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1 //===-- llvm/Support/WinARMEH.h - Windows on ARM EH Constants ---*- C++ -*-===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 
10 #ifndef LLVM_SUPPORT_ARMWINEH_H
11 #define LLVM_SUPPORT_ARMWINEH_H
12 
13 #include "llvm/ADT/ArrayRef.h"
14 #include "llvm/Support/Endian.h"
15 
16 namespace llvm {
17 namespace ARM {
18 namespace WinEH {
19 enum class RuntimeFunctionFlag {
20   RFF_Unpacked,       /// unpacked entry
21   RFF_Packed,         /// packed entry
22   RFF_PackedFragment, /// packed entry representing a fragment
23   RFF_Reserved,       /// reserved
24 };
25 
26 enum class ReturnType {
27   RT_POP,             /// return via pop {pc} (L flag must be set)
28   RT_B,               /// 16-bit branch
29   RT_BW,              /// 32-bit branch
30   RT_NoEpilogue,      /// no epilogue (fragment)
31 };
32 
33 /// RuntimeFunction - An entry in the table of procedure data (.pdata)
34 ///
35 ///  3 3 2 2 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0
36 ///  1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0
37 /// +---------------------------------------------------------------+
38 /// |                     Function Start RVA                        |
39 /// +-------------------+-+-+-+-----+-+---+---------------------+---+
40 /// |    Stack Adjust   |C|L|R| Reg |H|Ret|   Function Length   |Flg|
41 /// +-------------------+-+-+-+-----+-+---+---------------------+---+
42 ///
43 /// Flag : 2-bit field with the following meanings:
44 ///   - 00 = packed unwind data not used; reamining bits point to .xdata record
45 ///   - 01 = packed unwind data
46 ///   - 10 = packed unwind data, function assumed to have no prologue; useful
47 ///          for function fragments that are discontiguous with the start of the
48 ///          function
49 ///   - 11 = reserved
50 /// Function Length : 11-bit field providing the length of the entire function
51 ///                   in bytes, divided by 2; if the function is greater than
52 ///                   4KB, a full .xdata record must be used instead
53 /// Ret : 2-bit field indicating how the function returns
54 ///   - 00 = return via pop {pc} (the L bit must be set)
55 ///   - 01 = return via 16-bit branch
56 ///   - 10 = return via 32-bit branch
57 ///   - 11 = no epilogue; useful for function fragments that may only contain a
58 ///          prologue but the epilogue is elsewhere
59 /// H : 1-bit flag indicating whether the function "homes" the integer parameter
60 ///     registers (r0-r3), allocating 16-bytes on the stack
61 /// Reg : 3-bit field indicating the index of the last saved non-volatile
62 ///       register.  If the R bit is set to 0, then only integer registers are
63 ///       saved (r4-rN, where N is 4 + Reg).  If the R bit is set to 1, then
64 ///       only floating-point registers are being saved (d8-dN, where N is
65 ///       8 + Reg).  The special case of the R bit being set to 1 and Reg equal
66 ///       to 7 indicates that no registers are saved.
67 /// R : 1-bit flag indicating whether the non-volatile registers are integer or
68 ///     floating-point.  0 indicates integer, 1 indicates floating-point.  The
69 ///     special case of the R-flag being set and Reg being set to 7 indicates
70 ///     that no non-volatile registers are saved.
71 /// L : 1-bit flag indicating whether the function saves/restores the link
72 ///     register (LR)
73 /// C : 1-bit flag indicating whether the function includes extra instructions
74 ///     to setup a frame chain for fast walking.  If this flag is set, r11 is
75 ///     implicitly added to the list of saved non-volatile integer registers.
76 /// Stack Adjust : 10-bit field indicating the number of bytes of stack that are
77 ///                allocated for this function.  Only values between 0x000 and
78 ///                0x3f3 can be directly encoded.  If the value is 0x3f4 or
79 ///                greater, then the low 4 bits have special meaning as follows:
80 ///                - Bit 0-1
81 ///                  indicate the number of words' of adjustment (1-4), minus 1
82 ///                - Bit 2
83 ///                  indicates if the prologue combined adjustment into push
84 ///                - Bit 3
85 ///                  indicates if the epilogue combined adjustment into pop
86 ///
87 /// RESTRICTIONS:
88 ///   - IF C is SET:
89 ///     + L flag must be set since frame chaining requires r11 and lr
90 ///     + r11 must NOT be included in the set of registers described by Reg
91 ///   - IF Ret is 0:
92 ///     + L flag must be set
93 
94 // NOTE: RuntimeFunction is meant to be a simple class that provides raw access
95 // to all fields in the structure.  The accessor methods reflect the names of
96 // the bitfields that they correspond to.  Although some obvious simplifications
97 // are possible via merging of methods, it would prevent the use of this class
98 // to fully inspect the contents of the data structure which is particularly
99 // useful for scenarios such as llvm-readobj to aid in testing.
