1//===- JITSymbol.h - JIT symbol abstraction ---------------------*- C++ -*-===//
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// Abstraction for target process addresses.
10//
11//===----------------------------------------------------------------------===//
12
13#ifndef LLVM_EXECUTIONENGINE_JITSYMBOL_H
14#define LLVM_EXECUTIONENGINE_JITSYMBOL_H
15
16#include <algorithm>
17#include <cassert>
18#include <cstddef>
19#include <cstdint>
20#include <functional>
21#include <map>
22#include <set>
23#include <string>
24
25#include "llvm/ADT/BitmaskEnum.h"
26#include "llvm/ADT/FunctionExtras.h"
27#include "llvm/ADT/StringRef.h"
28#include "llvm/Support/Error.h"
29
30namespace llvm {
31
32class GlobalValue;
33class GlobalValueSummary;
34
35namespace object {
36
37class SymbolRef;
38
39} // end namespace object
40
41/// Represents an address in the target process's address space.
42using JITTargetAddress = uint64_t;
43
44/// Convert a JITTargetAddress to a pointer.
45///
46/// Note: This is a raw cast of the address bit pattern to the given pointer
47/// type. When casting to a function pointer in order to execute JIT'd code
48/// jitTargetAddressToFunction should be preferred, as it will also perform
49/// pointer signing on targets that require it.
50template <typename T> T jitTargetAddressToPointer(JITTargetAddress Addr) {
51 static_assert(std::is_pointer<T>::value, "T must be a pointer type");
52 uintptr_t IntPtr = static_cast<uintptr_t>(Addr);
53 assert(IntPtr == Addr && "JITTargetAddress value out of range for uintptr_t");
54 return reinterpret_cast<T>(IntPtr);
55}
56
57/// Convert a JITTargetAddress to a callable function pointer.
58///
59/// Casts the given address to a callable function pointer. This operation
60/// will perform pointer signing for platforms that require it (e.g. arm64e).
61template <typename T> T jitTargetAddressToFunction(JITTargetAddress Addr) {
62 static_assert(std::is_pointer<T>::value &&
63 std::is_function<std::remove_pointer_t<T>>::value,
64 "T must be a function pointer type");
65 return jitTargetAddressToPointer<T>(Addr);
66}
67
68/// Convert a pointer to a JITTargetAddress.
69template <typename T> JITTargetAddress pointerToJITTargetAddress(T *Ptr) {
70 return static_cast<JITTargetAddress>(reinterpret_cast<uintptr_t>(Ptr));
71}
72
73/// Flags for symbols in the JIT.
74class JITSymbolFlags {
75public:
76 using UnderlyingType = uint8_t;
77 using TargetFlagsType = uint8_t;
78
79 enum FlagNames : UnderlyingType {
80 None = 0,
81 HasError = 1U << 0,
82 Weak = 1U << 1,
83 Common = 1U << 2,
84 Absolute = 1U << 3,
85 Exported = 1U << 4,
86 Callable = 1U << 5,
87 MaterializationSideEffectsOnly = 1U << 6,
88 LLVM_MARK_AS_BITMASK_ENUM( // LargestValue =
89 MaterializationSideEffectsOnly)
90 };
91
92 /// Default-construct a JITSymbolFlags instance.
93 JITSymbolFlags() = default;
94
95 /// Construct a JITSymbolFlags instance from the given flags.
96 JITSymbolFlags(FlagNames Flags) : Flags(Flags) {}
97
98 /// Construct a JITSymbolFlags instance from the given flags and target
99 /// flags.
100 JITSymbolFlags(FlagNames Flags, TargetFlagsType TargetFlags)
101 : TargetFlags(TargetFlags), Flags(Flags) {}
102
103 /// Implicitly convert to bool. Returns true if any flag is set.
104 explicit operator bool() const { return Flags != None || TargetFlags != 0; }
105
106 /// Compare for equality.
107 bool operator==(const JITSymbolFlags &RHS) const {
108 return Flags == RHS.Flags && TargetFlags == RHS.TargetFlags;
109 }
110
111 /// Bitwise AND-assignment for FlagNames.
112 JITSymbolFlags &operator&=(const FlagNames &RHS) {
113 Flags &= RHS;
114 return *this;
115 }
116
117 /// Bitwise OR-assignment for FlagNames.
