Bug Summary

File:llvm/lib/Target/BPF/BPFAbstractMemberAccess.cpp
Warning:line 726, column 5
Value stored to 'Call' is never read

Annotated Source Code

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clang -cc1 -triple x86_64-pc-linux-gnu -analyze -disable-free -disable-llvm-verifier -discard-value-names -main-file-name BPFAbstractMemberAccess.cpp -analyzer-store=region -analyzer-opt-analyze-nested-blocks -analyzer-checker=core -analyzer-checker=apiModeling -analyzer-checker=unix -analyzer-checker=deadcode -analyzer-checker=cplusplus -analyzer-checker=security.insecureAPI.UncheckedReturn -analyzer-checker=security.insecureAPI.getpw -analyzer-checker=security.insecureAPI.gets -analyzer-checker=security.insecureAPI.mktemp -analyzer-checker=security.insecureAPI.mkstemp -analyzer-checker=security.insecureAPI.vfork -analyzer-checker=nullability.NullPassedToNonnull -analyzer-checker=nullability.NullReturnedFromNonnull -analyzer-output plist -w -setup-static-analyzer -analyzer-config-compatibility-mode=true -mrelocation-model pic -pic-level 2 -mthread-model posix -mframe-pointer=none -fmath-errno -fno-rounding-math -masm-verbose -mconstructor-aliases -munwind-tables -target-cpu x86-64 -dwarf-column-info -fno-split-dwarf-inlining -debugger-tuning=gdb -ffunction-sections -fdata-sections -resource-dir /usr/lib/llvm-11/lib/clang/11.0.0 -D _DEBUG -D _GNU_SOURCE -D __STDC_CONSTANT_MACROS -D __STDC_FORMAT_MACROS -D __STDC_LIMIT_MACROS -I /build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/build-llvm/lib/Target/BPF -I /build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/llvm/lib/Target/BPF -I /build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/build-llvm/include -I /build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/llvm/include -U NDEBUG -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/c++/6.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/x86_64-linux-gnu/c++/6.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/x86_64-linux-gnu/c++/6.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/c++/6.3.0/backward -internal-isystem /usr/local/include -internal-isystem /usr/lib/llvm-11/lib/clang/11.0.0/include -internal-externc-isystem /usr/include/x86_64-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -O2 -Wno-unused-parameter -Wwrite-strings -Wno-missing-field-initializers -Wno-long-long -Wno-maybe-uninitialized -Wno-comment -std=c++14 -fdeprecated-macro -fdebug-compilation-dir /build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/build-llvm/lib/Target/BPF -fdebug-prefix-map=/build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347=. -ferror-limit 19 -fmessage-length 0 -fvisibility hidden -fvisibility-inlines-hidden -stack-protector 2 -fgnuc-version=4.2.1 -fobjc-runtime=gcc -fdiagnostics-show-option -vectorize-loops -vectorize-slp -analyzer-output=html -analyzer-config stable-report-filename=true -faddrsig -o /tmp/scan-build-2020-03-09-184146-41876-1 -x c++ /build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/llvm/lib/Target/BPF/BPFAbstractMemberAccess.cpp
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/IR/DebugInfoMetadata.h"
81#include "llvm/IR/GlobalVariable.h"
82#include "llvm/IR/Instruction.h"
83#include "llvm/IR/Instructions.h"
84#include "llvm/IR/Module.h"
85#include "llvm/IR/Type.h"
86#include "llvm/IR/User.h"
87#include "llvm/IR/Value.h"
88#include "llvm/Pass.h"
89#include "llvm/Transforms/Utils/BasicBlockUtils.h"
90#include <stack>
91
92#define DEBUG_TYPE"bpf-abstract-member-access" "bpf-abstract-member-access"
93
94namespace llvm {
95const std::string BPFCoreSharedInfo::AmaAttr = "btf_ama";
96} // namespace llvm
97
98using namespace llvm;
99
100namespace {
101
102class BPFAbstractMemberAccess final : public ModulePass {
103 StringRef getPassName() const override {
104 return "BPF Abstract Member Access";
105 }
106
107 bool runOnModule(Module &M) override;
108
109public:
110 static char ID;
111 TargetMachine *TM;
112 // Add optional BPFTargetMachine parameter so that BPF backend can add the phase
113 // with target machine to find out the endianness. The default constructor (without
114 // parameters) is used by the pass manager for managing purposes.
115 BPFAbstractMemberAccess(BPFTargetMachine *TM = nullptr) : ModulePass(ID), TM(TM) {}
116
117 struct CallInfo {
118 uint32_t Kind;
119 uint32_t AccessIndex;
120 uint32_t RecordAlignment;
121 MDNode *Metadata;
122 Value *Base;
123 };
124 typedef std::stack<std::pair<CallInst *, CallInfo>> CallInfoStack;
125
126private:
127 enum : uint32_t {
128 BPFPreserveArrayAI = 1,
129 BPFPreserveUnionAI = 2,
130 BPFPreserveStructAI = 3,
131 BPFPreserveFieldInfoAI = 4,
132 };
133
134 const DataLayout *DL = nullptr;
135
136 std::map<std::string, GlobalVariable *> GEPGlobals;
137 // A map to link preserve_*_access_index instrinsic calls.
138 std::map<CallInst *, std::pair<CallInst *, CallInfo>> AIChain;
139 // A map to hold all the base preserve_*_access_index instrinsic calls.
140 // The base call is not an input of any other preserve_*
141 // intrinsics.
