File: | build/llvm-toolchain-snapshot-15~++20220420111733+e13d2efed663/llvm/lib/Target/BPF/BPFAbstractMemberAccess.cpp |
Warning: | line 801, column 5 Value stored to 'Call' is never read |
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1 | //===------ BPFAbstractMemberAccess.cpp - Abstracting Member Accesses -----===// |
2 | // |
3 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
4 | // See https://llvm.org/LICENSE.txt for license information. |
5 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
6 | // |
7 | //===----------------------------------------------------------------------===// |
8 | // |
9 | // This pass abstracted struct/union member accesses in order to support |
10 | // compile-once run-everywhere (CO-RE). The CO-RE intends to compile the program |
11 | // which can run on different kernels. In particular, if bpf program tries to |
12 | // access a particular kernel data structure member, the details of the |
13 | // intermediate member access will be remembered so bpf loader can do |
14 | // necessary adjustment right before program loading. |
15 | // |
16 | // For example, |
17 | // |
18 | // struct s { |
19 | // int a; |
20 | // int b; |
21 | // }; |
22 | // struct t { |
23 | // struct s c; |
24 | // int d; |
25 | // }; |
26 | // struct t e; |
27 | // |
28 | // For the member access e.c.b, the compiler will generate code |
29 | // &e + 4 |
30 | // |
31 | // The compile-once run-everywhere instead generates the following code |
32 | // r = 4 |
33 | // &e + r |
34 | // The "4" in "r = 4" can be changed based on a particular kernel version. |
35 | // For example, on a particular kernel version, if struct s is changed to |
36 | // |
37 | // struct s { |
38 | // int new_field; |
39 | // int a; |
40 | // int b; |
41 | // } |
42 | // |
43 | // By repeating the member access on the host, the bpf loader can |
44 | // adjust "r = 4" as "r = 8". |
45 | // |
46 | // This feature relies on the following three intrinsic calls: |
47 | // addr = preserve_array_access_index(base, dimension, index) |
48 | // addr = preserve_union_access_index(base, di_index) |
49 | // !llvm.preserve.access.index <union_ditype> |
50 | // addr = preserve_struct_access_index(base, gep_index, di_index) |
51 | // !llvm.preserve.access.index <struct_ditype> |
52 | // |
53 | // Bitfield member access needs special attention. User cannot take the |
54 | // address of a bitfield acceess. To facilitate kernel verifier |
55 | // for easy bitfield code optimization, a new clang intrinsic is introduced: |
56 | // uint32_t __builtin_preserve_field_info(member_access, info_kind) |
57 | // In IR, a chain with two (or more) intrinsic calls will be generated: |
58 | // ... |
59 | // addr = preserve_struct_access_index(base, 1, 1) !struct s |
60 | // uint32_t result = bpf_preserve_field_info(addr, info_kind) |
61 | // |
62 | // Suppose the info_kind is FIELD_SIGNEDNESS, |
63 | // The above two IR intrinsics will be replaced with |
64 | // a relocatable insn: |
65 | // signness = /* signness of member_access */ |
66 | // and signness can be changed by bpf loader based on the |
67 | // types on the host. |
68 | // |
69 | // User can also test whether a field exists or not with |
70 | // uint32_t result = bpf_preserve_field_info(member_access, FIELD_EXISTENCE) |
71 | // The field will be always available (result = 1) during initial |
72 | // compilation, but bpf loader can patch with the correct value |
73 | // on the target host where the member_access may or may not be available |
74 | // |
75 | //===----------------------------------------------------------------------===// |
76 | |
77 | #include "BPF.h" |
78 | #include "BPFCORE.h" |
79 | #include "BPFTargetMachine.h" |
80 | #include "llvm/BinaryFormat/Dwarf.h" |
81 | #include "llvm/IR/DebugInfoMetadata.h" |
82 | #include "llvm/IR/GlobalVariable.h" |
83 | #include "llvm/IR/Instruction.h" |
84 | #include "llvm/IR/Instructions.h" |
85 | #include "llvm/IR/IntrinsicsBPF.h" |
86 | #include "llvm/IR/Module.h" |
87 | #include "llvm/IR/PassManager.h" |
88 | #include "llvm/IR/Type.h" |
89 | #include "llvm/IR/User.h" |
90 | #include "llvm/IR/Value.h" |
91 | #include "llvm/Pass.h" |
92 | #include "llvm/Transforms/Utils/BasicBlockUtils.h" |
93 | #include <stack> |
94 | |
95 | #define DEBUG_TYPE"bpf-abstract-member-access" "bpf-abstract-member-access" |
96 | |
97 | namespace llvm { |
98 | constexpr StringRef BPFCoreSharedInfo::AmaAttr; |
99 | uint32_t BPFCoreSharedInfo::SeqNum; |
100 | |
101 | Instruction *BPFCoreSharedInfo::insertPassThrough(Module *M, BasicBlock *BB, |
102 | Instruction *Input, |
103 | Instruction *Before) { |
104 | Function *Fn = Intrinsic::getDeclaration( |
105 | M, Intrinsic::bpf_passthrough, {Input->getType(), Input->getType()}); |
106 | Constant *SeqNumVal = ConstantInt::get(Type::getInt32Ty(BB->getContext()), |
107 | BPFCoreSharedInfo::SeqNum++); |
108 | |
109 | auto *NewInst = CallInst::Create(Fn, {SeqNumVal, Input}); |
110 | BB->getInstList().insert(Before->getIterator(), NewInst); |
111 | return NewInst; |
112 | } |
113 | } // namespace llvm |
114 | |
115 | using namespace llvm; |
116 | |
117 | namespace { |
118 | class BPFAbstractMemberAccess final { |
119 | public: |
120 | BPFAbstractMemberAccess(BPFTargetMachine *TM) : TM(TM) {} |
121 | |
122 | bool run(Function &F); |
123 | |
124 | struct CallInfo { |
125 | uint32_t Kind; |
126 | uint32_t AccessIndex; |
127 | MaybeAlign RecordAlignment; |
128 | MDNode *Metadata; |
129 | Value *Base; |
130 | }; |
131 | typedef std::stack<std::pair<CallInst *, CallInfo>> CallInfoStack; |
132 | |
133 | private: |
134 | enum : uint32_t { |
135 | BPFPreserveArrayAI = 1, |
136 | BPFPreserveUnionAI = 2, |
137 | BPFPreserveStructAI = 3, |
138 | BPFPreserveFieldInfoAI = 4, |
139 | }; |
140 | |
141 | TargetMachine *TM; |
142 | const DataLayout *DL = nullptr; |
143 | Module *M = nullptr; |
144 | |
145 | static std::map<std::string, GlobalVariable *> GEPGlobals; |
146 | // A map to link preserve_*_access_index instrinsic calls. |
147 | std::map<CallInst *, std::pair<CallInst *, CallInfo>> AIChain; |
148 | // A map to hold all the base preserve_*_access_index instrinsic calls. |
149 | // The base call is not an input of any other preserve_* |
150 | // intrinsics. |
151 | std::map<CallInst *, CallInfo> BaseAICalls; |
152 | |
153 | bool doTransformation(Function &F); |
154 | |
155 | void traceAICall(CallInst *Call, CallInfo &ParentInfo); |
156 | void traceBitCast(BitCastInst *BitCast, CallInst *Parent, |
157 | CallInfo &ParentInfo); |
