[llvm] r342692 - bpf: check illegal usage of XADD insn return value
Yonghong Song via llvm-commits
llvm-commits at lists.llvm.org
Thu Sep 20 15:24:27 PDT 2018
Author: yhs
Date: Thu Sep 20 15:24:27 2018
New Revision: 342692
URL: http://llvm.org/viewvc/llvm-project?rev=342692&view=rev
Log:
bpf: check illegal usage of XADD insn return value
Currently, BPF has XADD (locked add) insn support and the
asm looks like:
lock *(u32 *)(r1 + 0) += r2
lock *(u64 *)(r1 + 0) += r2
The instruction itself does not have a return value.
At the source code level, users often use
__sync_fetch_and_add()
which eventually translates to XADD. The return value of
__sync_fetch_and_add() is supposed to be the old value
in the xadd memory location. Since BPF::XADD insn does not
support such a return value, this patch added a PreEmit
phase to check such a usage. If such an illegal usage
pattern is detected, a fatal error will be reported like
line 4: Invalid usage of the XADD return value
if compiled with -g, or
Invalid usage of the XADD return value
if compiled without -g.
Signed-off-by: Yonghong Song <yhs at fb.com>
Acked-by: Alexei Starovoitov <ast at kernel.org>
Added:
llvm/trunk/lib/Target/BPF/BPFMIChecking.cpp
llvm/trunk/test/CodeGen/BPF/xadd.ll
Modified:
llvm/trunk/lib/Target/BPF/BPF.h
llvm/trunk/lib/Target/BPF/BPFTargetMachine.cpp
llvm/trunk/lib/Target/BPF/CMakeLists.txt
Modified: llvm/trunk/lib/Target/BPF/BPF.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/BPF/BPF.h?rev=342692&r1=342691&r2=342692&view=diff
==============================================================================
--- llvm/trunk/lib/Target/BPF/BPF.h (original)
+++ llvm/trunk/lib/Target/BPF/BPF.h Thu Sep 20 15:24:27 2018
@@ -19,9 +19,11 @@ class BPFTargetMachine;
FunctionPass *createBPFISelDag(BPFTargetMachine &TM);
FunctionPass *createBPFMIPeepholePass();
FunctionPass *createBPFMIPreEmitPeepholePass();
+FunctionPass *createBPFMIPreEmitCheckingPass();
void initializeBPFMIPeepholePass(PassRegistry&);
void initializeBPFMIPreEmitPeepholePass(PassRegistry&);
+void initializeBPFMIPreEmitCheckingPass(PassRegistry&);
}
#endif
Added: llvm/trunk/lib/Target/BPF/BPFMIChecking.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/BPF/BPFMIChecking.cpp?rev=342692&view=auto
==============================================================================
--- llvm/trunk/lib/Target/BPF/BPFMIChecking.cpp (added)
+++ llvm/trunk/lib/Target/BPF/BPFMIChecking.cpp Thu Sep 20 15:24:27 2018
@@ -0,0 +1,96 @@
+//===-------------- BPFMIChecking.cpp - MI Checking Legality -------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass performs checking to signal errors for certain illegal usages at
+// MachineInstruction layer. Specially, the result of XADD{32,64} insn should
+// not be used. The pass is done at the PreEmit pass right before the
+// machine code is emitted at which point the register liveness information
+// is still available.
+//
+//===----------------------------------------------------------------------===//
+
+#include "BPF.h"
+#include "BPFInstrInfo.h"
+#include "BPFTargetMachine.h"
+#include "llvm/CodeGen/MachineInstrBuilder.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
+
+using namespace llvm;
+
+#define DEBUG_TYPE "bpf-mi-checking"
+
+namespace {
+
+struct BPFMIPreEmitChecking : public MachineFunctionPass {
+
+ static char ID;
+ MachineFunction *MF;
+ const TargetRegisterInfo *TRI;
+
+ BPFMIPreEmitChecking() : MachineFunctionPass(ID) {
+ initializeBPFMIPreEmitCheckingPass(*PassRegistry::getPassRegistry());
+ }
+
+private:
+ // Initialize class variables.
+ void initialize(MachineFunction &MFParm);
+
+ void checkingIllegalXADD(void);
+
+public:
+
+ // Main entry point for this pass.
+ bool runOnMachineFunction(MachineFunction &MF) override {
+ if (!skipFunction(MF.getFunction())) {
+ initialize(MF);
+ checkingIllegalXADD();
+ }
+ return false;
+ }
+};
+
+// Initialize class variables.