142 std::map<CallInst *, CallInfo> BaseAICalls;
143
144 bool doTransformation(Module &M);
145
146 void traceAICall(CallInst *Call, CallInfo &ParentInfo);
147 void traceBitCast(BitCastInst *BitCast, CallInst *Parent,
148 CallInfo &ParentInfo);
149 void traceGEP(GetElementPtrInst *GEP, CallInst *Parent,
150 CallInfo &ParentInfo);
151 void collectAICallChains(Module &M, Function &F);
152
153 bool IsPreserveDIAccessIndexCall(const CallInst *Call, CallInfo &Cinfo);
154 bool IsValidAIChain(const MDNode *ParentMeta, uint32_t ParentAI,
155 const MDNode *ChildMeta);
156 bool removePreserveAccessIndexIntrinsic(Module &M);
157 void replaceWithGEP(std::vector<CallInst *> &CallList,
158 uint32_t NumOfZerosIndex, uint32_t DIIndex);
159 bool HasPreserveFieldInfoCall(CallInfoStack &CallStack);
160 void GetStorageBitRange(DIDerivedType *MemberTy, uint32_t RecordAlignment,
161 uint32_t &StartBitOffset, uint32_t &EndBitOffset);
162 uint32_t GetFieldInfo(uint32_t InfoKind, DICompositeType *CTy,
163 uint32_t AccessIndex, uint32_t PatchImm,
164 uint32_t RecordAlignment);
165
166 Value *computeBaseAndAccessKey(CallInst *Call, CallInfo &CInfo,
167 std::string &AccessKey, MDNode *&BaseMeta);
168 uint64_t getConstant(const Value *IndexValue);
169 bool transformGEPChain(Module &M, CallInst *Call, CallInfo &CInfo);
170};
171} // End anonymous namespace
172
173char BPFAbstractMemberAccess::ID = 0;
174INITIALIZE_PASS(BPFAbstractMemberAccess, DEBUG_TYPE,static void *initializeBPFAbstractMemberAccessPassOnce(PassRegistry
&Registry) { PassInfo *PI = new PassInfo( "abstracting struct/union member accessees"
, "bpf-abstract-member-access", &BPFAbstractMemberAccess::
ID, PassInfo::NormalCtor_t(callDefaultCtor<BPFAbstractMemberAccess
>), false, false); Registry.registerPass(*PI, true); return
PI; } static llvm::once_flag InitializeBPFAbstractMemberAccessPassFlag
; void llvm::initializeBPFAbstractMemberAccessPass(PassRegistry
&Registry) { llvm::call_once(InitializeBPFAbstractMemberAccessPassFlag
, initializeBPFAbstractMemberAccessPassOnce, std::ref(Registry
)); }
175 "abstracting struct/union member accessees", false, false)static void *initializeBPFAbstractMemberAccessPassOnce(PassRegistry
&Registry) { PassInfo *PI = new PassInfo( "abstracting struct/union member accessees"
, "bpf-abstract-member-access", &BPFAbstractMemberAccess::
ID, PassInfo::NormalCtor_t(callDefaultCtor<BPFAbstractMemberAccess
>), false, false); Registry.registerPass(*PI, true); return
PI; } static llvm::once_flag InitializeBPFAbstractMemberAccessPassFlag
; void llvm::initializeBPFAbstractMemberAccessPass(PassRegistry
&Registry) { llvm::call_once(InitializeBPFAbstractMemberAccessPassFlag
, initializeBPFAbstractMemberAccessPassOnce, std::ref(Registry
)); }
176
177ModulePass *llvm::createBPFAbstractMemberAccess(BPFTargetMachine *TM) {
178 return new BPFAbstractMemberAccess(TM);
179}
180
181bool BPFAbstractMemberAccess::runOnModule(Module &M) {
182 LLVM_DEBUG(dbgs() << "********** Abstract Member Accesses **********\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("bpf-abstract-member-access")) { dbgs() << "********** Abstract Member Accesses **********\n"
; } } while (false)
;
183
184 // Bail out if no debug info.
185 if (M.debug_compile_units().empty())
186 return false;
187
188 DL = &M.getDataLayout();
189 return doTransformation(M);
190}
191
192static bool SkipDIDerivedTag(unsigned Tag, bool skipTypedef) {
193 if (Tag != dwarf::DW_TAG_typedef && Tag != dwarf::DW_TAG_const_type &&
194 Tag != dwarf::DW_TAG_volatile_type &&
195 Tag != dwarf::DW_TAG_restrict_type &&
196 Tag != dwarf::DW_TAG_member)
197 return false;
198 if (Tag == dwarf::DW_TAG_typedef && !skipTypedef)
199 return false;
200 return true;
201}
202
203static DIType * stripQualifiers(DIType *Ty, bool skipTypedef = true) {
204 while (auto *DTy = dyn_cast<DIDerivedType>(Ty)) {
205 if (!SkipDIDerivedTag(DTy->getTag(), skipTypedef))
206 break;
207 Ty = DTy->getBaseType();
208 }
209 return Ty;
210}
211
212static const DIType * stripQualifiers(const DIType *Ty) {
213 while (auto *DTy = dyn_cast<DIDerivedType>(Ty)) {
214 if (!SkipDIDerivedTag(DTy->getTag(), true))
215 break;
216 Ty = DTy->getBaseType();
217 }
218 return Ty;
219}
220
221static uint32_t calcArraySize(const DICompositeType *CTy, uint32_t StartDim) {
222 DINodeArray Elements = CTy->getElements();
223 uint32_t DimSize = 1;
224 for (uint32_t I = StartDim; I < Elements.size(); ++I) {
225 if (auto *Element = dyn_cast_or_null<DINode>(Elements[I]))
226 if (Element->getTag() == dwarf::DW_TAG_subrange_type) {
227 const DISubrange *SR = cast<DISubrange>(Element);
228 auto *CI = SR->getCount().dyn_cast<ConstantInt *>();
229 DimSize *= CI->getSExtValue();
230 }
231 }
232
233 return DimSize;
234}
235
236/// Check whether a call is a preserve_*_access_index intrinsic call or not.
