From 0bc2d9b0c5efd53dcdd3368146aa83c5b04158f6 Mon Sep 17 00:00:00 2001 From: Simon Dardis Date: Wed, 21 Feb 2018 00:05:05 +0000 Subject: [PATCH] [mips] Spectre variant two mitigation for MIPSR2 This patch provides mitigation for CVE-2017-5715, Spectre variant two, which affects the P5600 and P6600. It provides the option -mindirect-jump=hazard, which instructs the LLVM backend to replace indirect branches with their hazard barrier variants. This option is accepted when targeting MIPS revision two or later. The migitation strategy suggested by MIPS for these processors is to use two hazard barrier instructions. 'jalr.hb' and 'jr.hb' are hazard barrier variants of the 'jalr' and 'jr' instructions respectively. These instructions impede the execution of instruction stream until architecturally defined hazards (changes to the instruction stream, privileged registers which may affect execution) are cleared. These instructions in MIPS' designs are not speculated past. These instructions are used with the option -mindirect-jump=hazard when branching indirectly and for indirect function calls. These instructions are defined by the MIPS32R2 ISA, so this mitigation method is not compatible with processors which implement an earlier revision of the MIPS ISA. Implementation note: I've opted to provide this as an -mindirect-jump={hazard,...} style option in case alternative mitigation methods are required for other implementations of the MIPS ISA in future, e.g. retpoline style solutions. Reviewers: atanasyan Differential Revision: https://reviews.llvm.org/D43487 llvm-svn: 325651 --- clang/include/clang/Basic/DiagnosticDriverKinds.td | 4 +++ clang/include/clang/Driver/Options.td | 3 ++ clang/lib/Basic/Targets/Mips.h | 6 +++- clang/lib/Driver/ToolChains/Arch/Mips.cpp | 39 ++++++++++++++++++++++ clang/lib/Driver/ToolChains/Arch/Mips.h | 1 + clang/test/Driver/mips-features.c | 6 ++++ clang/test/Driver/mips-indirect-branch.c | 23 +++++++++++++ 7 files changed, 81 insertions(+), 1 deletion(-) create mode 100644 clang/test/Driver/mips-indirect-branch.c diff --git a/clang/include/clang/Basic/DiagnosticDriverKinds.td b/clang/include/clang/Basic/DiagnosticDriverKinds.td index a4d35be..182136f 100644 --- a/clang/include/clang/Basic/DiagnosticDriverKinds.td +++ b/clang/include/clang/Basic/DiagnosticDriverKinds.td @@ -333,6 +333,10 @@ def warn_drv_unsupported_abicalls : Warning< "ignoring '-mabicalls' option as it cannot be used with " "non position-independent code and the N64 ABI">, InGroup; +def err_drv_unsupported_indirect_jump_opt : Error< + "'-mindirect-jump=%0' is unsupported with the '%1' architecture">; +def err_drv_unknown_indirect_jump_opt : Error< + "unknown '-mindirect-jump=' option '%0'">; def warn_drv_unable_to_find_directory_expected : Warning< "unable to find %0 directory, expected to be in '%1'">, diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td index edfb44c..94e0483 100644 --- a/clang/include/clang/Driver/Options.td +++ b/clang/include/clang/Driver/Options.td @@ -2022,6 +2022,9 @@ def mbranch_likely : Flag<["-"], "mbranch-likely">, Group, IgnoredGCCCompat; def