100 
101 class RuntimeFunction {
102 public:
103   const support::ulittle32_t BeginAddress;
104   const support::ulittle32_t UnwindData;
105 
RuntimeFunction(const support::ulittle32_t * Data)106   RuntimeFunction(const support::ulittle32_t *Data)
107     : BeginAddress(Data[0]), UnwindData(Data[1]) {}
108 
RuntimeFunction(const support::ulittle32_t BeginAddress,const support::ulittle32_t UnwindData)109   RuntimeFunction(const support::ulittle32_t BeginAddress,
110                   const support::ulittle32_t UnwindData)
111     : BeginAddress(BeginAddress), UnwindData(UnwindData) {}
112 
Flag()113   RuntimeFunctionFlag Flag() const {
114     return RuntimeFunctionFlag(UnwindData & 0x3);
115   }
116 
ExceptionInformationRVA()117   uint32_t ExceptionInformationRVA() const {
118     assert(Flag() == RuntimeFunctionFlag::RFF_Unpacked &&
119            "unpacked form required for this operation");
120     return (UnwindData & ~0x3);
121   }
122 
PackedUnwindData()123   uint32_t PackedUnwindData() const {
124     assert((Flag() == RuntimeFunctionFlag::RFF_Packed ||
125             Flag() == RuntimeFunctionFlag::RFF_PackedFragment) &&
126            "packed form required for this operation");
127     return (UnwindData & ~0x3);
128   }
FunctionLength()129   uint32_t FunctionLength() const {
130     assert((Flag() == RuntimeFunctionFlag::RFF_Packed ||
131             Flag() == RuntimeFunctionFlag::RFF_PackedFragment) &&
132            "packed form required for this operation");
133     return (((UnwindData & 0x00001ffc) >> 2) << 1);
134   }
Ret()135   ReturnType Ret() const {
136     assert((Flag() == RuntimeFunctionFlag::RFF_Packed ||
137             Flag() == RuntimeFunctionFlag::RFF_PackedFragment) &&
138            "packed form required for this operation");
139     assert(((UnwindData & 0x00006000) || L()) && "L must be set to 1");
140     return ReturnType((UnwindData & 0x00006000) >> 13);
141   }
H()142   bool H() const {
143     assert((Flag() == RuntimeFunctionFlag::RFF_Packed ||
144             Flag() == RuntimeFunctionFlag::RFF_PackedFragment) &&
145            "packed form required for this operation");
146     return ((UnwindData & 0x00008000) >> 15);
147   }
Reg()148   uint8_t Reg() const {
149     assert((Flag() == RuntimeFunctionFlag::RFF_Packed ||
150             Flag() == RuntimeFunctionFlag::RFF_PackedFragment) &&
151            "packed form required for this operation");
152     return ((UnwindData & 0x00070000) >> 16);
153   }
R()154   bool R() const {
155     assert((Flag() == RuntimeFunctionFlag::RFF_Packed ||
156             Flag() == RuntimeFunctionFlag::RFF_PackedFragment) &&
157            "packed form required for this operation");
158     return ((UnwindData & 0x00080000) >> 19);
159   }
L()160   bool L() const {
161     assert((Flag() == RuntimeFunctionFlag::RFF_Packed ||
162             Flag() == RuntimeFunctionFlag::RFF_PackedFragment) &&
163            "packed form required for this operation");
164     return ((UnwindData & 0x00100000) >> 20);
165   }
C()166   bool C() const {
167     assert((Flag() == RuntimeFunctionFlag::RFF_Packed ||
168             Flag() == RuntimeFunctionFlag::RFF_PackedFragment) &&
169            "packed form required for this operation");
170     assert(((~UnwindData & 0x00200000) || L()) &&
171            "L flag must be set, chaining requires r11 and LR");
172     assert(((~UnwindData & 0x00200000) || (Reg() < 7) || R()) &&
173            "r11 must not be included in Reg; C implies r11");
174     return ((UnwindData & 0x00200000) >> 21);
175   }
StackAdjust()176   uint16_t StackAdjust() const {
177     assert((Flag() == RuntimeFunctionFlag::RFF_Packed ||
178             Flag() == RuntimeFunctionFlag::RFF_PackedFragment) &&
179            "packed form required for this operation");
180     return ((UnwindData & 0xffc00000) >> 22);
181   }
182 };
183 
184 /// PrologueFolding - pseudo-flag derived from Stack Adjust indicating that the
185 /// prologue has stack adjustment combined into the push
PrologueFolding(const RuntimeFunction & RF)186 inline bool PrologueFolding(const RuntimeFunction &RF) {
187   return RF.StackAdjust() >= 0x3f4 && (RF.StackAdjust() & 0x4);
188 }
189 /// Epilogue - pseudo-flag derived from Stack Adjust indicating that the
190 /// epilogue has stack adjustment combined into the pop
EpilogueFolding(const RuntimeFunction & RF)191 inline bool EpilogueFolding(const RuntimeFunction &RF) {
192   return RF.StackAdjust() >= 0x3f4 && (RF.StackAdjust() & 0x8);
193 }
194 /// StackAdjustment - calculated stack adjustment in words.  The stack
195 /// adjustment should be determined via this function to account for the special
196 /// handling the special encoding when the value is >= 0x3f4.