237bool BPFAbstractMemberAccess::IsPreserveDIAccessIndexCall(const CallInst *Call,
238 CallInfo &CInfo) {
239 if (!Call)
240 return false;
241
242 const auto *GV = dyn_cast<GlobalValue>(Call->getCalledValue());
243 if (!GV)
244 return false;
245 if (GV->getName().startswith("llvm.preserve.array.access.index")) {
246 CInfo.Kind = BPFPreserveArrayAI;
247 CInfo.Metadata = Call->getMetadata(LLVMContext::MD_preserve_access_index);
248 if (!CInfo.Metadata)
249 report_fatal_error("Missing metadata for llvm.preserve.array.access.index intrinsic");
250 CInfo.AccessIndex = getConstant(Call->getArgOperand(2));
251 CInfo.Base = Call->getArgOperand(0);
252 CInfo.RecordAlignment =
253 DL->getABITypeAlignment(CInfo.Base->getType()->getPointerElementType());
254 return true;
255 }
256 if (GV->getName().startswith("llvm.preserve.union.access.index")) {
257 CInfo.Kind = BPFPreserveUnionAI;
258 CInfo.Metadata = Call->getMetadata(LLVMContext::MD_preserve_access_index);
259 if (!CInfo.Metadata)
260 report_fatal_error("Missing metadata for llvm.preserve.union.access.index intrinsic");
261 CInfo.AccessIndex = getConstant(Call->getArgOperand(1));
262 CInfo.Base = Call->getArgOperand(0);
263 CInfo.RecordAlignment =
264 DL->getABITypeAlignment(CInfo.Base->getType()->getPointerElementType());
265 return true;
266 }
267 if (GV->getName().startswith("llvm.preserve.struct.access.index")) {
268 CInfo.Kind = BPFPreserveStructAI;
269 CInfo.Metadata = Call->getMetadata(LLVMContext::MD_preserve_access_index);
270 if (!CInfo.Metadata)
271 report_fatal_error("Missing metadata for llvm.preserve.struct.access.index intrinsic");
272 CInfo.AccessIndex = getConstant(Call->getArgOperand(2));
273 CInfo.Base = Call->getArgOperand(0);
274 CInfo.RecordAlignment =
275 DL->getABITypeAlignment(CInfo.Base->getType()->getPointerElementType());
276 return true;
277 }
278 if (GV->getName().startswith("llvm.bpf.preserve.field.info")) {
279 CInfo.Kind = BPFPreserveFieldInfoAI;
280 CInfo.Metadata = nullptr;
281 // Check validity of info_kind as clang did not check this.
282 uint64_t InfoKind = getConstant(Call->getArgOperand(1));
283 if (InfoKind >= BPFCoreSharedInfo::MAX_FIELD_RELOC_KIND)
284 report_fatal_error("Incorrect info_kind for llvm.bpf.preserve.field.info intrinsic");
285 CInfo.AccessIndex = InfoKind;
286 return true;
287 }
288
289 return false;
290}
291
292void BPFAbstractMemberAccess::replaceWithGEP(std::vector<CallInst *> &CallList,
293 uint32_t DimensionIndex,
294 uint32_t GEPIndex) {
295 for (auto Call : CallList) {
296 uint32_t Dimension = 1;
297 if (DimensionIndex > 0)
298 Dimension = getConstant(Call->getArgOperand(DimensionIndex));
299
300 Constant *Zero =
301 ConstantInt::get(Type::getInt32Ty(Call->getParent()->getContext()), 0);
302 SmallVector<Value *, 4> IdxList;
303 for (unsigned I = 0; I < Dimension; ++I)
304 IdxList.push_back(Zero);
305 IdxList.push_back(Call->getArgOperand(GEPIndex));
306
307 auto *GEP = GetElementPtrInst::CreateInBounds(Call->getArgOperand(0),
308 IdxList, "", Call);
309 Call->replaceAllUsesWith(GEP);
310 Call->eraseFromParent();
311 }
312}
313
314bool BPFAbstractMemberAccess::removePreserveAccessIndexIntrinsic(Module &M) {
315 std::vector<CallInst *> PreserveArrayIndexCalls;
316 std::vector<CallInst *> PreserveUnionIndexCalls;
317 std::vector<CallInst *> PreserveStructIndexCalls;
318 bool Found = false;
319
320 for (Function &F : M)
321 for (auto &BB : F)
322 for (auto &I : BB) {
323 auto *Call = dyn_cast<CallInst>(&I);
324 CallInfo CInfo;
325 if (!IsPreserveDIAccessIndexCall(Call, CInfo))
326 continue;
327
328 Found = true;
329 if (CInfo.Kind == BPFPreserveArrayAI)
330 PreserveArrayIndexCalls.push_back(Call);
331 else if (CInfo.Kind == BPFPreserveUnionAI)
332 PreserveUnionIndexCalls.push_back(Call);
333 else
334 PreserveStructIndexCalls.push_back(Call);
335 }
336
337 // do the following transformation:
338 // . addr = preserve_array_access_index(base, dimension, index)
339 // is transformed to
340 // addr = GEP(base, dimenion's zero's, index)
341 // . addr = preserve_union_access_index(base, di_index)
342 // is transformed to
343 // addr = base, i.e., all usages of "addr" are replaced by "base".
344 // . addr = preserve_struct_access_index(base, gep_index, di_index)
345 // is transformed to
346 // addr = GEP(base, 0, gep_index)
347 replaceWithGEP(PreserveArrayIndexCalls, 1, 2);
348 replaceWithGEP(PreserveStructIndexCalls, 0, 1);
349 for (auto Call : PreserveUnionIndexCalls) {
350 Call->replaceAllUsesWith(Call->getArgOperand(0));
351 Call->eraseFromParent();
352 }
353
354 return Found;
355}
356
357/// Check whether the access index chain is valid. We check
358/// here because there may be type casts between two
359/// access indexes. We want to ensure memory access still valid.
360bool BPFAbstractMemberAccess::IsValidAIChain(const MDNode *ParentType,
361 uint32_t ParentAI,
362 const MDNode *ChildType) {
363 if (!ChildType)
364 return true; // preserve_field_info, no type comparison needed.
365
366 const DIType *PType = stripQualifiers(cast<DIType>(ParentType));
367 const DIType *CType = stripQualifiers(cast<DIType>(ChildType));
368
369 // Child is a derived/pointer type, which is due to type casting.
370 // Pointer type cannot be in the middle of chain.
371 if (isa<DIDerivedType>(CType))
372 return false;
373
374 // Parent is a pointer type.