158 | void traceGEP(GetElementPtrInst *GEP, CallInst *Parent, |
159 | CallInfo &ParentInfo); |
160 | void collectAICallChains(Function &F); |
161 | |
162 | bool IsPreserveDIAccessIndexCall(const CallInst *Call, CallInfo &Cinfo); |
163 | bool IsValidAIChain(const MDNode *ParentMeta, uint32_t ParentAI, |
164 | const MDNode *ChildMeta); |
165 | bool removePreserveAccessIndexIntrinsic(Function &F); |
166 | void replaceWithGEP(std::vector<CallInst *> &CallList, |
167 | uint32_t NumOfZerosIndex, uint32_t DIIndex); |
168 | bool HasPreserveFieldInfoCall(CallInfoStack &CallStack); |
169 | void GetStorageBitRange(DIDerivedType *MemberTy, Align RecordAlignment, |
170 | uint32_t &StartBitOffset, uint32_t &EndBitOffset); |
171 | uint32_t GetFieldInfo(uint32_t InfoKind, DICompositeType *CTy, |
172 | uint32_t AccessIndex, uint32_t PatchImm, |
173 | MaybeAlign RecordAlignment); |
174 | |
175 | Value *computeBaseAndAccessKey(CallInst *Call, CallInfo &CInfo, |
176 | std::string &AccessKey, MDNode *&BaseMeta); |
177 | MDNode *computeAccessKey(CallInst *Call, CallInfo &CInfo, |
178 | std::string &AccessKey, bool &IsInt32Ret); |
179 | uint64_t getConstant(const Value *IndexValue); |
180 | bool transformGEPChain(CallInst *Call, CallInfo &CInfo); |
181 | }; |
182 | |
183 | std::map<std::string, GlobalVariable *> BPFAbstractMemberAccess::GEPGlobals; |
184 | |
185 | class BPFAbstractMemberAccessLegacyPass final : public FunctionPass { |
186 | BPFTargetMachine *TM; |
187 | |
188 | bool runOnFunction(Function &F) override { |
189 | return BPFAbstractMemberAccess(TM).run(F); |
190 | } |
191 | |
192 | public: |
193 | static char ID; |
194 | |
195 | // Add optional BPFTargetMachine parameter so that BPF backend can add the |
196 | // phase with target machine to find out the endianness. The default |
197 | // constructor (without parameters) is used by the pass manager for managing |
198 | // purposes. |
199 | BPFAbstractMemberAccessLegacyPass(BPFTargetMachine *TM = nullptr) |
200 | : FunctionPass(ID), TM(TM) {} |
201 | }; |
202 | |
203 | } // End anonymous namespace |
204 | |
205 | char BPFAbstractMemberAccessLegacyPass::ID = 0; |
206 | INITIALIZE_PASS(BPFAbstractMemberAccessLegacyPass, DEBUG_TYPE,static void *initializeBPFAbstractMemberAccessLegacyPassPassOnce (PassRegistry &Registry) { PassInfo *PI = new PassInfo( "BPF Abstract Member Access" , "bpf-abstract-member-access", &BPFAbstractMemberAccessLegacyPass ::ID, PassInfo::NormalCtor_t(callDefaultCtor<BPFAbstractMemberAccessLegacyPass >), false, false); Registry.registerPass(*PI, true); return PI; } static llvm::once_flag InitializeBPFAbstractMemberAccessLegacyPassPassFlag ; void llvm::initializeBPFAbstractMemberAccessLegacyPassPass( PassRegistry &Registry) { llvm::call_once(InitializeBPFAbstractMemberAccessLegacyPassPassFlag , initializeBPFAbstractMemberAccessLegacyPassPassOnce, std::ref (Registry)); } |
207 | "BPF Abstract Member Access", false, false)static void *initializeBPFAbstractMemberAccessLegacyPassPassOnce (PassRegistry &Registry) { PassInfo *PI = new PassInfo( "BPF Abstract Member Access" , "bpf-abstract-member-access", &BPFAbstractMemberAccessLegacyPass ::ID, PassInfo::NormalCtor_t(callDefaultCtor<BPFAbstractMemberAccessLegacyPass >), false, false); Registry.registerPass(*PI, true); return PI; } static llvm::once_flag InitializeBPFAbstractMemberAccessLegacyPassPassFlag ; void llvm::initializeBPFAbstractMemberAccessLegacyPassPass( PassRegistry &Registry) { llvm::call_once(InitializeBPFAbstractMemberAccessLegacyPassPassFlag , initializeBPFAbstractMemberAccessLegacyPassPassOnce, std::ref (Registry)); } |
208 | |
209 | FunctionPass *llvm::createBPFAbstractMemberAccess(BPFTargetMachine *TM) { |
210 | return new BPFAbstractMemberAccessLegacyPass(TM); |
211 | } |
212 | |
213 | bool BPFAbstractMemberAccess::run(Function &F) { |
214 | LLVM_DEBUG(dbgs() << "********** Abstract Member Accesses **********\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("bpf-abstract-member-access")) { dbgs() << "********** Abstract Member Accesses **********\n" ; } } while (false); |
215 | |
216 | M = F.getParent(); |
217 | if (!M) |
218 | return false; |
219 | |
220 | // Bail out if no debug info. |
221 | if (M->debug_compile_units().empty()) |
222 | return false; |
223 | |
224 | DL = &M->getDataLayout(); |
225 | return doTransformation(F); |
226 | } |
227 | |
228 | static bool SkipDIDerivedTag(unsigned Tag, bool skipTypedef) { |
229 | if (Tag != dwarf::DW_TAG_typedef && Tag != dwarf::DW_TAG_const_type && |
230 | Tag != dwarf::DW_TAG_volatile_type && |
231 | Tag != dwarf::DW_TAG_restrict_type && |
232 | Tag != dwarf::DW_TAG_member) |
233 | return false; |
234 | if (Tag == dwarf::DW_TAG_typedef && !skipTypedef) |
235 | return false; |
236 | return true; |
237 | } |
238 | |
239 | static DIType * stripQualifiers(DIType *Ty, bool skipTypedef = true) { |
240 | while (auto *DTy = dyn_cast<DIDerivedType>(Ty)) { |
241 | if (!SkipDIDerivedTag(DTy->getTag(), skipTypedef)) |
242 | break; |
243 | Ty = DTy->getBaseType(); |
244 | } |
245 | return Ty; |
246 | } |
247 | |
248 | static const DIType * stripQualifiers(const DIType *Ty) { |
249 | while (auto *DTy = dyn_cast<DIDerivedType>(Ty)) { |
250 | if (!SkipDIDerivedTag(DTy->getTag(), true)) |
251 | break; |
252 | Ty = DTy->getBaseType(); |
253 | } |
254 | return Ty; |
255 | } |
256 | |
257 | static uint32_t calcArraySize(const DICompositeType *CTy, uint32_t StartDim) { |
258 | DINodeArray Elements = CTy->getElements(); |
259 | uint32_t DimSize = 1; |
260 | for (uint32_t I = StartDim; I < Elements.size(); ++I) { |
261 | if (auto *Element = dyn_cast_or_null<DINode>(Elements[I])) |
262 | if (Element->getTag() == dwarf::DW_TAG_subrange_type) { |
263 | const DISubrange *SR = cast<DISubrange>(Element); |
264 | auto *CI = SR->getCount().dyn_cast<ConstantInt *>(); |
265 | DimSize *= CI->getSExtValue(); |
266 | } |
267 | } |
268 | |
269 | return DimSize; |
270 | } |
271 | |
272 | static Type *getBaseElementType(const CallInst *Call) { |
273 | // Element type is stored in an elementtype() attribute on the first param. |
274 | return Call->getParamElementType(0); |
275 | } |
276 | |
277 | /// Check whether a call is a preserve_*_access_index intrinsic call or not. |
278 | bool BPFAbstractMemberAccess::IsPreserveDIAccessIndexCall(const CallInst *Call, |
279 | CallInfo &CInfo) { |
280 | if (!Call) |
281 | return false; |
282 | |
283 | const auto *GV = dyn_cast<GlobalValue>(Call->getCalledOperand()); |
284 | if (!GV) |
285 | return false; |
