Skip to content

[BPF] Report an warning if certain insn imm operand cannot fit in 32bit #142989

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 1 commit into from
Jun 13, 2025
Merged

[BPF] Report an warning if certain insn imm operand cannot fit in 32bit #142989

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
22 changes: 16 additions & 6 deletions llvm/lib/Target/BPF/MCTargetDesc/BPFMCCodeEmitter.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,7 @@
#include "MCTargetDesc/BPFMCTargetDesc.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/MC/MCCodeEmitter.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCFixup.h"
#include "llvm/MC/MCInst.h"
Expand All @@ -33,11 +34,12 @@ namespace {
class BPFMCCodeEmitter : public MCCodeEmitter {
const MCRegisterInfo &MRI;
bool IsLittleEndian;
MCContext &Ctx;

public:
BPFMCCodeEmitter(const MCInstrInfo &, const MCRegisterInfo &mri,
bool IsLittleEndian)
: MRI(mri), IsLittleEndian(IsLittleEndian) { }
bool IsLittleEndian, MCContext &ctx)
: MRI(mri), IsLittleEndian(IsLittleEndian), Ctx(ctx) {}
BPFMCCodeEmitter(const BPFMCCodeEmitter &) = delete;
void operator=(const BPFMCCodeEmitter &) = delete;
~BPFMCCodeEmitter() override = default;
Expand Down Expand Up @@ -67,12 +69,12 @@ class BPFMCCodeEmitter : public MCCodeEmitter {

MCCodeEmitter *llvm::createBPFMCCodeEmitter(const MCInstrInfo &MCII,
MCContext &Ctx) {
return new BPFMCCodeEmitter(MCII, *Ctx.getRegisterInfo(), true);
return new BPFMCCodeEmitter(MCII, *Ctx.getRegisterInfo(), true, Ctx);
}

MCCodeEmitter *llvm::createBPFbeMCCodeEmitter(const MCInstrInfo &MCII,
MCContext &Ctx) {
return new BPFMCCodeEmitter(MCII, *Ctx.getRegisterInfo(), false);
return new BPFMCCodeEmitter(MCII, *Ctx.getRegisterInfo(), false, Ctx);
}

unsigned BPFMCCodeEmitter::getMachineOpValue(const MCInst &MI,
Expand All @@ -81,8 +83,16 @@ unsigned BPFMCCodeEmitter::getMachineOpValue(const MCInst &MI,
const MCSubtargetInfo &STI) const {
if (MO.isReg())
return MRI.getEncodingValue(MO.getReg());
if (MO.isImm())
return static_cast<unsigned>(MO.getImm());
if (MO.isImm()) {
uint64_t Imm = MO.getImm();
uint64_t High32Bits = Imm >> 32, High33Bits = Imm >> 31;
if (MI.getOpcode() != BPF::LD_imm64 && High32Bits != 0 &&
High33Bits != 0x1FFFFFFFFULL) {
Ctx.reportWarning(MI.getLoc(),
"immediate out of range, shall fit in 32 bits");
}
return static_cast<unsigned>(Imm);
}

assert(MO.isExpr());

Expand Down
15 changes: 15 additions & 0 deletions llvm/test/CodeGen/BPF/warn-cmp.ll
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,15 @@
; RUN: llc -mtriple=bpfel -filetype=obj < %s 2>&1 >/dev/null | FileCheck %s

; CHECK: warning: immediate out of range, shall fit in 32 bits
define dso_local void @test_1() naked {
tail call void asm sideeffect
"r1 = 40; if r1 == 0x1deadbeef goto +0; r0 = 0; exit;", "~{r0},~{r1}"()
unreachable
}

; CHECK: warning: immediate out of range, shall fit in 32 bits
define dso_local void @test_2() naked {
tail call void asm sideeffect
"r1 = 40; if r1 == 0xffffffff00000000 goto +0; r0 = 0; exit;", "~{r0},~{r1}"()
unreachable
}