375 if (const auto *PtrTy = dyn_cast<DIDerivedType>(PType)) {
376 if (PtrTy->getTag() != dwarf::DW_TAG_pointer_type)
377 return false;
378 return stripQualifiers(PtrTy->getBaseType()) == CType;
379 }
380
381 // Otherwise, struct/union/array types
382 const auto *PTy = dyn_cast<DICompositeType>(PType);
383 const auto *CTy = dyn_cast<DICompositeType>(CType);
384 assert(PTy && CTy && "ParentType or ChildType is null or not composite")((PTy && CTy && "ParentType or ChildType is null or not composite"
) ? static_cast<void> (0) : __assert_fail ("PTy && CTy && \"ParentType or ChildType is null or not composite\""
, "/build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/llvm/lib/Target/BPF/BPFAbstractMemberAccess.cpp"
, 384, __PRETTY_FUNCTION__))
;
385
386 uint32_t PTyTag = PTy->getTag();
387 assert(PTyTag == dwarf::DW_TAG_array_type ||((PTyTag == dwarf::DW_TAG_array_type || PTyTag == dwarf::DW_TAG_structure_type
|| PTyTag == dwarf::DW_TAG_union_type) ? static_cast<void
> (0) : __assert_fail ("PTyTag == dwarf::DW_TAG_array_type || PTyTag == dwarf::DW_TAG_structure_type || PTyTag == dwarf::DW_TAG_union_type"
, "/build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/llvm/lib/Target/BPF/BPFAbstractMemberAccess.cpp"
, 389, __PRETTY_FUNCTION__))
388 PTyTag == dwarf::DW_TAG_structure_type ||((PTyTag == dwarf::DW_TAG_array_type || PTyTag == dwarf::DW_TAG_structure_type
|| PTyTag == dwarf::DW_TAG_union_type) ? static_cast<void
> (0) : __assert_fail ("PTyTag == dwarf::DW_TAG_array_type || PTyTag == dwarf::DW_TAG_structure_type || PTyTag == dwarf::DW_TAG_union_type"
, "/build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/llvm/lib/Target/BPF/BPFAbstractMemberAccess.cpp"
, 389, __PRETTY_FUNCTION__))
389 PTyTag == dwarf::DW_TAG_union_type)((PTyTag == dwarf::DW_TAG_array_type || PTyTag == dwarf::DW_TAG_structure_type
|| PTyTag == dwarf::DW_TAG_union_type) ? static_cast<void
> (0) : __assert_fail ("PTyTag == dwarf::DW_TAG_array_type || PTyTag == dwarf::DW_TAG_structure_type || PTyTag == dwarf::DW_TAG_union_type"
, "/build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/llvm/lib/Target/BPF/BPFAbstractMemberAccess.cpp"
, 389, __PRETTY_FUNCTION__))
;
390
391 uint32_t CTyTag = CTy->getTag();
392 assert(CTyTag == dwarf::DW_TAG_array_type ||((CTyTag == dwarf::DW_TAG_array_type || CTyTag == dwarf::DW_TAG_structure_type
|| CTyTag == dwarf::DW_TAG_union_type) ? static_cast<void
> (0) : __assert_fail ("CTyTag == dwarf::DW_TAG_array_type || CTyTag == dwarf::DW_TAG_structure_type || CTyTag == dwarf::DW_TAG_union_type"
, "/build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/llvm/lib/Target/BPF/BPFAbstractMemberAccess.cpp"
, 394, __PRETTY_FUNCTION__))
393 CTyTag == dwarf::DW_TAG_structure_type ||((CTyTag == dwarf::DW_TAG_array_type || CTyTag == dwarf::DW_TAG_structure_type
|| CTyTag == dwarf::DW_TAG_union_type) ? static_cast<void
> (0) : __assert_fail ("CTyTag == dwarf::DW_TAG_array_type || CTyTag == dwarf::DW_TAG_structure_type || CTyTag == dwarf::DW_TAG_union_type"
, "/build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/llvm/lib/Target/BPF/BPFAbstractMemberAccess.cpp"
, 394, __PRETTY_FUNCTION__))
394 CTyTag == dwarf::DW_TAG_union_type)((CTyTag == dwarf::DW_TAG_array_type || CTyTag == dwarf::DW_TAG_structure_type
|| CTyTag == dwarf::DW_TAG_union_type) ? static_cast<void
> (0) : __assert_fail ("CTyTag == dwarf::DW_TAG_array_type || CTyTag == dwarf::DW_TAG_structure_type || CTyTag == dwarf::DW_TAG_union_type"
, "/build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/llvm/lib/Target/BPF/BPFAbstractMemberAccess.cpp"
, 394, __PRETTY_FUNCTION__))
;
395
396 // Multi dimensional arrays, base element should be the same
397 if (PTyTag == dwarf::DW_TAG_array_type && PTyTag == CTyTag)
398 return PTy->getBaseType() == CTy->getBaseType();
399
400 DIType *Ty;
401 if (PTyTag == dwarf::DW_TAG_array_type)
402 Ty = PTy->getBaseType();
403 else
404 Ty = dyn_cast<DIType>(PTy->getElements()[ParentAI]);
405
406 return dyn_cast<DICompositeType>(stripQualifiers(Ty)) == CTy;
407}
408
409void BPFAbstractMemberAccess::traceAICall(CallInst *Call,
410 CallInfo &ParentInfo) {
411 for (User *U : Call->users()) {
412 Instruction *Inst = dyn_cast<Instruction>(U);
413 if (!Inst)
414 continue;
415
416 if (auto *BI = dyn_cast<BitCastInst>(Inst)) {
417 traceBitCast(BI, Call, ParentInfo);
418 } else if (auto *CI = dyn_cast<CallInst>(Inst)) {
419 CallInfo ChildInfo;
420
421 if (IsPreserveDIAccessIndexCall(CI, ChildInfo) &&
422 IsValidAIChain(ParentInfo.Metadata, ParentInfo.AccessIndex,
423 ChildInfo.Metadata)) {
424 AIChain[CI] = std::make_pair(Call, ParentInfo);
425 traceAICall(CI, ChildInfo);
426 } else {
427 BaseAICalls[Call] = ParentInfo;
428 }
429 } else if (auto *GI = dyn_cast<GetElementPtrInst>(Inst)) {
430 if (GI->hasAllZeroIndices())
431 traceGEP(GI, Call, ParentInfo);
432 else
433 BaseAICalls[Call] = ParentInfo;
434 } else {
435 BaseAICalls[Call] = ParentInfo;
436 }
437 }
438}
439
440void BPFAbstractMemberAccess::traceBitCast(BitCastInst *BitCast,
441 CallInst *Parent,
442 CallInfo &ParentInfo) {
443 for (User *U : BitCast->users()) {
444 Instruction *Inst = dyn_cast<Instruction>(U);
445 if (!Inst)
446 continue;
447
448 if (auto *BI = dyn_cast<BitCastInst>(Inst)) {