286 | if (GV->getName().startswith("llvm.preserve.array.access.index")) { |
287 | CInfo.Kind = BPFPreserveArrayAI; |
288 | CInfo.Metadata = Call->getMetadata(LLVMContext::MD_preserve_access_index); |
289 | if (!CInfo.Metadata) |
290 | report_fatal_error("Missing metadata for llvm.preserve.array.access.index intrinsic"); |
291 | CInfo.AccessIndex = getConstant(Call->getArgOperand(2)); |
292 | CInfo.Base = Call->getArgOperand(0); |
293 | CInfo.RecordAlignment = DL->getABITypeAlign(getBaseElementType(Call)); |
294 | return true; |
295 | } |
296 | if (GV->getName().startswith("llvm.preserve.union.access.index")) { |
297 | CInfo.Kind = BPFPreserveUnionAI; |
298 | CInfo.Metadata = Call->getMetadata(LLVMContext::MD_preserve_access_index); |
299 | if (!CInfo.Metadata) |
300 | report_fatal_error("Missing metadata for llvm.preserve.union.access.index intrinsic"); |
301 | CInfo.AccessIndex = getConstant(Call->getArgOperand(1)); |
302 | CInfo.Base = Call->getArgOperand(0); |
303 | return true; |
304 | } |
305 | if (GV->getName().startswith("llvm.preserve.struct.access.index")) { |
306 | CInfo.Kind = BPFPreserveStructAI; |
307 | CInfo.Metadata = Call->getMetadata(LLVMContext::MD_preserve_access_index); |
308 | if (!CInfo.Metadata) |
309 | report_fatal_error("Missing metadata for llvm.preserve.struct.access.index intrinsic"); |
310 | CInfo.AccessIndex = getConstant(Call->getArgOperand(2)); |
311 | CInfo.Base = Call->getArgOperand(0); |
312 | CInfo.RecordAlignment = DL->getABITypeAlign(getBaseElementType(Call)); |
313 | return true; |
314 | } |
315 | if (GV->getName().startswith("llvm.bpf.preserve.field.info")) { |
316 | CInfo.Kind = BPFPreserveFieldInfoAI; |
317 | CInfo.Metadata = nullptr; |
318 | // Check validity of info_kind as clang did not check this. |
319 | uint64_t InfoKind = getConstant(Call->getArgOperand(1)); |
320 | if (InfoKind >= BPFCoreSharedInfo::MAX_FIELD_RELOC_KIND) |
321 | report_fatal_error("Incorrect info_kind for llvm.bpf.preserve.field.info intrinsic"); |
322 | CInfo.AccessIndex = InfoKind; |
323 | return true; |
324 | } |
325 | if (GV->getName().startswith("llvm.bpf.preserve.type.info")) { |
326 | CInfo.Kind = BPFPreserveFieldInfoAI; |
327 | CInfo.Metadata = Call->getMetadata(LLVMContext::MD_preserve_access_index); |
328 | if (!CInfo.Metadata) |
329 | report_fatal_error("Missing metadata for llvm.preserve.type.info intrinsic"); |
330 | uint64_t Flag = getConstant(Call->getArgOperand(1)); |
331 | if (Flag >= BPFCoreSharedInfo::MAX_PRESERVE_TYPE_INFO_FLAG) |
332 | report_fatal_error("Incorrect flag for llvm.bpf.preserve.type.info intrinsic"); |
333 | if (Flag == BPFCoreSharedInfo::PRESERVE_TYPE_INFO_EXISTENCE) |
334 | CInfo.AccessIndex = BPFCoreSharedInfo::TYPE_EXISTENCE; |
335 | else |
336 | CInfo.AccessIndex = BPFCoreSharedInfo::TYPE_SIZE; |
337 | return true; |
338 | } |
339 | if (GV->getName().startswith("llvm.bpf.preserve.enum.value")) { |
340 | CInfo.Kind = BPFPreserveFieldInfoAI; |
341 | CInfo.Metadata = Call->getMetadata(LLVMContext::MD_preserve_access_index); |
342 | if (!CInfo.Metadata) |
343 | report_fatal_error("Missing metadata for llvm.preserve.enum.value intrinsic"); |
344 | uint64_t Flag = getConstant(Call->getArgOperand(2)); |
345 | if (Flag >= BPFCoreSharedInfo::MAX_PRESERVE_ENUM_VALUE_FLAG) |
346 | report_fatal_error("Incorrect flag for llvm.bpf.preserve.enum.value intrinsic"); |
347 | if (Flag == BPFCoreSharedInfo::PRESERVE_ENUM_VALUE_EXISTENCE) |
348 | CInfo.AccessIndex = BPFCoreSharedInfo::ENUM_VALUE_EXISTENCE; |
349 | else |
350 | CInfo.AccessIndex = BPFCoreSharedInfo::ENUM_VALUE; |
351 | return true; |
352 | } |
353 | |
354 | return false; |
355 | } |
356 | |
357 | void BPFAbstractMemberAccess::replaceWithGEP(std::vector<CallInst *> &CallList, |
358 | uint32_t DimensionIndex, |
359 | uint32_t GEPIndex) { |
360 | for (auto Call : CallList) { |
361 | uint32_t Dimension = 1; |
362 | if (DimensionIndex > 0) |
363 | Dimension = getConstant(Call->getArgOperand(DimensionIndex)); |
364 | |
365 | Constant *Zero = |
366 | ConstantInt::get(Type::getInt32Ty(Call->getParent()->getContext()), 0); |
367 | SmallVector<Value *, 4> IdxList; |
368 | for (unsigned I = 0; I < Dimension; ++I) |
369 | IdxList.push_back(Zero); |
370 | IdxList.push_back(Call->getArgOperand(GEPIndex)); |
371 | |
372 | auto *GEP = GetElementPtrInst::CreateInBounds( |
373 | getBaseElementType(Call), Call->getArgOperand(0), IdxList, "", Call); |
374 | Call->replaceAllUsesWith(GEP); |
375 | Call->eraseFromParent(); |
376 | } |
377 | } |
378 | |
379 | bool BPFAbstractMemberAccess::removePreserveAccessIndexIntrinsic(Function &F) { |
380 | std::vector<CallInst *> PreserveArrayIndexCalls; |
381 | std::vector<CallInst *> PreserveUnionIndexCalls; |
382 | std::vector<CallInst *> PreserveStructIndexCalls; |
383 | bool Found = false; |
384 | |
385 | for (auto &BB : F) |
386 | for (auto &I : BB) { |
387 | auto *Call = dyn_cast<CallInst>(&I); |
388 | CallInfo CInfo; |
389 | if (!IsPreserveDIAccessIndexCall(Call, CInfo)) |
390 | continue; |
391 | |
392 | Found = true; |
393 | if (CInfo.Kind == BPFPreserveArrayAI) |
394 | PreserveArrayIndexCalls.push_back(Call); |
395 | else if (CInfo.Kind == BPFPreserveUnionAI) |
396 | PreserveUnionIndexCalls.push_back(Call); |
397 | else |
398 | PreserveStructIndexCalls.push_back(Call); |
399 | } |
400 | |
401 | // do the following transformation: |
402 | // . addr = preserve_array_access_index(base, dimension, index) |
403 | // is transformed to |
404 | // addr = GEP(base, dimenion's zero's, index) |
405 | // . addr = preserve_union_access_index(base, di_index) |
406 | // is transformed to |
407 | // addr = base, i.e., all usages of "addr" are replaced by "base". |
408 | // . addr = preserve_struct_access_index(base, gep_index, di_index) |
409 | // is transformed to |
410 | // addr = GEP(base, 0, gep_index) |
411 | replaceWithGEP(PreserveArrayIndexCalls, 1, 2); |
412 | replaceWithGEP(PreserveStructIndexCalls, 0, 1); |
413 | for (auto Call : PreserveUnionIndexCalls) { |
414 | Call->replaceAllUsesWith(Call->getArgOperand(0)); |
415 | Call->eraseFromParent(); |
416 | } |
417 | |
418 | return Found; |
419 | } |
420 | |
421 | /// Check whether the access index chain is valid. We check |
422 | /// here because there may be type casts between two |
423 | /// access indexes. We want to ensure memory access still valid. |
424 | bool BPFAbstractMemberAccess::IsValidAIChain(const MDNode *ParentType, |
425 | uint32_t ParentAI, |
426 | const MDNode *ChildType) { |
427 | if (!ChildType) |