StackAdjustment(const RuntimeFunction & RF)197 inline uint16_t StackAdjustment(const RuntimeFunction &RF) {
198   uint16_t Adjustment = RF.StackAdjust();
199   if (Adjustment >= 0x3f4)
200     return (Adjustment & 0x3) ? ((Adjustment & 0x3) << 2) - 1 : 0;
201   return Adjustment;
202 }
203 
204 /// SavedRegisterMask - Utility function to calculate the set of saved general
205 /// purpose (r0-r15) and VFP (d0-d31) registers.
206 std::pair<uint16_t, uint32_t> SavedRegisterMask(const RuntimeFunction &RF);
207 
208 /// ExceptionDataRecord - An entry in the table of exception data (.xdata)
209 ///
210 ///  3 3 2 2 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0
211 ///  1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0
212 /// +-------+---------+-+-+-+---+-----------------------------------+
213 /// | C Wrd | Epi Cnt |F|E|X|Ver|         Function Length           |
214 /// +-------+--------+'-'-'-'---'---+-------------------------------+
215 /// |    Reserved    |Ex. Code Words|   (Extended Epilogue Count)   |
216 /// +-------+--------+--------------+-------------------------------+
217 ///
218 /// Function Length : 18-bit field indicating the total length of the function
219 ///                   in bytes divided by 2.  If a function is larger than
220 ///                   512KB, then multiple pdata and xdata records must be used.
221 /// Vers : 2-bit field describing the version of the remaining structure.  Only
222 ///        version 0 is currently defined (values 1-3 are not permitted).
223 /// X : 1-bit field indicating the presence of exception data
224 /// E : 1-bit field indicating that the single epilogue is packed into the
225 ///     header
226 /// F : 1-bit field indicating that the record describes a function fragment
227 ///     (implies that no prologue is present, and prologue processing should be
228 ///     skipped)
229 /// Epilogue Count : 5-bit field that differs in meaning based on the E field.
230 ///
231 ///                  If E is set, then this field specifies the index of the
232 ///                  first unwind code describing the (only) epilogue.
233 ///
234 ///                  Otherwise, this field indicates the number of exception
235 ///                  scopes.  If more than 31 scopes exist, then this field and
236 ///                  the Code Words field must both be set to 0 to indicate that
237 ///                  an extension word is required.
238 /// Code Words : 4-bit field that species the number of 32-bit words needed to
239 ///              contain all the unwind codes.  If more than 15 words (63 code
240 ///              bytes) are required, then this field and the Epilogue Count
241 ///              field must both be set to 0 to indicate that an extension word
242 ///              is required.
243 /// Extended Epilogue Count, Extended Code Words :
244 ///                          Valid only if Epilog Count and Code Words are both
245 ///                          set to 0.  Provides an 8-bit extended code word
246 ///                          count and 16-bits for epilogue count
247 ///
248 ///  3 3 2 2 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0
249 ///  1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0
250 /// +----------------+------+---+---+-------------------------------+
251 /// |  Ep Start Idx  | Cond |Res|       Epilogue Start Offset       |
252 /// +----------------+------+---+-----------------------------------+
253 ///
254 /// If the E bit is unset in the header, the header is followed by a series of
255 /// epilogue scopes, which are sorted by their offset.
256 ///
257 /// Epilogue Start Offset: 18-bit field encoding the offset of epilogue relative
258 ///                        to the start of the function in bytes divided by two
259 /// Res : 2-bit field reserved for future expansion (must be set to 0)
260 /// Condition : 4-bit field providing the condition under which the epilogue is
261 ///             executed.  Unconditional epilogues should set this field to 0xe.
262 ///             Epilogues must be entirely conditional or unconditional, and in
263 ///             Thumb-2 mode.  The epilogue beings with the first instruction
264 ///             after the IT opcode.
265 /// Epilogue Start Index : 8-bit field indicating the byte index of the first
266 ///                        unwind code describing the epilogue
267 ///
268 ///  3 3 2 2 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0
269 ///  1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0
270 /// +---------------+---------------+---------------+---------------+
271 /// | Unwind Code 3 | Unwind Code 2 | Unwind Code 1 | Unwind Code 0 |
272 /// +---------------+---------------+---------------+---------------+
273 ///
274 /// Following the epilogue scopes, the byte code describing the unwinding
275 /// follows.  This is padded to align up to word alignment.  Bytes are stored in
276 /// little endian.