+void BPFMIPreEmitChecking::initialize(MachineFunction &MFParm) {
+ MF = &MFParm;
+ TRI = MF->getSubtarget<BPFSubtarget>().getRegisterInfo();
+ LLVM_DEBUG(dbgs() << "*** BPF PreEmit checking pass ***\n\n");
+}
+
+void BPFMIPreEmitChecking::checkingIllegalXADD(void) {
+ for (MachineBasicBlock &MBB : *MF) {
+ for (MachineInstr &MI : MBB) {
+ if (MI.getOpcode() != BPF::XADD32 && MI.getOpcode() != BPF::XADD64)
+ continue;
+
+ LLVM_DEBUG(MI.dump());
+ if (!MI.allDefsAreDead()) {
+ DebugLoc Empty;
+ const DebugLoc &DL = MI.getDebugLoc();
+ if (DL != Empty)
+ report_fatal_error("line " + std::to_string(DL.getLine()) +
+ ": Invalid usage of the XADD return value", false);
+ else
+ report_fatal_error("Invalid usage of the XADD return value", false);
+ }
+ }
+ }
+
+ return;
+}
+
+} // end default namespace
+
+INITIALIZE_PASS(BPFMIPreEmitChecking, "bpf-mi-pemit-checking",
+ "BPF PreEmit Checking", false, false)
+
+char BPFMIPreEmitChecking::ID = 0;
+FunctionPass* llvm::createBPFMIPreEmitCheckingPass()
+{
+ return new BPFMIPreEmitChecking();
+}
Modified: llvm/trunk/lib/Target/BPF/BPFTargetMachine.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/BPF/BPFTargetMachine.cpp?rev=342692&r1=342691&r2=342692&view=diff
==============================================================================
--- llvm/trunk/lib/Target/BPF/BPFTargetMachine.cpp (original)
+++ llvm/trunk/lib/Target/BPF/BPFTargetMachine.cpp Thu Sep 20 15:24:27 2018
@@ -115,6 +115,7 @@ void BPFPassConfig::addMachineSSAOptimiz
void BPFPassConfig::addPreEmitPass() {
const BPFSubtarget *Subtarget = getBPFTargetMachine().getSubtargetImpl();
+ addPass(createBPFMIPreEmitCheckingPass());
if (getOptLevel() != CodeGenOpt::None)
if (Subtarget->getHasAlu32() && !DisableMIPeephole)
addPass(createBPFMIPreEmitPeepholePass());
Modified: llvm/trunk/lib/Target/BPF/CMakeLists.txt
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/BPF/CMakeLists.txt?rev=342692&r1=342691&r2=342692&view=diff
==============================================================================
--- llvm/trunk/lib/Target/BPF/CMakeLists.txt (original)
+++ llvm/trunk/lib/Target/BPF/CMakeLists.txt Thu Sep 20 15:24:27 2018
@@ -24,6 +24,7 @@ add_llvm_target(BPFCodeGen
BPFSubtarget.cpp
BPFTargetMachine.cpp
BPFMIPeephole.cpp
+ BPFMIChecking.cpp
)
add_subdirectory(AsmParser)
Added: llvm/trunk/test/CodeGen/BPF/xadd.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/BPF/xadd.ll?rev=342692&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/BPF/xadd.ll (added)
+++ llvm/trunk/test/CodeGen/BPF/xadd.ll Thu Sep 20 15:24:27 2018
@@ -0,0 +1,59 @@
+; RUN: not llc -march=bpfel < %s 2>&1 | FileCheck %s
+; RUN: not llc -march=bpfeb < %s 2>&1 | FileCheck %s
+
+; This file is generated with the source command and source
+; $ clang -target bpf -O2 -g -S -emit-llvm t.c
+; $ cat t.c
+; int test(int *ptr) {
+; int r;
+; __sync_fetch_and_add(ptr, 4);
+; r = __sync_fetch_and_add(ptr, 6);
+; return r;
+; }
+
+; ModuleID = 't.c'
+source_filename = "t.c"
+target datalayout = "e-m:e-p:64:64-i64:64-n32:64-S128"
+target triple = "bpf"
+
+; Function Attrs: nounwind
+define dso_local i32 @test(i32* nocapture %ptr) local_unnamed_addr #0 !dbg !7 {
+entry:
+ call void @llvm.dbg.value(metadata i32* %ptr, metadata !13, metadata !DIExpression()), !dbg !15
+ %0 = atomicrmw add i32* %ptr, i32 4 seq_cst, !dbg !16
+ %1 = atomicrmw add i32* %ptr, i32 6 seq_cst, !dbg !17
+; CHECK: line 4: Invalid usage of the XADD return value
+ call void @llvm.dbg.value(metadata i32 %1, metadata !14, metadata !DIExpression()), !dbg !18
+ ret i32 %1, !dbg !19
+}
+
+; Function Attrs: nounwind readnone speculatable
+declare void @llvm.dbg.value(metadata, metadata, metadata) #1
+
+attributes #0 = { nounwind "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #1 = { nounwind readnone speculatable }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4, !5}
+!llvm.ident = !{!6}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 8.0.0 (trunk 342605) (llvm/trunk 342612)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, nameTableKind: None)
+!1 = !DIFile(filename: "t.c", directory: "/home/yhs/work/tests/llvm/sync/test1")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{i32 1, !"wchar_size", i32 4}
+!6 = !{!"clang version 8.0.0 (trunk 342605) (llvm/trunk 342612)"}
+!7 = distinct !DISubprogram(name: "test", scope: !1, file: !1, line: 1, type: !8, isLocal: false, isDefinition: true, scopeLine: 1, flags: DIFlagPrototyped, isOptimized: true, unit: !0, retainedNodes: !12)
+!8 = !DISubroutineType(types: !9)
+!9 = !{!10, !11}
+!10 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!11 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !10, size: 64)
+!12 = !{!13, !14}
+!13 = !DILocalVariable(name: "ptr", arg: 1, scope: !7, file: !1, line: 1, type: !11)
+!14 = !DILocalVariable(name: "r", scope: !7, file: !1, line: 2, type: !10)
+!15 = !DILocation(line: 1, column: 15, scope: !7)
+!16 = !DILocation(line: 3, column: 4, scope: !7)
+!17 = !DILocation(line: 4, column: 8, scope: !7)
+!18 = !DILocation(line: 2, column: 8, scope: !7)
+!19 = !DILocation(line: 5, column: 4, scope: !7)
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