428 | return true; // preserve_field_info, no type comparison needed. |
429 | |
430 | const DIType *PType = stripQualifiers(cast<DIType>(ParentType)); |
431 | const DIType *CType = stripQualifiers(cast<DIType>(ChildType)); |
432 | |
433 | // Child is a derived/pointer type, which is due to type casting. |
434 | // Pointer type cannot be in the middle of chain. |
435 | if (isa<DIDerivedType>(CType)) |
436 | return false; |
437 | |
438 | // Parent is a pointer type. |
439 | if (const auto *PtrTy = dyn_cast<DIDerivedType>(PType)) { |
440 | if (PtrTy->getTag() != dwarf::DW_TAG_pointer_type) |
441 | return false; |
442 | return stripQualifiers(PtrTy->getBaseType()) == CType; |
443 | } |
444 | |
445 | // Otherwise, struct/union/array types |
446 | const auto *PTy = dyn_cast<DICompositeType>(PType); |
447 | const auto *CTy = dyn_cast<DICompositeType>(CType); |
448 | assert(PTy && CTy && "ParentType or ChildType is null or not composite")(static_cast <bool> (PTy && CTy && "ParentType or ChildType is null or not composite" ) ? void (0) : __assert_fail ("PTy && CTy && \"ParentType or ChildType is null or not composite\"" , "llvm/lib/Target/BPF/BPFAbstractMemberAccess.cpp", 448, __extension__ __PRETTY_FUNCTION__)); |
449 | |
450 | uint32_t PTyTag = PTy->getTag(); |
451 | assert(PTyTag == dwarf::DW_TAG_array_type ||(static_cast <bool> (PTyTag == dwarf::DW_TAG_array_type || PTyTag == dwarf::DW_TAG_structure_type || PTyTag == dwarf ::DW_TAG_union_type) ? void (0) : __assert_fail ("PTyTag == dwarf::DW_TAG_array_type || PTyTag == dwarf::DW_TAG_structure_type || PTyTag == dwarf::DW_TAG_union_type" , "llvm/lib/Target/BPF/BPFAbstractMemberAccess.cpp", 453, __extension__ __PRETTY_FUNCTION__)) |
452 | PTyTag == dwarf::DW_TAG_structure_type ||(static_cast <bool> (PTyTag == dwarf::DW_TAG_array_type || PTyTag == dwarf::DW_TAG_structure_type || PTyTag == dwarf ::DW_TAG_union_type) ? void (0) : __assert_fail ("PTyTag == dwarf::DW_TAG_array_type || PTyTag == dwarf::DW_TAG_structure_type || PTyTag == dwarf::DW_TAG_union_type" , "llvm/lib/Target/BPF/BPFAbstractMemberAccess.cpp", 453, __extension__ __PRETTY_FUNCTION__)) |
453 | PTyTag == dwarf::DW_TAG_union_type)(static_cast <bool> (PTyTag == dwarf::DW_TAG_array_type || PTyTag == dwarf::DW_TAG_structure_type || PTyTag == dwarf ::DW_TAG_union_type) ? void (0) : __assert_fail ("PTyTag == dwarf::DW_TAG_array_type || PTyTag == dwarf::DW_TAG_structure_type || PTyTag == dwarf::DW_TAG_union_type" , "llvm/lib/Target/BPF/BPFAbstractMemberAccess.cpp", 453, __extension__ __PRETTY_FUNCTION__)); |
454 | |
455 | uint32_t CTyTag = CTy->getTag(); |
456 | assert(CTyTag == dwarf::DW_TAG_array_type ||(static_cast <bool> (CTyTag == dwarf::DW_TAG_array_type || CTyTag == dwarf::DW_TAG_structure_type || CTyTag == dwarf ::DW_TAG_union_type) ? void (0) : __assert_fail ("CTyTag == dwarf::DW_TAG_array_type || CTyTag == dwarf::DW_TAG_structure_type || CTyTag == dwarf::DW_TAG_union_type" , "llvm/lib/Target/BPF/BPFAbstractMemberAccess.cpp", 458, __extension__ __PRETTY_FUNCTION__)) |
457 | CTyTag == dwarf::DW_TAG_structure_type ||(static_cast <bool> (CTyTag == dwarf::DW_TAG_array_type || CTyTag == dwarf::DW_TAG_structure_type || CTyTag == dwarf ::DW_TAG_union_type) ? void (0) : __assert_fail ("CTyTag == dwarf::DW_TAG_array_type || CTyTag == dwarf::DW_TAG_structure_type || CTyTag == dwarf::DW_TAG_union_type" , "llvm/lib/Target/BPF/BPFAbstractMemberAccess.cpp", 458, __extension__ __PRETTY_FUNCTION__)) |
458 | CTyTag == dwarf::DW_TAG_union_type)(static_cast <bool> (CTyTag == dwarf::DW_TAG_array_type || CTyTag == dwarf::DW_TAG_structure_type || CTyTag == dwarf ::DW_TAG_union_type) ? void (0) : __assert_fail ("CTyTag == dwarf::DW_TAG_array_type || CTyTag == dwarf::DW_TAG_structure_type || CTyTag == dwarf::DW_TAG_union_type" , "llvm/lib/Target/BPF/BPFAbstractMemberAccess.cpp", 458, __extension__ __PRETTY_FUNCTION__)); |
459 | |
460 | // Multi dimensional arrays, base element should be the same |
461 | if (PTyTag == dwarf::DW_TAG_array_type && PTyTag == CTyTag) |
462 | return PTy->getBaseType() == CTy->getBaseType(); |
463 | |
464 | DIType *Ty; |
465 | if (PTyTag == dwarf::DW_TAG_array_type) |
466 | Ty = PTy->getBaseType(); |
467 | else |
468 | Ty = dyn_cast<DIType>(PTy->getElements()[ParentAI]); |
469 | |
470 | return dyn_cast<DICompositeType>(stripQualifiers(Ty)) == CTy; |
471 | } |
472 | |
473 | void BPFAbstractMemberAccess::traceAICall(CallInst *Call, |
474 | CallInfo &ParentInfo) { |
475 | for (User *U : Call->users()) { |
476 | Instruction *Inst = dyn_cast<Instruction>(U); |
477 | if (!Inst) |
478 | continue; |
479 | |
480 | if (auto *BI = dyn_cast<BitCastInst>(Inst)) { |
481 | traceBitCast(BI, Call, ParentInfo); |
482 | } else if (auto *CI = dyn_cast<CallInst>(Inst)) { |
483 | CallInfo ChildInfo; |
484 | |
485 | if (IsPreserveDIAccessIndexCall(CI, ChildInfo) && |
486 | IsValidAIChain(ParentInfo.Metadata, ParentInfo.AccessIndex, |
487 | ChildInfo.Metadata)) { |
488 | AIChain[CI] = std::make_pair(Call, ParentInfo); |
489 | traceAICall(CI, ChildInfo); |
490 | } else { |
491 | BaseAICalls[Call] = ParentInfo; |
492 | } |
493 | } else if (auto *GI = dyn_cast<GetElementPtrInst>(Inst)) { |
494 | if (GI->hasAllZeroIndices()) |
495 | traceGEP(GI, Call, ParentInfo); |
496 | else |
497 | BaseAICalls[Call] = ParentInfo; |
498 | } else { |
499 | BaseAICalls[Call] = ParentInfo; |
500 | } |
501 | } |
502 | } |
503 | |
504 | void BPFAbstractMemberAccess::traceBitCast(BitCastInst *BitCast, |
505 | CallInst *Parent, |
506 | CallInfo &ParentInfo) { |
507 | for (User *U : BitCast->users()) { |
508 | Instruction *Inst = dyn_cast<Instruction>(U); |
509 | if (!Inst) |
510 | continue; |
511 | |
512 | if (auto *BI = dyn_cast<BitCastInst>(Inst)) { |
513 | traceBitCast(BI, Parent, ParentInfo); |
514 | } else if (auto *CI = dyn_cast<CallInst>(Inst)) { |
515 | CallInfo ChildInfo; |
516 | if (IsPreserveDIAccessIndexCall(CI, ChildInfo) && |
517 | IsValidAIChain(ParentInfo.Metadata, ParentInfo.AccessIndex, |
518 | ChildInfo.Metadata)) { |
519 | AIChain[CI] = std::make_pair(Parent, ParentInfo); |
520 | traceAICall(CI, ChildInfo); |
521 | } else { |
522 | BaseAICalls[Parent] = ParentInfo; |
523 | } |
524 | } else if (auto *GI = dyn_cast<GetElementPtrInst>(Inst)) { |
525 | if (GI->hasAllZeroIndices()) |
526 | traceGEP(GI, Parent, ParentInfo); |
527 | else |
528 | BaseAICalls[Parent] = ParentInfo; |
529 | } else { |
530 | BaseAICalls[Parent] = ParentInfo; |
531 | } |
532 | } |
533 | } |
534 | |
