From f4ca4a6fa147507ead2d10490af68c6adab898c8 Mon Sep 17 00:00:00 2001 From: George Rimar Date: Tue, 24 Oct 2017 08:26:32 +0000 Subject: [PATCH] [ELF] - Do not collect SHT_REL[A] sections unconditionally when --gc-sections and --emit-relocs used together. This is "Bug 34836 - --gc-sections remove relocations from --emit-relocs", When --emit-relocs is used, LLD currently always drops SHT_REL[A] sections from output if --gc-sections is present. Patch fixes the issue. Differential revision: https://reviews.llvm.org/D38724 llvm-svn: 316418 --- lld/ELF/InputSection.h | 4 ++-- lld/ELF/MarkLive.cpp | 12 +++--------- lld/test/ELF/emit-relocs-gc.s | 16 ++++++++++++++-- 3 files changed, 19 insertions(+), 13 deletions(-) diff --git a/lld/ELF/InputSection.h b/lld/ELF/InputSection.h index 4453da8..e36eb40 100644 --- a/lld/ELF/InputSection.h +++ b/lld/ELF/InputSection.h @@ -237,8 +237,8 @@ public: // Mark the piece at a given offset live. Used by GC. void markLiveAt(uint64_t Offset) { - assert(this->Flags & llvm::ELF::SHF_ALLOC); - LiveOffsets.insert(Offset); + if (this->Flags & llvm::ELF::SHF_ALLOC) + LiveOffsets.insert(Offset); } // Translate an offset in the input section to an offset diff --git a/lld/ELF/MarkLive.cpp b/lld/ELF/MarkLive.cpp index 62a0039..05fe3a4 100644 --- a/lld/ELF/MarkLive.cpp +++ b/lld/ELF/MarkLive.cpp @@ -162,9 +162,9 @@ scanEhFrameSection(EhInputSection &EH, scanEhFrameSection(EH, EH.template rels(), Fn); } -// We do not garbage-collect two types of sections: -// 1) Sections used by the loader (.init, .fini, .ctors, .dtors or .jcr) -// 2) Non-allocatable sections which typically contain debugging information +// Some sections are used directly by the loader, so they should never be +// garbage-collected. This function returns true if a given section is such +// section. template static bool isReserved(InputSectionBase *Sec) { switch (Sec->Type) { case SHT_FINI_ARRAY: @@ -173,9 +173,6 @@ template static bool isReserved(InputSectionBase *Sec) { case SHT_PREINIT_ARRAY: return true; default: - if (!(Sec->Flags & SHF_ALLOC)) - return true; - StringRef S = Sec->Name; return S.startswith(".ctors") || S.startswith(".dtors") || S.startswith(".init") || S.startswith(".fini") || @@ -198,9 +195,6 @@ template static void doGcSections() { if (Sec == &InputSection::Discarded) return; - // We don't gc non alloc sections. - if (!(Sec->Flags & SHF_ALLOC)) - return; // Usually, a whole section is marked as live or dead, but in mergeable // (splittable) sections, each piece of data has independent liveness bit. diff --git a/lld/test/ELF/emit-relocs-gc.s b/lld/test/ELF/emit-relocs-gc.s index 5b8bdfe..0741e78 100644 --- a/lld/test/ELF/emit-relocs-gc.s +++ b/lld/test/ELF/emit-relocs-gc.s @@ -1,18 +1,30 @@ # REQUIRES: x86 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t.o -## Show that we emit .rela.bar when GC is disabled. +## Show that we emit .rela.bar and .rela.text when GC is disabled. # RUN: ld.lld --emit-relocs %t.o -o %t # RUN: llvm-objdump %t -section-headers | FileCheck %s --check-prefix=NOGC +# NOGC: .rela.text # NOGC: .rela.bar -## GC collects .bar section and we exclude .rela.bar from output. +## GC collects .bar section and we exclude .rela.bar from output. We keep +## .rela.text because we keep .text. # RUN: ld.lld --gc-sections --emit-relocs --print-gc-sections %t.o -o %t \ # RUN: | FileCheck --check-prefix=MSG %s # MSG: removing unused section from '.bar' in file # MSG: removing unused section from '.rela.bar' in file # RUN: llvm-objdump %t -section-headers | FileCheck %s --check-prefix=GC # GC-NOT: rela.bar +# GC: rela.text +# GC-NOT: rela.bar .section .bar,"a" .quad .bar + +.text +relocs: +.quad _start + +.global _start +_start: + nop -- 2.7.4