mno_branch_likely : Flag<["-"], "mno-branch-likely">, Group, IgnoredGCCCompat; +def mindirect_jump_EQ : Joined<["-"], "mindirect-jump=">, + Group, + HelpText<"Change indirect jump instructions to inhibit speculation">; def mdsp : Flag<["-"], "mdsp">, Group; def mno_dsp : Flag<["-"], "mno-dsp">, Group; def mdspr2 : Flag<["-"], "mdspr2">, Group; diff --git a/clang/lib/Basic/Targets/Mips.h b/clang/lib/Basic/Targets/Mips.h index 69d1630..24f0186 100644 --- a/clang/lib/Basic/Targets/Mips.h +++ b/clang/lib/Basic/Targets/Mips.h @@ -54,6 +54,7 @@ class LLVM_LIBRARY_VISIBILITY MipsTargetInfo : public TargetInfo { enum DspRevEnum { NoDSP, DSP1, DSP2 } DspRev; bool HasMSA; bool DisableMadd4; + bool UseIndirectJumpHazard; protected: bool HasFP64; @@ -64,7 +65,8 @@ public: : TargetInfo(Triple), IsMips16(false), IsMicromips(false), IsNan2008(false), IsAbs2008(false), IsSingleFloat(false), IsNoABICalls(false), CanUseBSDABICalls(false), FloatABI(HardFloat), - DspRev(NoDSP), HasMSA(false), DisableMadd4(false), HasFP64(false) { + DspRev(NoDSP), HasMSA(false), DisableMadd4(false), + UseIndirectJumpHazard(false), HasFP64(false) { TheCXXABI.set(TargetCXXABI::GenericMIPS); setABI((getTriple().getArch() == llvm::Triple::mips || @@ -339,6 +341,8 @@ public: IsAbs2008 = false; else if (Feature == "+noabicalls") IsNoABICalls = true; + else if (Feature == "+use-indirect-jump-hazard") + UseIndirectJumpHazard = true; } setDataLayout(); diff --git a/clang/lib/Driver/ToolChains/Arch/Mips.cpp b/clang/lib/Driver/ToolChains/Arch/Mips.cpp index 61481a9..e72754d 100644 --- a/clang/lib/Driver/ToolChains/Arch/Mips.cpp +++ b/clang/lib/Driver/ToolChains/Arch/Mips.cpp @@ -343,6 +343,28 @@ void mips::getMIPSTargetFeatures(const Driver &D, const llvm::Triple &Triple, AddTargetFeature(Args, Features, options::OPT_mno_madd4, options::OPT_mmadd4, "nomadd4"); AddTargetFeature(Args, Features, options::OPT_mmt, options::OPT_mno_mt, "mt"); + + if (Arg *A = Args.getLastArg(options::OPT_mindirect_jump_EQ)) { + StringRef Val = StringRef(A->getValue()); + if (Val == "hazard") { + Arg *B = + Args.getLastArg(options::OPT_mmicromips, options::OPT_mno_micromips); + Arg *C = Args.getLastArg(options::OPT_mips16, options::OPT_mno_mips16); + + if (B && B->getOption().matches(options::OPT_mmicromips)) + D.Diag(diag::err_drv_unsupported_indirect_jump_opt) + << "hazard" << "micromips"; + else if (C && C->getOption().matches(options::OPT_mips16)) + D.Diag(diag::err_drv_unsupported_indirect_jump_opt) + << "hazard" << "mips16"; + else if (mips::supportsIndirectJumpHazardBarrier(CPUName)) + Features.push_back("+use-indirect-jump-hazard"); + else + D.Diag(diag::err_drv_unsupported_indirect_jump_opt) + << "hazard" << CPUName; + } else + D.Diag(diag::err_drv_unknown_indirect_jump_opt) << Val; + } } mips::IEEE754Standard mips::getIEEE754Standard(StringRef &CPU) { @@ -447,3 +469,20 @@ bool mips::shouldUseFPXX(const ArgList &Args, const llvm::Triple &Triple, return UseFPXX; } + +bool mips::supportsIndirectJumpHazardBarrier(StringRef &CPU) { + // Supporting the hazard barrier method of