449 traceBitCast(BI, Parent, ParentInfo);
450 } else if (auto *CI = dyn_cast<CallInst>(Inst)) {
451 CallInfo ChildInfo;
452 if (IsPreserveDIAccessIndexCall(CI, ChildInfo) &&
453 IsValidAIChain(ParentInfo.Metadata, ParentInfo.AccessIndex,
454 ChildInfo.Metadata)) {
455 AIChain[CI] = std::make_pair(Parent, ParentInfo);
456 traceAICall(CI, ChildInfo);
457 } else {
458 BaseAICalls[Parent] = ParentInfo;
459 }
460 } else if (auto *GI = dyn_cast<GetElementPtrInst>(Inst)) {
461 if (GI->hasAllZeroIndices())
462 traceGEP(GI, Parent, ParentInfo);
463 else
464 BaseAICalls[Parent] = ParentInfo;
465 } else {
466 BaseAICalls[Parent] = ParentInfo;
467 }
468 }
469}
470
471void BPFAbstractMemberAccess::traceGEP(GetElementPtrInst *GEP, CallInst *Parent,
472 CallInfo &ParentInfo) {
473 for (User *U : GEP->users()) {
474 Instruction *Inst = dyn_cast<Instruction>(U);
475 if (!Inst)
476 continue;
477
478 if (auto *BI = dyn_cast<BitCastInst>(Inst)) {
479 traceBitCast(BI, Parent, ParentInfo);
480 } else if (auto *CI = dyn_cast<CallInst>(Inst)) {
481 CallInfo ChildInfo;
482 if (IsPreserveDIAccessIndexCall(CI, ChildInfo) &&
483 IsValidAIChain(ParentInfo.Metadata, ParentInfo.AccessIndex,
484 ChildInfo.Metadata)) {
485 AIChain[CI] = std::make_pair(Parent, ParentInfo);
486 traceAICall(CI, ChildInfo);
487 } else {
488 BaseAICalls[Parent] = ParentInfo;
489 }
490 } else if (auto *GI = dyn_cast<GetElementPtrInst>(Inst)) {
491 if (GI->hasAllZeroIndices())
492 traceGEP(GI, Parent, ParentInfo);
493 else
494 BaseAICalls[Parent] = ParentInfo;
495 } else {
496 BaseAICalls[Parent] = ParentInfo;
497 }
498 }
499}
500
501void BPFAbstractMemberAccess::collectAICallChains(Module &M, Function &F) {
502 AIChain.clear();
503 BaseAICalls.clear();
504
505 for (auto &BB : F)
506 for (auto &I : BB) {
507 CallInfo CInfo;
508 auto *Call = dyn_cast<CallInst>(&I);
509 if (!IsPreserveDIAccessIndexCall(Call, CInfo) ||
510 AIChain.find(Call) != AIChain.end())
511 continue;
512
513 traceAICall(Call, CInfo);
514 }
515}
516
517uint64_t BPFAbstractMemberAccess::getConstant(const Value *IndexValue) {
518 const ConstantInt *CV = dyn_cast<ConstantInt>(IndexValue);
519 assert(CV)((CV) ? static_cast<void> (0) : __assert_fail ("CV", "/build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/llvm/lib/Target/BPF/BPFAbstractMemberAccess.cpp"
, 519, __PRETTY_FUNCTION__))
;
520 return CV->getValue().getZExtValue();
521}
522
523/// Get the start and the end of storage offset for \p MemberTy.
524void BPFAbstractMemberAccess::GetStorageBitRange(DIDerivedType *MemberTy,
525 uint32_t RecordAlignment,
526 uint32_t &StartBitOffset,
527 uint32_t &EndBitOffset) {
528 uint32_t MemberBitSize = MemberTy->getSizeInBits();
529 uint32_t MemberBitOffset = MemberTy->getOffsetInBits();
530 uint32_t AlignBits = RecordAlignment * 8;
531 if (RecordAlignment > 8 || MemberBitSize > AlignBits)
532 report_fatal_error("Unsupported field expression for llvm.bpf.preserve.field.info, "
533 "requiring too big alignment");
534
535 StartBitOffset = MemberBitOffset & ~(AlignBits - 1);
536 if ((StartBitOffset + AlignBits) < (MemberBitOffset + MemberBitSize))
537 report_fatal_error("Unsupported field expression for llvm.bpf.preserve.field.info, "
538 "cross alignment boundary");
539 EndBitOffset = StartBitOffset + AlignBits;
540}
541
542uint32_t BPFAbstractMemberAccess::GetFieldInfo(uint32_t InfoKind,
543 DICompositeType *CTy,
544 uint32_t AccessIndex,
545 uint32_t PatchImm,
546 uint32_t RecordAlignment) {
547 if (InfoKind == BPFCoreSharedInfo::FIELD_EXISTENCE)
548 return 1;
549
550 uint32_t Tag = CTy->getTag();
551 if (InfoKind == BPFCoreSharedInfo::FIELD_BYTE_OFFSET) {
552 if (Tag == dwarf::DW_TAG_array_type) {
553 auto *EltTy = stripQualifiers(CTy->getBaseType());
554 PatchImm += AccessIndex * calcArraySize(CTy, 1) *
555 (EltTy->getSizeInBits() >> 3);
556 } else if (Tag == dwarf::DW_TAG_structure_type) {
557 auto *MemberTy = cast<DIDerivedType>(CTy->getElements()[AccessIndex]);
558 if (!MemberTy->isBitField()) {
559 PatchImm += MemberTy->getOffsetInBits() >> 3;
560 } else {
561 unsigned SBitOffset, NextSBitOffset;
562 GetStorageBitRange(MemberTy, RecordAlignment, SBitOffset,
563 NextSBitOffset);
564 PatchImm += SBitOffset >> 3;
565 }
566 }
567 return PatchImm;
568 }
569
570 if (InfoKind == BPFCoreSharedInfo::FIELD_BYTE_SIZE) {
571 if (Tag == dwarf::DW_TAG_array_type) {
572 auto *EltTy = stripQualifiers(CTy->getBaseType());
573 return calcArraySize(CTy, 1) * (EltTy->getSizeInBits() >> 3);
574 } else {
575 auto *MemberTy = cast<DIDerivedType>(CTy->getElements()[AccessIndex]);
576 uint32_t SizeInBits = MemberTy->getSizeInBits();
577 if (!MemberTy->isBitField())
578 return SizeInBits >> 3;
579
580 unsigned SBitOffset, NextSBitOffset;
581 GetStorageBitRange(MemberTy, RecordAlignment, SBitOffset, NextSBitOffset);
582 SizeInBits = NextSBitOffset - SBitOffset;
583 if (SizeInBits & (SizeInBits - 1))
584 report_fatal_error("Unsupported field expression for llvm.bpf.preserve.field.info");
585 return SizeInBits >> 3;
586 }
587 }
588
589 if (InfoKind == BPFCoreSharedInfo::FIELD_SIGNEDNESS) {
590 const DIType *BaseTy;
591 if (Tag == dwarf::DW_TAG_array_type) {
592 // Signedness only checked when final array elements are accessed.
