated->parent))
add(p);
}
}
add(isec);
if (ctx.arg.relocatable)
for (InputSectionBase *depSec : isec->dependentSections)
Expand Down
31 changes: 31 additions & 0 deletions lld/test/ELF/linkerscript/orphan-relocation.s
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Original file line number Diff line number Diff line change
@@ -0,0 +1,31 @@
# REQUIRES: x86
## Test that orphan section placement can handle a relocatable link where
## the relocation section is seen before the relocated section.

# RUN: rm -rf %t && split-file %s %t && cd %t

# RUN: llvm-mc -filetype=obj -triple=x86_64 a.s -o a.o
## In a.ro, .rela.text precedes its relocated section.
# RUN: ld.lld -r a.o -T 1.lds -o a.ro
# RUN: llvm-readelf -S a.ro | FileCheck %s
# CHECK: .rela.text RELA
# CHECK-NEXT: .text PROGBITS

# RUN: llvm-objcopy --rename-section .text=.com.text --rename-section .rela.text=.rela.com.text a.ro a1.o

## Regression test for #156354 , where we added an orphan RELA section before its relocated section.
# RUN: ld.lld -r a1.o -o a1.ro
# RUN: llvm-readelf -S a1.ro | FileCheck %s --check-prefix=CHECK1
# CHECK1: .com.text PROGBITS
# CHECK1-NEXT: .rela.com.text RELA

#--- a.s
.globl foo
foo:
call foo

#--- 1.lds
SECTIONS {
.rela.text 0 : { *(.rela.text) }
.text 0 : { *(.text) }
}
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