535 | void BPFAbstractMemberAccess::traceGEP(GetElementPtrInst *GEP, CallInst *Parent, |
536 | CallInfo &ParentInfo) { |
537 | for (User *U : GEP->users()) { |
538 | Instruction *Inst = dyn_cast<Instruction>(U); |
539 | if (!Inst) |
540 | continue; |
541 | |
542 | if (auto *BI = dyn_cast<BitCastInst>(Inst)) { |
543 | traceBitCast(BI, Parent, ParentInfo); |
544 | } else if (auto *CI = dyn_cast<CallInst>(Inst)) { |
545 | CallInfo ChildInfo; |
546 | if (IsPreserveDIAccessIndexCall(CI, ChildInfo) && |
547 | IsValidAIChain(ParentInfo.Metadata, ParentInfo.AccessIndex, |
548 | ChildInfo.Metadata)) { |
549 | AIChain[CI] = std::make_pair(Parent, ParentInfo); |
550 | traceAICall(CI, ChildInfo); |
551 | } else { |
552 | BaseAICalls[Parent] = ParentInfo; |
553 | } |
554 | } else if (auto *GI = dyn_cast<GetElementPtrInst>(Inst)) { |
555 | if (GI->hasAllZeroIndices()) |
556 | traceGEP(GI, Parent, ParentInfo); |
557 | else |
558 | BaseAICalls[Parent] = ParentInfo; |
559 | } else { |
560 | BaseAICalls[Parent] = ParentInfo; |
561 | } |
562 | } |
563 | } |
564 | |
565 | void BPFAbstractMemberAccess::collectAICallChains(Function &F) { |
566 | AIChain.clear(); |
567 | BaseAICalls.clear(); |
568 | |
569 | for (auto &BB : F) |
570 | for (auto &I : BB) { |
571 | CallInfo CInfo; |
572 | auto *Call = dyn_cast<CallInst>(&I); |
573 | if (!IsPreserveDIAccessIndexCall(Call, CInfo) || |
574 | AIChain.find(Call) != AIChain.end()) |
575 | continue; |
576 | |
577 | traceAICall(Call, CInfo); |
578 | } |
579 | } |
580 | |
581 | uint64_t BPFAbstractMemberAccess::getConstant(const Value *IndexValue) { |
582 | const ConstantInt *CV = dyn_cast<ConstantInt>(IndexValue); |
583 | assert(CV)(static_cast <bool> (CV) ? void (0) : __assert_fail ("CV" , "llvm/lib/Target/BPF/BPFAbstractMemberAccess.cpp", 583, __extension__ __PRETTY_FUNCTION__)); |
584 | return CV->getValue().getZExtValue(); |
585 | } |
586 | |
587 | /// Get the start and the end of storage offset for \p MemberTy. |
588 | void BPFAbstractMemberAccess::GetStorageBitRange(DIDerivedType *MemberTy, |
589 | Align RecordAlignment, |
590 | uint32_t &StartBitOffset, |
591 | uint32_t &EndBitOffset) { |
592 | uint32_t MemberBitSize = MemberTy->getSizeInBits(); |
593 | uint32_t MemberBitOffset = MemberTy->getOffsetInBits(); |
594 | |
595 | if (RecordAlignment > 8) { |
596 | // If the Bits are within an aligned 8-byte, set the RecordAlignment |
597 | // to 8, other report the fatal error. |
598 | if (MemberBitOffset / 64 != (MemberBitOffset + MemberBitSize) / 64) |
599 | report_fatal_error("Unsupported field expression for llvm.bpf.preserve.field.info, " |
600 | "requiring too big alignment"); |
601 | RecordAlignment = Align(8); |
602 | } |
603 | |
604 | uint32_t AlignBits = RecordAlignment.value() * 8; |
605 | if (MemberBitSize > AlignBits) |
606 | report_fatal_error("Unsupported field expression for llvm.bpf.preserve.field.info, " |
607 | "bitfield size greater than record alignment"); |
608 | |
609 | StartBitOffset = MemberBitOffset & ~(AlignBits - 1); |
610 | if ((StartBitOffset + AlignBits) < (MemberBitOffset + MemberBitSize)) |
611 | report_fatal_error("Unsupported field expression for llvm.bpf.preserve.field.info, " |
612 | "cross alignment boundary"); |
613 | EndBitOffset = StartBitOffset + AlignBits; |
614 | } |
615 | |
616 | uint32_t BPFAbstractMemberAccess::GetFieldInfo(uint32_t InfoKind, |
617 | DICompositeType *CTy, |
618 | uint32_t AccessIndex, |
619 | uint32_t PatchImm, |
620 | MaybeAlign RecordAlignment) { |
621 | if (InfoKind == BPFCoreSharedInfo::FIELD_EXISTENCE) |
622 | return 1; |
623 | |
624 | uint32_t Tag = CTy->getTag(); |
625 | if (InfoKind == BPFCoreSharedInfo::FIELD_BYTE_OFFSET) { |
626 | if (Tag == dwarf::DW_TAG_array_type) { |
627 | auto *EltTy = stripQualifiers(CTy->getBaseType()); |
628 | PatchImm += AccessIndex * calcArraySize(CTy, 1) * |
629 | (EltTy->getSizeInBits() >> 3); |
630 | } else if (Tag == dwarf::DW_TAG_structure_type) { |
631 | auto *MemberTy = cast<DIDerivedType>(CTy->getElements()[AccessIndex]); |
632 | if (!MemberTy->isBitField()) { |
633 | PatchImm += MemberTy->getOffsetInBits() >> 3; |
634 | } else { |
635 | unsigned SBitOffset, NextSBitOffset; |
636 | GetStorageBitRange(MemberTy, *RecordAlignment, SBitOffset, |
637 | NextSBitOffset); |
638 | PatchImm += SBitOffset >> 3; |
639 | } |
640 | } |
641 | return PatchImm; |
642 | } |
643 | |
644 | if (InfoKind == BPFCoreSharedInfo::FIELD_BYTE_SIZE) { |
645 | if (Tag == dwarf::DW_TAG_array_type) { |
646 | auto *EltTy = stripQualifiers(CTy->getBaseType()); |
647 | return calcArraySize(CTy, 1) * (EltTy->getSizeInBits() >> 3); |
648 | } else { |
649 | auto *MemberTy = cast<DIDerivedType>(CTy->getElements()[AccessIndex]); |
650 | uint32_t SizeInBits = MemberTy->getSizeInBits(); |
651 | if (!MemberTy->isBitField()) |
652 | return SizeInBits >> 3; |
653 | |
654 | unsigned SBitOffset, NextSBitOffset; |
655 | GetStorageBitRange(MemberTy, *RecordAlignment, SBitOffset, |
656 | NextSBitOffset); |
657 | SizeInBits = NextSBitOffset - SBitOffset; |
658 | if (SizeInBits & (SizeInBits - 1)) |
659 | report_fatal_error("Unsupported field expression for llvm.bpf.preserve.field.info"); |
660 | return SizeInBits >> 3; |
661 | } |
662 | } |
663 | |
664 | if (InfoKind == BPFCoreSharedInfo::FIELD_SIGNEDNESS) { |
665 | const DIType *BaseTy; |
666 | if (Tag == dwarf::DW_TAG_array_type) { |
667 | // Signedness only checked when final array elements are accessed. |
668 | if (CTy->getElements().size() != 1) |
669 | report_fatal_error("Invalid array expression for llvm.bpf.preserve.field.info"); |
670 | BaseTy = stripQualifiers(CTy->getBaseType()); |
671 | } else { |
672 | auto *MemberTy = cast<DIDerivedType>(CTy->getElements()[AccessIndex]); |
673 | BaseTy = stripQualifiers(MemberTy->getBaseType()); |
674 | } |
675 | |
676 | // Only basic types and enum types have signedness. |
677 | const auto *BTy = dyn_cast<DIBasicType>(BaseTy); |
678 | while (!BTy) { |
679 | const auto *CompTy = dyn_cast<DICompositeType>(BaseTy); |
680 | // Report an error if the field expression does not have signedness. |
681 | if (!CompTy || CompTy->getTag() != dwarf::DW_TAG_enumeration_type) |
682 | report_fatal_error("Invalid field expression for llvm.bpf.preserve.field.info"); |
683 | BaseTy = stripQualifiers(CompTy->getBaseType()); |
684 | BTy = dyn_cast<DIBasicType>(BaseTy); |
685 | } |
686 | uint32_t Encoding = BTy->getEncoding(); |
687 | return (Encoding == dwarf::DW_ATE_signed || Encoding == dwarf::DW_ATE_signed_char); |
688 | } |
689 | |
690 | if (InfoKind == BPFCoreSharedInfo::FIELD_LSHIFT_U64) { |