593 if (CTy->getElements().size() != 1)
594 report_fatal_error("Invalid array expression for llvm.bpf.preserve.field.info");
595 BaseTy = stripQualifiers(CTy->getBaseType());
596 } else {
597 auto *MemberTy = cast<DIDerivedType>(CTy->getElements()[AccessIndex]);
598 BaseTy = stripQualifiers(MemberTy->getBaseType());
599 }
600
601 // Only basic types and enum types have signedness.
602 const auto *BTy = dyn_cast<DIBasicType>(BaseTy);
603 while (!BTy) {
604 const auto *CompTy = dyn_cast<DICompositeType>(BaseTy);
605 // Report an error if the field expression does not have signedness.
606 if (!CompTy || CompTy->getTag() != dwarf::DW_TAG_enumeration_type)
607 report_fatal_error("Invalid field expression for llvm.bpf.preserve.field.info");
608 BaseTy = stripQualifiers(CompTy->getBaseType());
609 BTy = dyn_cast<DIBasicType>(BaseTy);
610 }
611 uint32_t Encoding = BTy->getEncoding();
612 return (Encoding == dwarf::DW_ATE_signed || Encoding == dwarf::DW_ATE_signed_char);
613 }
614
615 if (InfoKind == BPFCoreSharedInfo::FIELD_LSHIFT_U64) {
616 // The value is loaded into a value with FIELD_BYTE_SIZE size,
617 // and then zero or sign extended to U64.
618 // FIELD_LSHIFT_U64 and FIELD_RSHIFT_U64 are operations
619 // to extract the original value.
620 const Triple &Triple = TM->getTargetTriple();
621 DIDerivedType *MemberTy = nullptr;
622 bool IsBitField = false;
623 uint32_t SizeInBits;
624
625 if (Tag == dwarf::DW_TAG_array_type) {
626 auto *EltTy = stripQualifiers(CTy->getBaseType());
627 SizeInBits = calcArraySize(CTy, 1) * EltTy->getSizeInBits();
628 } else {
629 MemberTy = cast<DIDerivedType>(CTy->getElements()[AccessIndex]);
630 SizeInBits = MemberTy->getSizeInBits();
631 IsBitField = MemberTy->isBitField();
632 }
633
634 if (!IsBitField) {
635 if (SizeInBits > 64)
636 report_fatal_error("too big field size for llvm.bpf.preserve.field.info");
637 return 64 - SizeInBits;
638 }
639
640 unsigned SBitOffset, NextSBitOffset;
641 GetStorageBitRange(MemberTy, RecordAlignment, SBitOffset, NextSBitOffset);
642 if (NextSBitOffset - SBitOffset > 64)
643 report_fatal_error("too big field size for llvm.bpf.preserve.field.info");
644
645 unsigned OffsetInBits = MemberTy->getOffsetInBits();
646 if (Triple.getArch() == Triple::bpfel)
647 return SBitOffset + 64 - OffsetInBits - SizeInBits;
648 else
649 return OffsetInBits + 64 - NextSBitOffset;
650 }
651
652 if (InfoKind == BPFCoreSharedInfo::FIELD_RSHIFT_U64) {
653 DIDerivedType *MemberTy = nullptr;
654 bool IsBitField = false;
655 uint32_t SizeInBits;
656 if (Tag == dwarf::DW_TAG_array_type) {
657 auto *EltTy = stripQualifiers(CTy->getBaseType());
658 SizeInBits = calcArraySize(CTy, 1) * EltTy->getSizeInBits();
659 } else {
660 MemberTy = cast<DIDerivedType>(CTy->getElements()[AccessIndex]);
661 SizeInBits = MemberTy->getSizeInBits();
662 IsBitField = MemberTy->isBitField();
663 }
664
665 if (!IsBitField) {
666 if (SizeInBits > 64)
667 report_fatal_error("too big field size for llvm.bpf.preserve.field.info");
668 return 64 - SizeInBits;
669 }
670
671 unsigned SBitOffset, NextSBitOffset;
672 GetStorageBitRange(MemberTy, RecordAlignment, SBitOffset, NextSBitOffset);
673 if (NextSBitOffset - SBitOffset > 64)
674 report_fatal_error("too big field size for llvm.bpf.preserve.field.info");
675
676 return 64 - SizeInBits;
677 }
678
679 llvm_unreachable("Unknown llvm.bpf.preserve.field.info info kind")::llvm::llvm_unreachable_internal("Unknown llvm.bpf.preserve.field.info info kind"
, "/build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/llvm/lib/Target/BPF/BPFAbstractMemberAccess.cpp"
, 679)
;
680}
681
682bool BPFAbstractMemberAccess::HasPreserveFieldInfoCall(CallInfoStack &CallStack) {
683 // This is called in error return path, no need to maintain CallStack.