dealing with indirect + // jumps requires MIPSR2 support. + return llvm::StringSwitch(CPU) + .Case("mips32r2", true) + .Case("mips32r3", true) + .Case("mips32r5", true) + .Case("mips32r6", true) + .Case("mips64r2", true) + .Case("mips64r3", true) + .Case("mips64r5", true) + .Case("mips64r6", true) + .Case("octeon", true) + .Case("p5600", true) + .Default(false); +} diff --git a/clang/lib/Driver/ToolChains/Arch/Mips.h b/clang/lib/Driver/ToolChains/Arch/Mips.h index 89eea9a..7e90488 100644 --- a/clang/lib/Driver/ToolChains/Arch/Mips.h +++ b/clang/lib/Driver/ToolChains/Arch/Mips.h @@ -53,6 +53,7 @@ bool isFPXXDefault(const llvm::Triple &Triple, StringRef CPUName, bool shouldUseFPXX(const llvm::opt::ArgList &Args, const llvm::Triple &Triple, StringRef CPUName, StringRef ABIName, mips::FloatABI FloatABI); +bool supportsIndirectJumpHazardBarrier(StringRef &CPU); } // end namespace mips } // end namespace target diff --git a/clang/test/Driver/mips-features.c b/clang/test/Driver/mips-features.c index a9db0f1..d9bde7d 100644 --- a/clang/test/Driver/mips-features.c +++ b/clang/test/Driver/mips-features.c @@ -402,3 +402,9 @@ // RUN: %clang -target -mips-mti-linux-gnu -### -c %s -mno-branch-likely 2>&1 \ // RUN: | FileCheck --check-prefix=NO-BRANCH-LIKELY %s // NO-BRANCH-LIKELY: argument unused during compilation: '-mno-branch-likely' + +// -mindirect-jump=hazard +// RUN: %clang -target mips-unknown-linux-gnu -### -c %s \ +// RUN: -mindirect-jump=hazard 2>&1 \ +// RUN: | FileCheck --check-prefix=INDIRECT-BH %s +// INDIRECT-BH: "-target-feature" "+use-indirect-jump-hazard" diff --git a/clang/test/Driver/mips-indirect-branch.c b/clang/test/Driver/mips-indirect-branch.c new file mode 100644 index 0000000..64e85d5 --- /dev/null +++ b/clang/test/Driver/mips-indirect-branch.c @@ -0,0 +1,23 @@ +// REQUIRES: mips-registered-target +// -mindirect-jump=hazard -mips32 +// RUN: %clang -target mips-unknown-linux-gnu -mips32 -### -c %s \ +// RUN: -mindirect-jump=hazard 2>&1 | FileCheck %s --check-prefix=MIPS32 +// MIPS32: error: '-mindirect-jump=hazard' is unsupported with the 'mips32' architecture + +// -mindirect-jump=hazard -mmicromips +// RUN: %clang -target mips-unknown-linux-gnu -mmicromips -### -c %s \ +// RUN: -mindirect-jump=hazard 2>&1 | FileCheck %s --check-prefix=MICROMIPS +// MICROMIPS: error: '-mindirect-jump=hazard' is unsupported with the 'micromips' architecture + +// -mindirect-jump=hazard -mips16 +// RUN: %clang -target mips-unknown-linux-gnu -mips16 -### -c %s \ +// RUN: -mindirect-jump=hazard 2>&1 | FileCheck %s --check-prefix=MIPS16 +// MIPS16: error: '-mindirect-jump=hazard' is unsupported with the 'mips16' architecture + +// RUN: %clang -target mips-unknown-linux-gnu -### -c %s \ +// RUN: -mindirect-jump=retopline 2>&1 | FileCheck %s --check-prefix=RETOPLINE +// RETOPLINE: error: unknown '-mindirect-jump=' option 'retopline' + +// RUN: %clang -target mips-unknown-linux-gnu -### -mips32 -c %s \ +// RUN: -mindirect-jump=retopline 2>&1 | FileCheck %s --check-prefix=MIXED +// MIXED: error: unknown '-mindirect-jump=' option 'retopline' -- 2.7.4