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Recommit r348243 - "[llvm-mc] - Do not crash when referencing undefined debug sections."

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The patch triggered an unrelated msan issue: LayoutOrder variable was not initialized.
(http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux-fast/builds/26794/steps/check-llvm%20msan/logs/stdio)
It was fixed.

Original commit message:
MC has code that pre-creates few debug sections:
https://github.com/llvm-mirror/llvm/blob/master/lib/MC/MCObjectFileInfo.cpp#L396

If users code has a reference to such section but does not redefine it,
MC code currently asserts, because still thinks they are normally defined.

The patch fixes the issue.

Differential revision: https://reviews.llvm.org/D55173
----
Modified : /llvm/trunk/lib/MC/ELFObjectWriter.cpp
Added : /llvm/trunk/test/MC/ELF/undefined-debug.s

llvm-svn: 348349
This commit is contained in:
George Rimar 2018-12-05 10:43:58 +00:00
parent 83f8b69281
commit 15ca2a3b45
3 changed files with 20 additions and 1 deletions
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14
lib/MC/ELFObjectWriter.cpp
View File

@ -669,6 +669,20 @@ void ELFWriter::computeSymbolTable(
} else {
const MCSectionELF &Section =
static_cast<const MCSectionELF &>(Symbol.getSection());
// We may end up with a situation when section symbol is technically
// defined, but should not be. That happens because we explicitly
// pre-create few .debug_* sections to have accessors.
// And if these sections were not really defined in the code, but were
// referenced, we simply error out.
if (!Section.isRegistered()) {
assert(static_cast<const MCSymbolELF &>(Symbol).getType() ==
ELF::STT_SECTION);
Ctx.reportError(SMLoc(),
"Undefined section reference: " + Symbol.getName());
continue;
}
if (Mode == NonDwoOnly && isDwoSection(Section))
continue;
MSD.SectionIndex = SectionIndexMap.lookup(&Section);

2
lib/MC/MCFragment.cpp
View File

@ -238,7 +238,7 @@ MCFragment::~MCFragment() = default;
MCFragment::MCFragment(FragmentType Kind, bool HasInstructions,
MCSection *Parent)
: Kind(Kind), HasInstructions(HasInstructions), Parent(Parent),
Atom(nullptr), Offset(~UINT64_C(0)) {
Atom(nullptr), Offset(~UINT64_C(0)), LayoutOrder(0) {
if (Parent && !isDummy())
Parent->getFragmentList().push_back(this);
}

5
test/MC/ELF/undefined-debug.s Normal file
View File

@ -0,0 +1,5 @@
// RUN: not llvm-mc -filetype=obj -triple x86_64-pc-linux-gnu %s -o %t 2>&1 | FileCheck %s
// CHECK: error: Undefined section reference: .debug_pubnames
.section .foo,"",@progbits
.long .debug_pubnames