118 JITSymbolFlags &operator|=(const FlagNames &RHS) {
119 Flags |= RHS;
120 return *this;
121 }
122
123 /// Return true if there was an error retrieving this symbol.
124 bool hasError() const {
125 return (Flags & HasError) == HasError;
126 }
127
128 /// Returns true if the Weak flag is set.
129 bool isWeak() const {
130 return (Flags & Weak) == Weak;
131 }
132
133 /// Returns true if the Common flag is set.
134 bool isCommon() const {
135 return (Flags & Common) == Common;
136 }
137
138 /// Returns true if the symbol isn't weak or common.
139 bool isStrong() const {
140 return !isWeak() && !isCommon();
141 }
142
143 /// Returns true if the Exported flag is set.
144 bool isExported() const {
145 return (Flags & Exported) == Exported;
146 }
147
148 /// Returns true if the given symbol is known to be callable.
149 bool isCallable() const { return (Flags & Callable) == Callable; }
150
151 /// Returns true if this symbol is a materialization-side-effects-only
152 /// symbol. Such symbols do not have a real address. They exist to trigger
153 /// and support synchronization of materialization side effects, e.g. for
154 /// collecting initialization information. These symbols will vanish from
155 /// the symbol table immediately upon reaching the ready state, and will
156 /// appear to queries as if they were never defined (except that query
157 /// callback execution will be delayed until they reach the ready state).
158 /// MaterializationSideEffectOnly symbols should only be queried using the
159 /// SymbolLookupFlags::WeaklyReferencedSymbol flag (see
160 /// llvm/include/llvm/ExecutionEngine/Orc/Core.h).
161 bool hasMaterializationSideEffectsOnly() const {
162 return (Flags & MaterializationSideEffectsOnly) ==
163 MaterializationSideEffectsOnly;
164 }
165
166 /// Get the underlying flags value as an integer.
167 UnderlyingType getRawFlagsValue() const {
168 return static_cast<UnderlyingType>(Flags);
169 }
170
171 /// Return a reference to the target-specific flags.
172 TargetFlagsType& getTargetFlags() { return TargetFlags; }
173
174 /// Return a reference to the target-specific flags.
175 const TargetFlagsType& getTargetFlags() const { return TargetFlags; }
176
177 /// Construct a JITSymbolFlags value based on the flags of the given global
178 /// value.
179 static JITSymbolFlags fromGlobalValue(const GlobalValue &GV);
180
181 /// Construct a JITSymbolFlags value based on the flags of the given global
182 /// value summary.
183 static JITSymbolFlags fromSummary(GlobalValueSummary *S);
184
185 /// Construct a JITSymbolFlags value based on the flags of the given libobject
186 /// symbol.
187 static Expected<JITSymbolFlags>
188 fromObjectSymbol(const object::SymbolRef &Symbol);
189
190private:
191 TargetFlagsType TargetFlags = 0;
192 FlagNames Flags = None;
193};
194
195inline JITSymbolFlags operator&(const JITSymbolFlags &LHS,
196 const JITSymbolFlags::FlagNames &RHS) {
197 JITSymbolFlags Tmp = LHS;
198 Tmp &= RHS;
199 return Tmp;
200}
201
202inline JITSymbolFlags operator|(const JITSymbolFlags &LHS,
203 const JITSymbolFlags::FlagNames &RHS) {
204 JITSymbolFlags Tmp = LHS;
205 Tmp |= RHS;
206 return Tmp;
207}
208
209/// ARM-specific JIT symbol flags.
210/// FIXME: This should be moved into a target-specific header.
211class ARMJITSymbolFlags {
212public:
213 ARMJITSymbolFlags() = default;
214
215 enum FlagNames {
216 None = 0,
217 Thumb = 1 << 0
218 };
219
220 operator JITSymbolFlags::TargetFlagsType&() { return Flags; }
221
222 static ARMJITSymbolFlags fromObjectSymbol(const object::SymbolRef &Symbol);
223
224private:
225 JITSymbolFlags::TargetFlagsType Flags = 0;
226};
227
228/// Represents a symbol that has been evaluated to an address already.
