[llvm] r228939 - On ELF, put PIC jump tables in a non executable section.
Anna Zaks
ganna at apple.com
Fri Feb 13 14:56:42 PST 2015
Rafael,
This commit is causing a lot of ASan Unit test failures on darwin:
http://lab.llvm.org:8080/green/view/All/job/clang-stage1-cmake-RA_check/1487/console <http://lab.llvm.org:8080/green/view/All/job/clang-stage1-cmake-RA_check/1487/console>
Some are failing with EXC_I386_GPFLT some with EXC_BAD_ACCESS.
Please, revert.
Thank you,
Anna.
> On Feb 12, 2015, at 9:46 AM, Rafael Espindola <rafael.espindola at gmail.com> wrote:
>
> Author: rafael
> Date: Thu Feb 12 11:46:49 2015
> New Revision: 228939
>
> URL: http://llvm.org/viewvc/llvm-project?rev=228939&view=rev
> Log:
> On ELF, put PIC jump tables in a non executable section.
>
> Fixes PR22558.
>
> Modified:
> llvm/trunk/include/llvm/CodeGen/TargetLoweringObjectFileImpl.h
> llvm/trunk/include/llvm/Target/TargetLoweringObjectFile.h
> llvm/trunk/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
> llvm/trunk/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
> llvm/trunk/lib/Target/TargetLoweringObjectFile.cpp
> llvm/trunk/test/CodeGen/X86/global-sections.ll
>
> Modified: llvm/trunk/include/llvm/CodeGen/TargetLoweringObjectFileImpl.h
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/CodeGen/TargetLoweringObjectFileImpl.h?rev=228939&r1=228938&r2=228939&view=diff
> ==============================================================================
> --- llvm/trunk/include/llvm/CodeGen/TargetLoweringObjectFileImpl.h (original)
> +++ llvm/trunk/include/llvm/CodeGen/TargetLoweringObjectFileImpl.h Thu Feb 12 11:46:49 2015
> @@ -60,6 +60,9 @@ public:
> getSectionForJumpTable(const Function &F, Mangler &Mang,
> const TargetMachine &TM) const override;
>
> + bool shouldPutJumpTableInFunctionSection(bool UsesLabelDifference,
> + const Function &F) const override;
> +
> /// Return an MCExpr to use for a reference to the specified type info global
> /// variable from exception handling information.
> const MCExpr *
>
> Modified: llvm/trunk/include/llvm/Target/TargetLoweringObjectFile.h
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Target/TargetLoweringObjectFile.h?rev=228939&r1=228938&r2=228939&view=diff
> ==============================================================================
> --- llvm/trunk/include/llvm/Target/TargetLoweringObjectFile.h (original)
> +++ llvm/trunk/include/llvm/Target/TargetLoweringObjectFile.h Thu Feb 12 11:46:49 2015
> @@ -98,6 +98,9 @@ public:
> getSectionForJumpTable(const Function &F, Mangler &Mang,
> const TargetMachine &TM) const;
>
> + virtual bool shouldPutJumpTableInFunctionSection(bool UsesLabelDifference,
> + const Function &F) const;
> +
> /// Targets should implement this method to assign a section to globals with
> /// an explicit section specfied. The implementation of this method can
> /// assume that GV->hasSection() is true.
>
> Modified: llvm/trunk/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/AsmPrinter.cpp?rev=228939&r1=228938&r2=228939&view=diff
> ==============================================================================
> --- llvm/trunk/lib/CodeGen/AsmPrinter/AsmPrinter.cpp (original)
> +++ llvm/trunk/lib/CodeGen/AsmPrinter/AsmPrinter.cpp Thu Feb 12 11:46:49 2015
> @@ -1178,23 +1178,14 @@ void AsmPrinter::EmitJumpTableInfo() {
> // the appropriate section.
> const Function *F = MF->getFunction();
> const TargetLoweringObjectFile &TLOF = getObjFileLowering();
> - bool JTInDiffSection = false;
> - if (// In PIC mode, we need to emit the jump table to the same section as the
> - // function body itself, otherwise the label differences won't make sense.
> - // FIXME: Need a better predicate for this: what about custom entries?
> - MJTI->getEntryKind() == MachineJumpTableInfo::EK_LabelDifference32 ||
> - // We should also do if the section name is NULL or function is declared
> - // in discardable section
> - // FIXME: this isn't the right predicate, should be based on the MCSection
> - // for the function.
> - F->isWeakForLinker()) {
> - OutStreamer.SwitchSection(TLOF.SectionForGlobal(F, *Mang, TM));
> - } else {
> + bool JTInDiffSection = !TLOF.shouldPutJumpTableInFunctionSection(
> + MJTI->getEntryKind() == MachineJumpTableInfo::EK_LabelDifference32,
> + *F);
> + if (JTInDiffSection) {
> // Otherwise, drop it in the readonly section.