691 | // The value is loaded into a value with FIELD_BYTE_SIZE size, |
692 | // and then zero or sign extended to U64. |
693 | // FIELD_LSHIFT_U64 and FIELD_RSHIFT_U64 are operations |
694 | // to extract the original value. |
695 | const Triple &Triple = TM->getTargetTriple(); |
696 | DIDerivedType *MemberTy = nullptr; |
697 | bool IsBitField = false; |
698 | uint32_t SizeInBits; |
699 | |
700 | if (Tag == dwarf::DW_TAG_array_type) { |
701 | auto *EltTy = stripQualifiers(CTy->getBaseType()); |
702 | SizeInBits = calcArraySize(CTy, 1) * EltTy->getSizeInBits(); |
703 | } else { |
704 | MemberTy = cast<DIDerivedType>(CTy->getElements()[AccessIndex]); |
705 | SizeInBits = MemberTy->getSizeInBits(); |
706 | IsBitField = MemberTy->isBitField(); |
707 | } |
708 | |
709 | if (!IsBitField) { |
710 | if (SizeInBits > 64) |
711 | report_fatal_error("too big field size for llvm.bpf.preserve.field.info"); |
712 | return 64 - SizeInBits; |
713 | } |
714 | |
715 | unsigned SBitOffset, NextSBitOffset; |
716 | GetStorageBitRange(MemberTy, *RecordAlignment, SBitOffset, NextSBitOffset); |
717 | if (NextSBitOffset - SBitOffset > 64) |
718 | report_fatal_error("too big field size for llvm.bpf.preserve.field.info"); |
719 | |
720 | unsigned OffsetInBits = MemberTy->getOffsetInBits(); |
721 | if (Triple.getArch() == Triple::bpfel) |
722 | return SBitOffset + 64 - OffsetInBits - SizeInBits; |
723 | else |
724 | return OffsetInBits + 64 - NextSBitOffset; |
725 | } |
726 | |
727 | if (InfoKind == BPFCoreSharedInfo::FIELD_RSHIFT_U64) { |
728 | DIDerivedType *MemberTy = nullptr; |
729 | bool IsBitField = false; |
730 | uint32_t SizeInBits; |
731 | if (Tag == dwarf::DW_TAG_array_type) { |
732 | auto *EltTy = stripQualifiers(CTy->getBaseType()); |
733 | SizeInBits = calcArraySize(CTy, 1) * EltTy->getSizeInBits(); |
734 | } else { |
735 | MemberTy = cast<DIDerivedType>(CTy->getElements()[AccessIndex]); |
736 | SizeInBits = MemberTy->getSizeInBits(); |
737 | IsBitField = MemberTy->isBitField(); |
738 | } |
739 | |
740 | if (!IsBitField) { |
741 | if (SizeInBits > 64) |
742 | report_fatal_error("too big field size for llvm.bpf.preserve.field.info"); |
743 | return 64 - SizeInBits; |
744 | } |
745 | |
746 | unsigned SBitOffset, NextSBitOffset; |
747 | GetStorageBitRange(MemberTy, *RecordAlignment, SBitOffset, NextSBitOffset); |
748 | if (NextSBitOffset - SBitOffset > 64) |
749 | report_fatal_error("too big field size for llvm.bpf.preserve.field.info"); |
750 | |
751 | return 64 - SizeInBits; |
752 | } |
753 | |
754 | llvm_unreachable("Unknown llvm.bpf.preserve.field.info info kind")::llvm::llvm_unreachable_internal("Unknown llvm.bpf.preserve.field.info info kind" , "llvm/lib/Target/BPF/BPFAbstractMemberAccess.cpp", 754); |
755 | } |
756 | |
757 | bool BPFAbstractMemberAccess::HasPreserveFieldInfoCall(CallInfoStack &CallStack) { |
758 | // This is called in error return path, no need to maintain CallStack. |
759 | while (CallStack.size()) { |
760 | auto StackElem = CallStack.top(); |
761 | if (StackElem.second.Kind == BPFPreserveFieldInfoAI) |
762 | return true; |
763 | CallStack.pop(); |
764 | } |
765 | return false; |
766 | } |
767 | |
768 | /// Compute the base of the whole preserve_* intrinsics chains, i.e., the base |
769 | /// pointer of the first preserve_*_access_index call, and construct the access |
770 | /// string, which will be the name of a global variable. |
771 | Value *BPFAbstractMemberAccess::computeBaseAndAccessKey(CallInst *Call, |
772 | CallInfo &CInfo, |
773 | std::string &AccessKey, |
774 | MDNode *&TypeMeta) { |
775 | Value *Base = nullptr; |
776 | std::string TypeName; |
777 | CallInfoStack CallStack; |
778 | |
779 | // Put the access chain into a stack with the top as the head of the chain. |
780 | while (Call) { |
781 | CallStack.push(std::make_pair(Call, CInfo)); |
782 | CInfo = AIChain[Call].second; |
783 | Call = AIChain[Call].first; |
784 | } |
785 | |
786 | // The access offset from the base of the head of chain is also |
787 | // calculated here as all debuginfo types are available. |
788 | |
789 | // Get type name and calculate the first index. |
790 | // We only want to get type name from typedef, structure or union. |
791 | // If user wants a relocation like |
792 | // int *p; ... __builtin_preserve_access_index(&p[4]) ... |
793 | // or |
794 | // int a[10][20]; ... __builtin_preserve_access_index(&a[2][3]) ... |
795 | // we will skip them. |
796 | uint32_t FirstIndex = 0; |
797 | uint32_t PatchImm = 0; // AccessOffset or the requested field info |
798 | uint32_t InfoKind = BPFCoreSharedInfo::FIELD_BYTE_OFFSET; |
799 | while (CallStack.size()) { |
800 | auto StackElem = CallStack.top(); |
801 | Call = StackElem.first; |
Value stored to 'Call' is never read | |
802 | CInfo = StackElem.second; |
803 | |
804 | if (!Base) |
805 | Base = CInfo.Base; |
806 | |
807 | DIType *PossibleTypeDef = stripQualifiers(cast<DIType>(CInfo.Metadata), |
808 | false); |
809 | DIType *Ty = stripQualifiers(PossibleTypeDef); |
810 | if (CInfo.Kind == BPFPreserveUnionAI || |
811 | CInfo.Kind == BPFPreserveStructAI) { |
812 | // struct or union type. If the typedef is in the metadata, always |
813 | // use the typedef. |
814 | TypeName = std::string(PossibleTypeDef->getName()); |
815 | TypeMeta = PossibleTypeDef; |
816 | PatchImm += FirstIndex * (Ty->getSizeInBits() >> 3); |
817 | break; |
818 | } |
819 | |
820 | assert(CInfo.Kind == BPFPreserveArrayAI)(static_cast <bool> (CInfo.Kind == BPFPreserveArrayAI) ? void (0) : __assert_fail ("CInfo.Kind == BPFPreserveArrayAI" , "llvm/lib/Target/BPF/BPFAbstractMemberAccess.cpp", 820, __extension__ __PRETTY_FUNCTION__)); |
821 | |
822 | // Array entries will always be consumed for accumulative initial index. |
823 | CallStack.pop(); |
824 | |
825 | // BPFPreserveArrayAI |
826 | uint64_t AccessIndex = CInfo.AccessIndex; |
827 | |
828 | DIType *BaseTy = nullptr; |
829 | bool CheckElemType = false; |
830 | if (const auto *CTy = dyn_cast<DICompositeType>(Ty)) { |
831 | // array type |
832 | assert(CTy->getTag() == dwarf::DW_TAG_array_type)(static_cast <bool> (CTy->getTag() == dwarf::DW_TAG_array_type ) ? void (0) : __assert_fail ("CTy->getTag() == dwarf::DW_TAG_array_type" , "llvm/lib/Target/BPF/BPFAbstractMemberAccess.cpp", 832, __extension__ __PRETTY_FUNCTION__)); |
833 | |
834 | |
835 | FirstIndex += AccessIndex * calcArraySize(CTy, 1); |
836 | BaseTy = stripQualifiers(CTy->getBaseType()); |
837 | CheckElemType = CTy->getElements().size() == 1; |
838 | } else { |