229class JITEvaluatedSymbol {
230public:
231 JITEvaluatedSymbol() = default;
232
233 /// Create a 'null' symbol.
234 JITEvaluatedSymbol(std::nullptr_t) {}
235
236 /// Create a symbol for the given address and flags.
237 JITEvaluatedSymbol(JITTargetAddress Address, JITSymbolFlags Flags)
238 : Address(Address), Flags(Flags) {}
239
240 /// Create a symbol from the given pointer with the given flags.
241 template <typename T>
242 static JITEvaluatedSymbol
243 fromPointer(T *P, JITSymbolFlags Flags = JITSymbolFlags::Exported) {
244 return JITEvaluatedSymbol(pointerToJITTargetAddress(P), Flags);
245 }
246
247 /// An evaluated symbol converts to 'true' if its address is non-zero.
248 explicit operator bool() const { return Address != 0; }
249
250 /// Return the address of this symbol.
251 JITTargetAddress getAddress() const { return Address; }
252
253 /// Return the flags for this symbol.
254 JITSymbolFlags getFlags() const { return Flags; }
255
256 /// Set the flags for this symbol.
257 void setFlags(JITSymbolFlags Flags) { this->Flags = std::move(Flags); }
258
259private:
260 JITTargetAddress Address = 0;
261 JITSymbolFlags Flags;
262};
263
264/// Represents a symbol in the JIT.
265class JITSymbol {
266public:
267 using GetAddressFtor = unique_function<Expected<JITTargetAddress>()>;
268
269 /// Create a 'null' symbol, used to represent a "symbol not found"
270 /// result from a successful (non-erroneous) lookup.
271 JITSymbol(std::nullptr_t)
272 : CachedAddr(0) {}
273
274 /// Create a JITSymbol representing an error in the symbol lookup
275 /// process (e.g. a network failure during a remote lookup).
276 JITSymbol(Error Err)
277 : Err(std::move(Err)), Flags(JITSymbolFlags::HasError) {}
278
279 /// Create a symbol for a definition with a known address.
280 JITSymbol(JITTargetAddress Addr, JITSymbolFlags Flags)
281 : CachedAddr(Addr), Flags(Flags) {}
282
283 /// Construct a JITSymbol from a JITEvaluatedSymbol.
284 JITSymbol(JITEvaluatedSymbol Sym)
285 : CachedAddr(Sym.getAddress()), Flags(Sym.getFlags()) {}
286
287 /// Create a symbol for a definition that doesn't have a known address
288 /// yet.
289 /// @param GetAddress A functor to materialize a definition (fixing the
290 /// address) on demand.
291 ///
292 /// This constructor allows a JIT layer to provide a reference to a symbol
293 /// definition without actually materializing the definition up front. The
294 /// user can materialize the definition at any time by calling the getAddress
295 /// method.
296 JITSymbol(GetAddressFtor GetAddress, JITSymbolFlags Flags)
297 : GetAddress(std::move(GetAddress)), CachedAddr(0), Flags(Flags) {}
298
299 JITSymbol(const JITSymbol&) = delete;
300 JITSymbol& operator=(const JITSymbol&) = delete;
301
302 JITSymbol(JITSymbol &&Other)
303 : GetAddress(std::move(Other.GetAddress)), Flags(std::move(Other.Flags)) {
304 if (Flags.hasError())
305 Err = std::move(Other.Err);
306 else
307 CachedAddr = std::move(Other.CachedAddr);
308 }
309
310 JITSymbol& operator=(JITSymbol &&Other) {
311 GetAddress = std::move(Other.GetAddress);
312 Flags = std::move(Other.Flags);
313 if (Flags.hasError())
314 Err = std::move(Other.Err);
315 else
316 CachedAddr = std::move(Other.CachedAddr);
317 return *this;
318 }
319
320 ~JITSymbol() {
321 if (Flags.hasError())
322 Err.~Error();
323 else
324 CachedAddr.~JITTargetAddress();
325 }
326
327 /// Returns true if the symbol exists, false otherwise.
328 explicit operator bool() const {
329 return !Flags.hasError() && (CachedAddr || GetAddress);
330 }
331
332 /// Move the error field value out of this JITSymbol.