> const MCSection *ReadOnlySection =
> TLOF.getSectionForJumpTable(*F, *Mang, TM);
> OutStreamer.SwitchSection(ReadOnlySection);
> - JTInDiffSection = true;
> }
>
> EmitAlignment(Log2_32(
>
> Modified: llvm/trunk/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/TargetLoweringObjectFileImpl.cpp?rev=228939&r1=228938&r2=228939&view=diff
> ==============================================================================
> --- llvm/trunk/lib/CodeGen/TargetLoweringObjectFileImpl.cpp (original)
> +++ llvm/trunk/lib/CodeGen/TargetLoweringObjectFileImpl.cpp Thu Feb 12 11:46:49 2015
> @@ -356,6 +356,13 @@ const MCSection *TargetLoweringObjectFil
> return getContext().getELFSection(Name, ELF::SHT_PROGBITS, Flags, 0, Group);
> }
>
> +bool TargetLoweringObjectFileELF::shouldPutJumpTableInFunctionSection(
> + bool UsesLabelDifference, const Function &F) const {
> + // We can always create relative relocations, so use another section
> + // that can be marked non-executable.
> + return false;
> +}
> +
> /// getSectionForConstant - Given a mergeable constant with the
> /// specified size and relocation information, return a section that it
> /// should be placed in.
>
> Modified: llvm/trunk/lib/Target/TargetLoweringObjectFile.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/TargetLoweringObjectFile.cpp?rev=228939&r1=228938&r2=228939&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Target/TargetLoweringObjectFile.cpp (original)
> +++ llvm/trunk/lib/Target/TargetLoweringObjectFile.cpp Thu Feb 12 11:46:49 2015
> @@ -275,6 +275,24 @@ const MCSection *TargetLoweringObjectFil
> return getSectionForConstant(SectionKind::getReadOnly(), /*C=*/nullptr);
> }
>
> +bool TargetLoweringObjectFile::shouldPutJumpTableInFunctionSection(
> + bool UsesLabelDifference, const Function &F) const {
> + // In PIC mode, we need to emit the jump table to the same section as the
> + // function body itself, otherwise the label differences won't make sense.
> + // FIXME: Need a better predicate for this: what about custom entries?
> + if (UsesLabelDifference)
> + return true;
> +
> + // We should also do if the section name is NULL or function is declared
> + // in discardable section
> + // FIXME: this isn't the right predicate, should be based on the MCSection
> + // for the function.
> + if (F.isWeakForLinker())
> + return true;
> +
> + return false;
> +}
> +
> /// getSectionForConstant - Given a mergable constant with the
> /// specified size and relocation information, return a section that it
> /// should be placed in.
>
> Modified: llvm/trunk/test/CodeGen/X86/global-sections.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/global-sections.ll?rev=228939&r1=228938&r2=228939&view=diff
> ==============================================================================
> --- llvm/trunk/test/CodeGen/X86/global-sections.ll (original)
> +++ llvm/trunk/test/CodeGen/X86/global-sections.ll Thu Feb 12 11:46:49 2015
> @@ -3,6 +3,7 @@
> ; RUN: llc < %s -mtriple=i386-apple-darwin10 -relocation-model=static | FileCheck %s -check-prefix=DARWIN-STATIC
> ; RUN: llc < %s -mtriple=x86_64-apple-darwin10 | FileCheck %s -check-prefix=DARWIN64
> ; RUN: llc < %s -mtriple=i386-unknown-linux-gnu -data-sections -function-sections | FileCheck %s -check-prefix=LINUX-SECTIONS
> +; RUN: llc < %s -mtriple=x86_64-pc-linux -data-sections -function-sections -relocation-model=pic | FileCheck %s -check-prefix=LINUX-SECTIONS-PIC
> ; RUN: llc < %s -mtriple=i686-pc-win32 -data-sections -function-sections | FileCheck %s -check-prefix=WIN32-SECTIONS
>
> define void @F1() {
> @@ -41,6 +42,11 @@ bb5:
> ; LINUX-SECTIONS-NEXT: .cfi_endproc
> ; LINUX-SECTIONS-NEXT: .section .rodata.F2,"a", at progbits
>
> +; LINUX-SECTIONS-PIC: .section .text.F2,"ax", at progbits
> +; LINUX-SECTIONS-PIC: .size F2,
> +; LINUX-SECTIONS-PIC-NEXT: .cfi_endproc
> +; LINUX-SECTIONS-PIC-NEXT: .section .rodata.F2,"a", at progbits
> +
> ; int G1;
> @G1 = common global i32 0
>
>
>
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