684 while (CallStack.size()) {
685 auto StackElem = CallStack.top();
686 if (StackElem.second.Kind == BPFPreserveFieldInfoAI)
687 return true;
688 CallStack.pop();
689 }
690 return false;
691}
692
693/// Compute the base of the whole preserve_* intrinsics chains, i.e., the base
694/// pointer of the first preserve_*_access_index call, and construct the access
695/// string, which will be the name of a global variable.
696Value *BPFAbstractMemberAccess::computeBaseAndAccessKey(CallInst *Call,
697 CallInfo &CInfo,
698 std::string &AccessKey,
699 MDNode *&TypeMeta) {
700 Value *Base = nullptr;
701 std::string TypeName;
702 CallInfoStack CallStack;
703
704 // Put the access chain into a stack with the top as the head of the chain.
705 while (Call) {
706 CallStack.push(std::make_pair(Call, CInfo));
707 CInfo = AIChain[Call].second;
708 Call = AIChain[Call].first;
709 }
710
711 // The access offset from the base of the head of chain is also
712 // calculated here as all debuginfo types are available.
713
714 // Get type name and calculate the first index.
715 // We only want to get type name from typedef, structure or union.
716 // If user wants a relocation like
717 // int *p; ... __builtin_preserve_access_index(&p[4]) ...
718 // or
719 // int a[10][20]; ... __builtin_preserve_access_index(&a[2][3]) ...
720 // we will skip them.
721 uint32_t FirstIndex = 0;
722 uint32_t PatchImm = 0; // AccessOffset or the requested field info
723 uint32_t InfoKind = BPFCoreSharedInfo::FIELD_BYTE_OFFSET;
724 while (CallStack.size()) {
725 auto StackElem = CallStack.top();
726 Call = StackElem.first;
Value stored to 'Call' is never read
727 CInfo = StackElem.second;
728
729 if (!Base)
730 Base = CInfo.Base;
731
732 DIType *PossibleTypeDef = stripQualifiers(cast<DIType>(CInfo.Metadata),
733 false);
734 DIType *Ty = stripQualifiers(PossibleTypeDef);
735 if (CInfo.Kind == BPFPreserveUnionAI ||
736 CInfo.Kind == BPFPreserveStructAI) {
737 // struct or union type. If the typedef is in the metadata, always
738 // use the typedef.
739 TypeName = std::string(PossibleTypeDef->getName());
740 TypeMeta = PossibleTypeDef;
741 PatchImm += FirstIndex * (Ty->getSizeInBits() >> 3);
742 break;
743 }
744
745 assert(CInfo.Kind == BPFPreserveArrayAI)((CInfo.Kind == BPFPreserveArrayAI) ? static_cast<void>
(0) : __assert_fail ("CInfo.Kind == BPFPreserveArrayAI", "/build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/llvm/lib/Target/BPF/BPFAbstractMemberAccess.cpp"
, 745, __PRETTY_FUNCTION__))
;
746
747 // Array entries will always be consumed for accumulative initial index.
748 CallStack.pop();
749
750 // BPFPreserveArrayAI
751 uint64_t AccessIndex = CInfo.AccessIndex;
752
753 DIType *BaseTy = nullptr;
754 bool CheckElemType = false;
755 if (const auto *CTy = dyn_cast<DICompositeType>(Ty)) {
756 // array type
757 assert(CTy->getTag() == dwarf::DW_TAG_array_type)((CTy->getTag() == dwarf::DW_TAG_array_type) ? static_cast
<void> (0) : __assert_fail ("CTy->getTag() == dwarf::DW_TAG_array_type"
, "/build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/llvm/lib/Target/BPF/BPFAbstractMemberAccess.cpp"
, 757, __PRETTY_FUNCTION__))
;
758
759
760 FirstIndex += AccessIndex * calcArraySize(CTy, 1);
761 BaseTy = stripQualifiers(CTy->getBaseType());
762 CheckElemType = CTy->getElements().size() == 1;
763 } else {
764 // pointer type
765 auto *DTy = cast<DIDerivedType>(Ty);
766 assert(DTy->getTag() == dwarf::DW_TAG_pointer_type)((DTy->getTag() == dwarf::DW_TAG_pointer_type) ? static_cast
<void> (0) : __assert_fail ("DTy->getTag() == dwarf::DW_TAG_pointer_type"
, "/build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/llvm/lib/Target/BPF/BPFAbstractMemberAccess.cpp"
, 766, __PRETTY_FUNCTION__))
;
767
768 BaseTy = stripQualifiers(DTy->getBaseType());
769 CTy = dyn_cast<DICompositeType>(BaseTy);
770 if (!CTy) {
771 CheckElemType = true;
772 } else if (CTy->getTag() != dwarf::DW_TAG_array_type) {
773 FirstIndex += AccessIndex;
774 CheckElemType = true;
775 } else {
776 FirstIndex += AccessIndex * calcArraySize(CTy, 0);
777 }
778 }
779
780 if (CheckElemType) {
781 auto *CTy = dyn_cast<DICompositeType>(BaseTy);
782 if (!CTy) {
783 if (HasPreserveFieldInfoCall(CallStack))
784 report_fatal_error("Invalid field access for llvm.preserve.field.info intrinsic");
785 return nullptr;
786 }
787
788 unsigned CTag = CTy->getTag();
789 if (CTag == dwarf::DW_TAG_structure_type || CTag == dwarf::DW_TAG_union_type) {
790 TypeName = std::string(CTy->getName());
791 } else {
792 if (HasPreserveFieldInfoCall(CallStack))
793 report_fatal_error("Invalid field access for llvm.preserve.field.info intrinsic");
794 return nullptr;
795 }
796 TypeMeta = CTy;
797 PatchImm += FirstIndex * (CTy->getSizeInBits() >> 3);
798 break;
799 }
800 }
801 assert(TypeName.size())((TypeName.size()) ? static_cast<void> (0) : __assert_fail
("TypeName.size()", "/build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/llvm/lib/Target/BPF/BPFAbstractMemberAccess.cpp"
, 801, __PRETTY_FUNCTION__))
;
802 AccessKey += std::to_string(FirstIndex);
803
804 // Traverse the rest of access chain to complete offset calculation
805 // and access key construction.