333 Error takeError() {
334 if (Flags.hasError())
335 return std::move(Err);
336 return Error::success();
337 }
338
339 /// Get the address of the symbol in the target address space. Returns
340 /// '0' if the symbol does not exist.
341 Expected<JITTargetAddress> getAddress() {
342 assert(!Flags.hasError() && "getAddress called on error value");
343 if (GetAddress) {
344 if (auto CachedAddrOrErr = GetAddress()) {
345 GetAddress = nullptr;
346 CachedAddr = *CachedAddrOrErr;
347 assert(CachedAddr && "Symbol could not be materialized.");
348 } else
349 return CachedAddrOrErr.takeError();
350 }
351 return CachedAddr;
352 }
353
354 JITSymbolFlags getFlags() const { return Flags; }
355
356private:
357 GetAddressFtor GetAddress;
358 union {
359 JITTargetAddress CachedAddr;
360 Error Err;
361 };
362 JITSymbolFlags Flags;
363};
364
365/// Symbol resolution interface.
366///
367/// Allows symbol flags and addresses to be looked up by name.
368/// Symbol queries are done in bulk (i.e. you request resolution of a set of
369/// symbols, rather than a single one) to reduce IPC overhead in the case of
370/// remote JITing, and expose opportunities for parallel compilation.
371class JITSymbolResolver {
372public:
373 using LookupSet = std::set<StringRef>;
374 using LookupResult = std::map<StringRef, JITEvaluatedSymbol>;
375 using OnResolvedFunction = unique_function<void(Expected<LookupResult>)>;
376
377 virtual ~JITSymbolResolver() = default;
378
379 /// Returns the fully resolved address and flags for each of the given
380 /// symbols.
381 ///
382 /// This method will return an error if any of the given symbols can not be
383 /// resolved, or if the resolution process itself triggers an error.
384 virtual void lookup(const LookupSet &Symbols,
385 OnResolvedFunction OnResolved) = 0;
386
387 /// Returns the subset of the given symbols that should be materialized by
388 /// the caller. Only weak/common symbols should be looked up, as strong
389 /// definitions are implicitly always part of the caller's responsibility.
390 virtual Expected<LookupSet>
391 getResponsibilitySet(const LookupSet &Symbols) = 0;
392
393 /// Specify if this resolver can return valid symbols with zero value.
394 virtual bool allowsZeroSymbols() { return false; }
395
396private:
397 virtual void anchor();
398};
399
400/// Legacy symbol resolution interface.
401class LegacyJITSymbolResolver : public JITSymbolResolver {
402public:
403 /// Performs lookup by, for each symbol, first calling
404 /// findSymbolInLogicalDylib and if that fails calling
405 /// findSymbol.
406 void lookup(const LookupSet &Symbols, OnResolvedFunction OnResolved) final;
407
408 /// Performs flags lookup by calling findSymbolInLogicalDylib and
409 /// returning the flags value for that symbol.
410 Expected<LookupSet> getResponsibilitySet(const LookupSet &Symbols) final;
411
412 /// This method returns the address of the specified symbol if it exists
413 /// within the logical dynamic library represented by this JITSymbolResolver.
414 /// Unlike findSymbol, queries through this interface should return addresses
415 /// for hidden symbols.
416 ///
417 /// This is of particular importance for the Orc JIT APIs, which support lazy
418 /// compilation by breaking up modules: Each of those broken out modules
419 /// must be able to resolve hidden symbols provided by the others. Clients
420 /// writing memory managers for MCJIT can usually ignore this method.
421 ///
422 /// This method will be queried by RuntimeDyld when checking for previous
423 /// definitions of common symbols.
424 virtual JITSymbol findSymbolInLogicalDylib(const std::string &Name) = 0;
425
426 /// This method returns the address of the specified function or variable.
427 /// It is used to resolve symbols during module linking.
428 ///
429 /// If the returned symbol's address is equal to ~0ULL then RuntimeDyld will
430 /// skip all relocations for that symbol, and the client will be responsible
431 /// for handling them manually.
432 virtual JITSymbol findSymbol(const std::string &Name) = 0;
433
434private:
435 void anchor() override;
436};
437
438} // end namespace llvm
439
440#endif // LLVM_EXECUTIONENGINE_JITSYMBOL_H
441