2aacb56e83
This commit aims to support BPF arena kernel side [feature](https://lore.kernel.org/bpf/20240209040608.98927-1-alexei.starovoitov@gmail.com/): - arena is a memory region accessible from both BPF program and userspace; - base pointers for this memory region differ between kernel and user spaces; - `dst_reg = addr_space_cast(src_reg, dst_addr_space, src_addr_space)` translates src_reg, a pointer in src_addr_space to dst_reg, equivalent pointer in dst_addr_space, {src,dst}_addr_space are immediate constants; - number 0 is assigned to kernel address space; - number 1 is assigned to user address space. On the LLVM side, the goal is to make load and store operations on arena pointers "transparent" for BPF programs: - assume that pointers with non-zero address space are pointers to arena memory; - assume that arena is identified by address space number; - assume that address space zero corresponds to kernel address space; - assume that every BPF-side load or store from arena is done via pointer in user address space, thus convert base pointers using `addr_space_cast(src_reg, 0, 1)`; Only load, store, cmpxchg and atomicrmw IR instructions are handled by this transformation. For example, the following C code: ```c #define __as __attribute__((address_space(1))) void copy(int __as *from, int __as *to) { *to = *from; } ``` Compiled to the following IR: ```llvm define void @copy(ptr addrspace(1) %from, ptr addrspace(1) %to) { entry: %0 = load i32, ptr addrspace(1) %from, align 4 store i32 %0, ptr addrspace(1) %to, align 4 ret void } ``` Is transformed to: ```llvm %to2 = addrspacecast ptr addrspace(1) %to to ptr ;; ! %from1 = addrspacecast ptr addrspace(1) %from to ptr ;; ! %0 = load i32, ptr %from1, align 4, !tbaa !3 store i32 %0, ptr %to2, align 4, !tbaa !3 ret void ``` And compiled as: ```asm r2 = addr_space_cast(r2, 0, 1) r1 = addr_space_cast(r1, 0, 1) r1 = *(u32 *)(r1 + 0) *(u32 *)(r2 + 0) = r1 exit ``` Co-authored-by: Eduard Zingerman <eddyz87@gmail.com>
102 lines
3.1 KiB
C++
102 lines
3.1 KiB
C++
//===-- BPF.h - Top-level interface for BPF representation ------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_LIB_TARGET_BPF_BPF_H
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#define LLVM_LIB_TARGET_BPF_BPF_H
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#include "MCTargetDesc/BPFMCTargetDesc.h"
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#include "llvm/IR/Instructions.h"
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#include "llvm/IR/PassManager.h"
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#include "llvm/Pass.h"
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#include "llvm/Target/TargetMachine.h"
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namespace llvm {
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class BPFRegisterBankInfo;
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class BPFSubtarget;
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class BPFTargetMachine;
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class InstructionSelector;
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class PassRegistry;
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ModulePass *createBPFCheckAndAdjustIR();
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FunctionPass *createBPFISelDag(BPFTargetMachine &TM);
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FunctionPass *createBPFMISimplifyPatchablePass();
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FunctionPass *createBPFMIPeepholePass();
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FunctionPass *createBPFMIPreEmitPeepholePass();
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FunctionPass *createBPFMIPreEmitCheckingPass();
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InstructionSelector *createBPFInstructionSelector(const BPFTargetMachine &,
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const BPFSubtarget &,
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const BPFRegisterBankInfo &);
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void initializeBPFCheckAndAdjustIRPass(PassRegistry&);
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void initializeBPFDAGToDAGISelPass(PassRegistry &);
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void initializeBPFMIPeepholePass(PassRegistry &);
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void initializeBPFMIPreEmitCheckingPass(PassRegistry&);
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void initializeBPFMIPreEmitPeepholePass(PassRegistry &);
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void initializeBPFMISimplifyPatchablePass(PassRegistry &);
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class BPFAbstractMemberAccessPass
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: public PassInfoMixin<BPFAbstractMemberAccessPass> {
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BPFTargetMachine *TM;
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public:
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BPFAbstractMemberAccessPass(BPFTargetMachine *TM) : TM(TM) {}
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PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
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static bool isRequired() { return true; }
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};
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class BPFPreserveDITypePass : public PassInfoMixin<BPFPreserveDITypePass> {
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public:
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PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
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static bool isRequired() { return true; }
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};
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class BPFIRPeepholePass : public PassInfoMixin<BPFIRPeepholePass> {
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public:
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PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
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static bool isRequired() { return true; }
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};
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class BPFASpaceCastSimplifyPass
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: public PassInfoMixin<BPFASpaceCastSimplifyPass> {
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public:
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PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
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static bool isRequired() { return true; }
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};
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class BPFAdjustOptPass : public PassInfoMixin<BPFAdjustOptPass> {
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public:
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PreservedAnalyses run(Module &M, ModuleAnalysisManager &AM);
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};
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class BPFPreserveStaticOffsetPass
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: public PassInfoMixin<BPFPreserveStaticOffsetPass> {
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bool AllowPartial;
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public:
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BPFPreserveStaticOffsetPass(bool AllowPartial) : AllowPartial(AllowPartial) {}
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PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
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static bool isRequired() { return true; }
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static std::pair<GetElementPtrInst *, LoadInst *>
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reconstructLoad(CallInst *Call);
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static std::pair<GetElementPtrInst *, StoreInst *>
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reconstructStore(CallInst *Call);
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};
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} // namespace llvm
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#endif
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