839 | // pointer type |
840 | auto *DTy = cast<DIDerivedType>(Ty); |
841 | assert(DTy->getTag() == dwarf::DW_TAG_pointer_type)(static_cast <bool> (DTy->getTag() == dwarf::DW_TAG_pointer_type ) ? void (0) : __assert_fail ("DTy->getTag() == dwarf::DW_TAG_pointer_type" , "llvm/lib/Target/BPF/BPFAbstractMemberAccess.cpp", 841, __extension__ __PRETTY_FUNCTION__)); |
842 | |
843 | BaseTy = stripQualifiers(DTy->getBaseType()); |
844 | CTy = dyn_cast<DICompositeType>(BaseTy); |
845 | if (!CTy) { |
846 | CheckElemType = true; |
847 | } else if (CTy->getTag() != dwarf::DW_TAG_array_type) { |
848 | FirstIndex += AccessIndex; |
849 | CheckElemType = true; |
850 | } else { |
851 | FirstIndex += AccessIndex * calcArraySize(CTy, 0); |
852 | } |
853 | } |
854 | |
855 | if (CheckElemType) { |
856 | auto *CTy = dyn_cast<DICompositeType>(BaseTy); |
857 | if (!CTy) { |
858 | if (HasPreserveFieldInfoCall(CallStack)) |
859 | report_fatal_error("Invalid field access for llvm.preserve.field.info intrinsic"); |
860 | return nullptr; |
861 | } |
862 | |
863 | unsigned CTag = CTy->getTag(); |
864 | if (CTag == dwarf::DW_TAG_structure_type || CTag == dwarf::DW_TAG_union_type) { |
865 | TypeName = std::string(CTy->getName()); |
866 | } else { |
867 | if (HasPreserveFieldInfoCall(CallStack)) |
868 | report_fatal_error("Invalid field access for llvm.preserve.field.info intrinsic"); |
869 | return nullptr; |
870 | } |
871 | TypeMeta = CTy; |
872 | PatchImm += FirstIndex * (CTy->getSizeInBits() >> 3); |
873 | break; |
874 | } |
875 | } |
876 | assert(TypeName.size())(static_cast <bool> (TypeName.size()) ? void (0) : __assert_fail ("TypeName.size()", "llvm/lib/Target/BPF/BPFAbstractMemberAccess.cpp" , 876, __extension__ __PRETTY_FUNCTION__)); |
877 | AccessKey += std::to_string(FirstIndex); |
878 | |
879 | // Traverse the rest of access chain to complete offset calculation |
880 | // and access key construction. |
881 | while (CallStack.size()) { |
882 | auto StackElem = CallStack.top(); |
883 | CInfo = StackElem.second; |
884 | CallStack.pop(); |
885 | |
886 | if (CInfo.Kind == BPFPreserveFieldInfoAI) { |
887 | InfoKind = CInfo.AccessIndex; |
888 | if (InfoKind == BPFCoreSharedInfo::FIELD_EXISTENCE) |
889 | PatchImm = 1; |
890 | break; |
891 | } |
892 | |
893 | // If the next Call (the top of the stack) is a BPFPreserveFieldInfoAI, |
894 | // the action will be extracting field info. |
895 | if (CallStack.size()) { |
896 | auto StackElem2 = CallStack.top(); |
897 | CallInfo CInfo2 = StackElem2.second; |
898 | if (CInfo2.Kind == BPFPreserveFieldInfoAI) { |
899 | InfoKind = CInfo2.AccessIndex; |
900 | assert(CallStack.size() == 1)(static_cast <bool> (CallStack.size() == 1) ? void (0) : __assert_fail ("CallStack.size() == 1", "llvm/lib/Target/BPF/BPFAbstractMemberAccess.cpp" , 900, __extension__ __PRETTY_FUNCTION__)); |
901 | } |
902 | } |
903 | |
904 | // Access Index |
905 | uint64_t AccessIndex = CInfo.AccessIndex; |
906 | AccessKey += ":" + std::to_string(AccessIndex); |
907 | |
908 | MDNode *MDN = CInfo.Metadata; |
909 | // At this stage, it cannot be pointer type. |
910 | auto *CTy = cast<DICompositeType>(stripQualifiers(cast<DIType>(MDN))); |
911 | PatchImm = GetFieldInfo(InfoKind, CTy, AccessIndex, PatchImm, |
912 | CInfo.RecordAlignment); |
913 | } |
914 | |
915 | // Access key is the |
916 | // "llvm." + type name + ":" + reloc type + ":" + patched imm + "$" + |
917 | // access string, |
918 | // uniquely identifying one relocation. |
919 | // The prefix "llvm." indicates this is a temporary global, which should |
920 | // not be emitted to ELF file. |
921 | AccessKey = "llvm." + TypeName + ":" + std::to_string(InfoKind) + ":" + |
922 | std::to_string(PatchImm) + "$" + AccessKey; |
923 | |
924 | return Base; |
925 | } |
926 | |
927 | MDNode *BPFAbstractMemberAccess::computeAccessKey(CallInst *Call, |
928 | CallInfo &CInfo, |
929 | std::string &AccessKey, |
930 | bool &IsInt32Ret) { |
931 | DIType *Ty = stripQualifiers(cast<DIType>(CInfo.Metadata), false); |
932 | assert(!Ty->getName().empty())(static_cast <bool> (!Ty->getName().empty()) ? void ( 0) : __assert_fail ("!Ty->getName().empty()", "llvm/lib/Target/BPF/BPFAbstractMemberAccess.cpp" , 932, __extension__ __PRETTY_FUNCTION__)); |
933 | |
934 | int64_t PatchImm; |
935 | std::string AccessStr("0"); |
936 | if (CInfo.AccessIndex == BPFCoreSharedInfo::TYPE_EXISTENCE) { |
937 | PatchImm = 1; |
938 | } else if (CInfo.AccessIndex == BPFCoreSharedInfo::TYPE_SIZE) { |
939 | // typedef debuginfo type has size 0, get the eventual base type. |
940 | DIType *BaseTy = stripQualifiers(Ty, true); |
941 | PatchImm = BaseTy->getSizeInBits() / 8; |
942 | } else { |
943 | // ENUM_VALUE_EXISTENCE and ENUM_VALUE |
944 | IsInt32Ret = false; |
945 | |
946 | // The argument could be a global variable or a getelementptr with base to |
947 | // a global variable depending on whether the clang option `opaque-options` |
948 | // is set or not. |
949 | const GlobalVariable *GV = |
950 | cast<GlobalVariable>(Call->getArgOperand(1)->stripPointerCasts()); |
951 | assert(GV->hasInitializer())(static_cast <bool> (GV->hasInitializer()) ? void (0 ) : __assert_fail ("GV->hasInitializer()", "llvm/lib/Target/BPF/BPFAbstractMemberAccess.cpp" , 951, __extension__ __PRETTY_FUNCTION__)); |
952 | const ConstantDataArray *DA = cast<ConstantDataArray>(GV->getInitializer()); |
953 | assert(DA->isString())(static_cast <bool> (DA->isString()) ? void (0) : __assert_fail ("DA->isString()", "llvm/lib/Target/BPF/BPFAbstractMemberAccess.cpp" , 953, __extension__ __PRETTY_FUNCTION__)); |
954 | StringRef ValueStr = DA->getAsString(); |
955 | |
956 | // ValueStr format: <EnumeratorStr>:<Value> |
957 | size_t Separator = ValueStr.find_first_of(':'); |
958 | StringRef EnumeratorStr = ValueStr.substr(0, Separator); |
959 | |
960 | // Find enumerator index in the debuginfo |
961 | DIType *BaseTy = stripQualifiers(Ty, true); |
962 | const auto *CTy = cast<DICompositeType>(BaseTy); |
963 | assert(CTy->getTag() == dwarf::DW_TAG_enumeration_type)(static_cast <bool> (CTy->getTag() == dwarf::DW_TAG_enumeration_type ) ? void (0) : __assert_fail ("CTy->getTag() == dwarf::DW_TAG_enumeration_type" , "llvm/lib/Target/BPF/BPFAbstractMemberAccess.cpp", 963, __extension__ __PRETTY_FUNCTION__)); |
964 | int EnumIndex = 0; |
965 | for (const auto Element : CTy->getElements()) { |
966 | const auto *Enum = cast<DIEnumerator>(Element); |
967 | if (Enum->getName() == EnumeratorStr) { |
968 | AccessStr = std::to_string(EnumIndex); |