277 ///
278 ///  3 3 2 2 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0
279 ///  1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0
280 /// +---------------------------------------------------------------+
281 /// |           Exception Handler RVA (requires X = 1)              |
282 /// +---------------------------------------------------------------+
283 /// |  (possibly followed by data required for exception handler)   |
284 /// +---------------------------------------------------------------+
285 ///
286 /// If the X bit is set in the header, the unwind byte code is followed by the
287 /// exception handler information.  This constants of one Exception Handler RVA
288 /// which is the address to the exception handler, followed immediately by the
289 /// variable length data associated with the exception handler.
290 ///
291 
292 struct EpilogueScope {
293   const support::ulittle32_t ES;
294 
EpilogueScopeEpilogueScope295   EpilogueScope(const support::ulittle32_t Data) : ES(Data) {}
EpilogueStartOffsetEpilogueScope296   uint32_t EpilogueStartOffset() const {
297     return (ES & 0x0003ffff);
298   }
ResEpilogueScope299   uint8_t Res() const {
300     return ((ES & 0x000c0000) >> 18);
301   }
ConditionEpilogueScope302   uint8_t Condition() const {
303     return ((ES & 0x00f00000) >> 20);
304   }
EpilogueStartIndexEpilogueScope305   uint8_t EpilogueStartIndex() const {
306     return ((ES & 0xff000000) >> 24);
307   }
308 };
309 
310 struct ExceptionDataRecord;
311 inline size_t HeaderWords(const ExceptionDataRecord &XR);
312 
313 struct ExceptionDataRecord {
314   const support::ulittle32_t *Data;
315 
ExceptionDataRecordExceptionDataRecord316   ExceptionDataRecord(const support::ulittle32_t *Data) : Data(Data) {}
317 
FunctionLengthExceptionDataRecord318   uint32_t FunctionLength() const {
319     return (Data[0] & 0x0003ffff);
320   }
321 
VersExceptionDataRecord322   uint8_t Vers() const {
323     return (Data[0] & 0x000C0000) >> 18;
324   }
325 
XExceptionDataRecord326   bool X() const {
327     return ((Data[0] & 0x00100000) >> 20);
328   }
329 
EExceptionDataRecord330   bool E() const {
331     return ((Data[0] & 0x00200000) >> 21);
332   }
333 
FExceptionDataRecord334   bool F() const {
335     return ((Data[0] & 0x00400000) >> 22);
336   }
337 
EpilogueCountExceptionDataRecord338   uint8_t EpilogueCount() const {
339     if (HeaderWords(*this) == 1)
340       return (Data[0] & 0x0f800000) >> 23;
341     return Data[1] & 0x0000ffff;
342   }
343 
CodeWordsExceptionDataRecord344   uint8_t CodeWords() const {
345     if (HeaderWords(*this) == 1)
346       return (Data[0] & 0xf0000000) >> 28;
347     return (Data[1] & 0x00ff0000) >> 16;
348   }
349 
EpilogueScopesExceptionDataRecord350   ArrayRef<support::ulittle32_t> EpilogueScopes() const {
351     assert(E() == 0 && "epilogue scopes are only present when the E bit is 0");
352     size_t Offset = HeaderWords(*this);
353     return makeArrayRef(&Data[Offset], EpilogueCount());
354   }
355 
UnwindByteCodeExceptionDataRecord356   ArrayRef<uint8_t> UnwindByteCode() const {
357     const size_t Offset = HeaderWords(*this)
358                         + (E() ? 0 :  EpilogueCount());
359     const uint8_t *ByteCode =
360       reinterpret_cast<const uint8_t *>(&Data[Offset]);
361     return makeArrayRef(ByteCode, CodeWords() * sizeof(uint32_t));
362   }
363 
ExceptionHandlerRVAExceptionDataRecord364   uint32_t ExceptionHandlerRVA() const {
365     assert(X() && "Exception Handler RVA is only valid if the X bit is set");
366     return Data[HeaderWords(*this) + EpilogueCount() + CodeWords()];
367   }
368 
ExceptionHandlerParameterExceptionDataRecord369   uint32_t ExceptionHandlerParameter() const {
370     assert(X() && "Exception Handler RVA is only valid if the X bit is set");
371     return Data[HeaderWords(*this) + EpilogueCount() + CodeWords() + 1];
372   }
373 };
374 
HeaderWords(const ExceptionDataRecord & XR)375 inline size_t HeaderWords(const ExceptionDataRecord &XR) {
376   return (XR.Data[0] & 0xff800000) ? 1 : 2;
377 }
378 }
379 }
380 }
381 
382 #endif
383