[X86] Fix R_X86_64_TPOFF32 against weak undefined TLS symbols - #1646
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[X86] Fix R_X86_64_TPOFF32 against weak undefined TLS symbols#1646Rachit Mehta (rachitmeht) wants to merge 1 commit into
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Rachit Mehta (rachitmeht)
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Parth (parth-07) and
Shankar Easwaran (quic-seaswara)
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August 6, 2026 09:14
Shankar Easwaran (quic-seaswara)
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Aug 7, 2026
| // be 0 instead of 1 (true). | ||
| if (!pSymbol->hasFragRef()) | ||
| return true; | ||
| return false; |
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This should be a seperate change.
| (pParent.config().codeGenType() == LinkerConfig::Exec)) { | ||
| Relocator::DWord A = pReloc.addend(); | ||
| return ApplyReloc(pReloc, A, pRelocDesc, DiagEngine, options, pParent); | ||
| } |
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What about shared/pie ?
what is the difference for other targets ?
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TPOFF handling for Weak undef is not done for other architectures also.
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I copied the check from relocAbs(), it mentions that weak-undef symbol resolving to 0 is only the correct link-time behavior in a static executable. So, for a shared/PIE, an unresolved symbol should be handled via dynamic relocations.
| # Case 6: TPOFF32 + weak-undef + addend=2 -> 0x00000002 | ||
| RUN: %clang %clangopts -c %p/Inputs/weak_tls_le_addend.s -o %t.addend.o | ||
| RUN: %link %linkopts -static %t.addend.o -o %t.addend.exe | ||
| RUN: llvm-objdump -s -j .data %t.addend.exe | FileCheck %s --check-prefix=ADDEND |
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%objdump
A weak undefined TLS symbol has no slot in the PT_TLS segment, so the thread-pointer-offset formula (S - templateSize) is meaningless for it. Previously relocTPOFF applied that formula with a bogus symbol value, producing an incorrect tpoff (e.g. -3) instead of the correct 0. Fix: add a weak-undef guard in relocTPOFF mirroring lld's R_TPREL handling (if (sym.isUndefined()) return a) and the existing guard in relocAbs (line 638). Add x86_64/linux/WeakUndefTLS covering TPOFF32/64 and DTPOFF32/64 against weak-undef symbols, a defined-symbol regression guard, and a non-zero addend case. Resolves qualcomm#1540 Signed-off-by: Rachit Mehta <rachmeht@qti.qualcomm.com>
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A weak undefined TLS symbol has no slot in the PT_TLS segment, so the thread-pointer-offset formula (S - templateSize) is meaningless for it. Previously relocTPOFF applied that formula with a bogus symbol value, producing an incorrect tpoff (e.g. -3) instead of the correct 0.
Two fixes, comparing lld's R_TPREL handling:
Add x86_64/linux/WeakUndefTLS covering TPOFF32/64 and DTPOFF32/64 against weak-undef symbols, a defined-symbol regression guard, and a non-zero addend case.
Resolves #1540