969 | break; |
970 | } |
971 | EnumIndex++; |
972 | } |
973 | |
974 | if (CInfo.AccessIndex == BPFCoreSharedInfo::ENUM_VALUE) { |
975 | StringRef EValueStr = ValueStr.substr(Separator + 1); |
976 | PatchImm = std::stoll(std::string(EValueStr)); |
977 | } else { |
978 | PatchImm = 1; |
979 | } |
980 | } |
981 | |
982 | AccessKey = "llvm." + Ty->getName().str() + ":" + |
983 | std::to_string(CInfo.AccessIndex) + std::string(":") + |
984 | std::to_string(PatchImm) + std::string("$") + AccessStr; |
985 | |
986 | return Ty; |
987 | } |
988 | |
989 | /// Call/Kind is the base preserve_*_access_index() call. Attempts to do |
990 | /// transformation to a chain of relocable GEPs. |
991 | bool BPFAbstractMemberAccess::transformGEPChain(CallInst *Call, |
992 | CallInfo &CInfo) { |
993 | std::string AccessKey; |
994 | MDNode *TypeMeta; |
995 | Value *Base = nullptr; |
996 | bool IsInt32Ret; |
997 | |
998 | IsInt32Ret = CInfo.Kind == BPFPreserveFieldInfoAI; |
999 | if (CInfo.Kind == BPFPreserveFieldInfoAI && CInfo.Metadata) { |
1000 | TypeMeta = computeAccessKey(Call, CInfo, AccessKey, IsInt32Ret); |
1001 | } else { |
1002 | Base = computeBaseAndAccessKey(Call, CInfo, AccessKey, TypeMeta); |
1003 | if (!Base) |
1004 | return false; |
1005 | } |
1006 | |
1007 | BasicBlock *BB = Call->getParent(); |
1008 | GlobalVariable *GV; |
1009 | |
1010 | if (GEPGlobals.find(AccessKey) == GEPGlobals.end()) { |
1011 | IntegerType *VarType; |
1012 | if (IsInt32Ret) |
1013 | VarType = Type::getInt32Ty(BB->getContext()); // 32bit return value |
1014 | else |
1015 | VarType = Type::getInt64Ty(BB->getContext()); // 64bit ptr or enum value |
1016 | |
1017 | GV = new GlobalVariable(*M, VarType, false, GlobalVariable::ExternalLinkage, |
1018 | nullptr, AccessKey); |
1019 | GV->addAttribute(BPFCoreSharedInfo::AmaAttr); |
1020 | GV->setMetadata(LLVMContext::MD_preserve_access_index, TypeMeta); |
1021 | GEPGlobals[AccessKey] = GV; |
1022 | } else { |
1023 | GV = GEPGlobals[AccessKey]; |
1024 | } |
1025 | |
1026 | if (CInfo.Kind == BPFPreserveFieldInfoAI) { |
1027 | // Load the global variable which represents the returned field info. |
1028 | LoadInst *LDInst; |
1029 | if (IsInt32Ret) |
1030 | LDInst = new LoadInst(Type::getInt32Ty(BB->getContext()), GV, "", Call); |
1031 | else |
1032 | LDInst = new LoadInst(Type::getInt64Ty(BB->getContext()), GV, "", Call); |
1033 | |
1034 | Instruction *PassThroughInst = |
1035 | BPFCoreSharedInfo::insertPassThrough(M, BB, LDInst, Call); |
1036 | Call->replaceAllUsesWith(PassThroughInst); |
1037 | Call->eraseFromParent(); |
1038 | return true; |
1039 | } |
1040 | |
1041 | // For any original GEP Call and Base %2 like |
1042 | // %4 = bitcast %struct.net_device** %dev1 to i64* |
1043 | // it is transformed to: |
1044 | // %6 = load llvm.sk_buff:0:50$0:0:0:2:0 |
1045 | // %7 = bitcast %struct.sk_buff* %2 to i8* |
1046 | // %8 = getelementptr i8, i8* %7, %6 |
1047 | // %9 = bitcast i8* %8 to i64* |
1048 | // using %9 instead of %4 |
1049 | // The original Call inst is removed. |
1050 | |
1051 | // Load the global variable. |
1052 | auto *LDInst = new LoadInst(Type::getInt64Ty(BB->getContext()), GV, "", Call); |
1053 | |
1054 | // Generate a BitCast |
1055 | auto *BCInst = new BitCastInst(Base, Type::getInt8PtrTy(BB->getContext())); |
1056 | BB->getInstList().insert(Call->getIterator(), BCInst); |
1057 | |
1058 | // Generate a GetElementPtr |
1059 | auto *GEP = GetElementPtrInst::Create(Type::getInt8Ty(BB->getContext()), |
1060 | BCInst, LDInst); |
1061 | BB->getInstList().insert(Call->getIterator(), GEP); |
1062 | |
1063 | // Generate a BitCast |
1064 | auto *BCInst2 = new BitCastInst(GEP, Call->getType()); |
1065 | BB->getInstList().insert(Call->getIterator(), BCInst2); |
1066 | |
1067 | // For the following code, |
1068 | // Block0: |
1069 | // ... |
1070 | // if (...) goto Block1 else ... |
1071 | // Block1: |
1072 | // %6 = load llvm.sk_buff:0:50$0:0:0:2:0 |
1073 | // %7 = bitcast %struct.sk_buff* %2 to i8* |
1074 | // %8 = getelementptr i8, i8* %7, %6 |
1075 | // ... |
1076 | // goto CommonExit |
1077 | // Block2: |
1078 | // ... |
1079 | // if (...) goto Block3 else ... |
1080 | // Block3: |
1081 | // %6 = load llvm.bpf_map:0:40$0:0:0:2:0 |
1082 | // %7 = bitcast %struct.sk_buff* %2 to i8* |
1083 | // %8 = getelementptr i8, i8* %7, %6 |
1084 | // ... |
1085 | // goto CommonExit |
1086 | // CommonExit |
1087 | // SimplifyCFG may generate: |
1088 | // Block0: |
1089 | // ... |
1090 | // if (...) goto Block_Common else ... |
1091 | // Block2: |
1092 | // ... |
1093 | // if (...) goto Block_Common else ... |
1094 | // Block_Common: |
1095 | // PHI = [llvm.sk_buff:0:50$0:0:0:2:0, llvm.bpf_map:0:40$0:0:0:2:0] |
1096 | // %6 = load PHI |
1097 | // %7 = bitcast %struct.sk_buff* %2 to i8* |
1098 | // %8 = getelementptr i8, i8* %7, %6 |
1099 | // ... |
1100 | // goto CommonExit |
1101 | // For the above code, we cannot perform proper relocation since |
1102 | // "load PHI" has two possible relocations. |
1103 | // |
1104 | // To prevent above tail merging, we use __builtin_bpf_passthrough() |
1105 | // where one of its parameters is a seq_num. Since two |
1106 | // __builtin_bpf_passthrough() funcs will always have different seq_num, |
1107 | // tail merging cannot happen. The __builtin_bpf_passthrough() will be |
1108 | // removed in the beginning of Target IR passes. |
1109 | // |
1110 | // This approach is also used in other places when global var |
1111 | // representing a relocation is used. |
1112 | Instruction *PassThroughInst = |
1113 | BPFCoreSharedInfo::insertPassThrough(M, BB, BCInst2, Call); |
1114 | Call->replaceAllUsesWith(PassThroughInst); |
1115 | Call->eraseFromParent(); |
1116 | |
1117 | return true; |
1118 | } |
1119 | |
1120 | bool BPFAbstractMemberAccess::doTransformation(Function &F) { |
1121 | bool Transformed = false; |
1122 | |
1123 | // Collect PreserveDIAccessIndex Intrinsic call chains. |
1124 | // The call chains will be used to generate the access |
1125 | // patterns similar to GEP. |
1126 | collectAICallChains(F); |
1127 | |
1128 | for (auto &C : BaseAICalls) |
1129 | Transformed = transformGEPChain(C.first, C.second) || Transformed; |
1130 | |
1131 | return removePreserveAccessIndexIntrinsic(F) || Transformed; |
1132 | } |
1133 | |
1134 | PreservedAnalyses |
1135 | BPFAbstractMemberAccessPass::run(Function &F, FunctionAnalysisManager &AM) { |
1136 | return BPFAbstractMemberAccess(TM).run(F) ? PreservedAnalyses::none() |
1137 | : PreservedAnalyses::all(); |
1138 | } |