806 while (CallStack.size()) {
807 auto StackElem = CallStack.top();
808 CInfo = StackElem.second;
809 CallStack.pop();
810
811 if (CInfo.Kind == BPFPreserveFieldInfoAI)
812 break;
813
814 // If the next Call (the top of the stack) is a BPFPreserveFieldInfoAI,
815 // the action will be extracting field info.
816 if (CallStack.size()) {
817 auto StackElem2 = CallStack.top();
818 CallInfo CInfo2 = StackElem2.second;
819 if (CInfo2.Kind == BPFPreserveFieldInfoAI) {
820 InfoKind = CInfo2.AccessIndex;
821 assert(CallStack.size() == 1)((CallStack.size() == 1) ? static_cast<void> (0) : __assert_fail
("CallStack.size() == 1", "/build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/llvm/lib/Target/BPF/BPFAbstractMemberAccess.cpp"
, 821, __PRETTY_FUNCTION__))
;
822 }
823 }
824
825 // Access Index
826 uint64_t AccessIndex = CInfo.AccessIndex;
827 AccessKey += ":" + std::to_string(AccessIndex);
828
829 MDNode *MDN = CInfo.Metadata;
830 uint32_t RecordAlignment = CInfo.RecordAlignment;
831 // At this stage, it cannot be pointer type.
832 auto *CTy = cast<DICompositeType>(stripQualifiers(cast<DIType>(MDN)));
833 PatchImm = GetFieldInfo(InfoKind, CTy, AccessIndex, PatchImm,
834 RecordAlignment);
835 }
836
837 // Access key is the
838 // "llvm." + type name + ":" + reloc type + ":" + patched imm + "$" +
839 // access string,
840 // uniquely identifying one relocation.
841 // The prefix "llvm." indicates this is a temporary global, which should
842 // not be emitted to ELF file.
843 AccessKey = "llvm." + TypeName + ":" + std::to_string(InfoKind) + ":" +
844 std::to_string(PatchImm) + "$" + AccessKey;
845
846 return Base;
847}
848
849/// Call/Kind is the base preserve_*_access_index() call. Attempts to do
850/// transformation to a chain of relocable GEPs.
851bool BPFAbstractMemberAccess::transformGEPChain(Module &M, CallInst *Call,
852 CallInfo &CInfo) {
853 std::string AccessKey;
854 MDNode *TypeMeta;
855 Value *Base =
856 computeBaseAndAccessKey(Call, CInfo, AccessKey, TypeMeta);
857 if (!Base)
858 return false;
859
860 BasicBlock *BB = Call->getParent();
861 GlobalVariable *GV;
862
863 if (GEPGlobals.find(AccessKey) == GEPGlobals.end()) {
864 IntegerType *VarType;
865 if (CInfo.Kind == BPFPreserveFieldInfoAI)
866 VarType = Type::getInt32Ty(BB->getContext()); // 32bit return value
867 else
868 VarType = Type::getInt64Ty(BB->getContext()); // 64bit ptr arith
869
870 GV = new GlobalVariable(M, VarType, false, GlobalVariable::ExternalLinkage,
871 NULL__null, AccessKey);
872 GV->addAttribute(BPFCoreSharedInfo::AmaAttr);
873 GV->setMetadata(LLVMContext::MD_preserve_access_index, TypeMeta);
874 GEPGlobals[AccessKey] = GV;
875 } else {
876 GV = GEPGlobals[AccessKey];
877 }
878
879 if (CInfo.Kind == BPFPreserveFieldInfoAI) {
880 // Load the global variable which represents the returned field info.
881 auto *LDInst = new LoadInst(Type::getInt32Ty(BB->getContext()), GV);
882 BB->getInstList().insert(Call->getIterator(), LDInst);
883 Call->replaceAllUsesWith(LDInst);
884 Call->eraseFromParent();
885 return true;
886 }
887
888 // For any original GEP Call and Base %2 like
889 // %4 = bitcast %struct.net_device** %dev1 to i64*
890 // it is transformed to:
891 // %6 = load sk_buff:50:$0:0:0:2:0
892 // %7 = bitcast %struct.sk_buff* %2 to i8*
893 // %8 = getelementptr i8, i8* %7, %6
894 // %9 = bitcast i8* %8 to i64*
895 // using %9 instead of %4
896 // The original Call inst is removed.
897
898 // Load the global variable.
899 auto *LDInst = new LoadInst(Type::getInt64Ty(BB->getContext()), GV);
900 BB->getInstList().insert(Call->getIterator(), LDInst);
901
902 // Generate a BitCast
903 auto *BCInst = new BitCastInst(Base, Type::getInt8PtrTy(BB->getContext()));
904 BB->getInstList().insert(Call->getIterator(), BCInst);
905
906 // Generate a GetElementPtr
907 auto *GEP = GetElementPtrInst::Create(Type::getInt8Ty(BB->getContext()),
908 BCInst, LDInst);
909 BB->getInstList().insert(Call->getIterator(), GEP);
910
911 // Generate a BitCast
912 auto *BCInst2 = new BitCastInst(GEP, Call->getType());
913 BB->getInstList().insert(Call->getIterator(), BCInst2);
914
915 Call->replaceAllUsesWith(BCInst2);
916 Call->eraseFromParent();
917
918 return true;
919}
920
921bool BPFAbstractMemberAccess::doTransformation(Module &M) {
922 bool Transformed = false;
923
924 for (Function &F : M) {
925 // Collect PreserveDIAccessIndex Intrinsic call chains.
926 // The call chains will be used to generate the access
927 // patterns similar to GEP.
928 collectAICallChains(M, F);
929
930 for (auto &C : BaseAICalls)
931 Transformed = transformGEPChain(M, C.first, C.second) || Transformed;
932 }
933
934 return removePreserveAccessIndexIntrinsic(M) || Transformed;
935}