xref: /llvm-project/lldb/source/Expression/IRMemoryMap.cpp (revision 0642cd768b80665585c8500bed2933a3b99123dc)
1 //===-- IRMemoryMap.cpp ---------------------------------------------------===//
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 #include "lldb/Expression/IRMemoryMap.h"
10 #include "lldb/Target/MemoryRegionInfo.h"
11 #include "lldb/Target/Process.h"
12 #include "lldb/Target/Target.h"
13 #include "lldb/Utility/DataBufferHeap.h"
14 #include "lldb/Utility/DataExtractor.h"
15 #include "lldb/Utility/LLDBAssert.h"
16 #include "lldb/Utility/LLDBLog.h"
17 #include "lldb/Utility/Log.h"
18 #include "lldb/Utility/Scalar.h"
19 #include "lldb/Utility/Status.h"
20 
21 using namespace lldb_private;
22 
23 IRMemoryMap::IRMemoryMap(lldb::TargetSP target_sp) : m_target_wp(target_sp) {
24   if (target_sp)
25     m_process_wp = target_sp->GetProcessSP();
26 }
27 
28 IRMemoryMap::~IRMemoryMap() {
29   lldb::ProcessSP process_sp = m_process_wp.lock();
30 
31   if (process_sp) {
32     AllocationMap::iterator iter;
33 
34     Status err;
35 
36     while ((iter = m_allocations.begin()) != m_allocations.end()) {
37       err.Clear();
38       if (iter->second.m_leak)
39         m_allocations.erase(iter);
40       else
41         Free(iter->first, err);
42     }
43   }
44 }
45 
46 lldb::addr_t IRMemoryMap::FindSpace(size_t size) {
47   // The FindSpace algorithm's job is to find a region of memory that the
48   // underlying process is unlikely to be using.
49   //
50   // The memory returned by this function will never be written to.  The only
51   // point is that it should not shadow process memory if possible, so that
52   // expressions processing real values from the process do not use the wrong
53   // data.
54   //
55   // If the process can in fact allocate memory (CanJIT() lets us know this)
56   // then this can be accomplished just be allocating memory in the inferior.
57   // Then no guessing is required.
58 
59   lldb::TargetSP target_sp = m_target_wp.lock();
60   lldb::ProcessSP process_sp = m_process_wp.lock();
61 
62   const bool process_is_alive = process_sp && process_sp->IsAlive();
63 
64   lldb::addr_t ret = LLDB_INVALID_ADDRESS;
65   if (size == 0)
66     return ret;
67 
68   if (process_is_alive && process_sp->CanJIT()) {
69     Status alloc_error;
70 
71     ret = process_sp->AllocateMemory(size, lldb::ePermissionsReadable |
72                                                lldb::ePermissionsWritable,
73                                      alloc_error);
74 
75     if (!alloc_error.Success())
76       return LLDB_INVALID_ADDRESS;
77     else
78       return ret;
79   }
80 
81   // At this point we know that we need to hunt.
82   //
83   // First, go to the end of the existing allocations we've made if there are
84   // any allocations.  Otherwise start at the beginning of memory.
85 
86   if (m_allocations.empty()) {
87     ret = 0;
88   } else {
89     auto back = m_allocations.rbegin();
90     lldb::addr_t addr = back->first;
91     size_t alloc_size = back->second.m_size;
92     ret = llvm::alignTo(addr + alloc_size, 4096);
93   }
94 
95   uint64_t end_of_memory;
96   switch (GetAddressByteSize()) {
97   case 2:
98     end_of_memory = 0xffffull;
99     break;
100   case 4:
101     end_of_memory = 0xffffffffull;
102     break;
103   case 8:
104     end_of_memory = 0xffffffffffffffffull;
105     break;
106   default:
107     lldbassert(false && "Invalid address size.");
108     return LLDB_INVALID_ADDRESS;
109   }
110 
111   // Now, if it's possible to use the GetMemoryRegionInfo API to detect mapped
112   // regions, walk forward through memory until a region is found that has
113   // adequate space for our allocation.
114   if (process_is_alive) {
115     MemoryRegionInfo region_info;
116     Status err = process_sp->GetMemoryRegionInfo(ret, region_info);
117     if (err.Success()) {
118       while (true) {
119         if (region_info.GetRange().GetRangeBase() == 0 &&
120             region_info.GetRange().GetRangeEnd() < end_of_memory) {
121           // Don't use a region that starts at address 0,
122           // it can make it harder to debug null dereference crashes
123           // in the inferior.
124           ret = region_info.GetRange().GetRangeEnd();
125         } else if (region_info.GetReadable() !=
126                        MemoryRegionInfo::OptionalBool::eNo ||
127                    region_info.GetWritable() !=
128                        MemoryRegionInfo::OptionalBool::eNo ||
129                    region_info.GetExecutable() !=
130                        MemoryRegionInfo::OptionalBool::eNo) {
131           if (region_info.GetRange().GetRangeEnd() - 1 >= end_of_memory) {
132             ret = LLDB_INVALID_ADDRESS;
133             break;
134           } else {
135             ret = region_info.GetRange().GetRangeEnd();
136           }
137         } else if (ret + size < region_info.GetRange().GetRangeEnd()) {
138           return ret;
139         } else {
140           // ret stays the same.  We just need to walk a bit further.
141         }
142 
143         err = process_sp->GetMemoryRegionInfo(
144             region_info.GetRange().GetRangeEnd(), region_info);
145         if (err.Fail()) {
146           lldbassert(0 && "GetMemoryRegionInfo() succeeded, then failed");
147           ret = LLDB_INVALID_ADDRESS;
148           break;
149         }
150       }
151     }
152   }
153 
154   // We've tried our algorithm, and it didn't work.  Now we have to reset back
155   // to the end of the allocations we've already reported, or use a 'sensible'
156   // default if this is our first allocation.
157   if (m_allocations.empty()) {
158     uint64_t alloc_address = target_sp->GetExprAllocAddress();
159     if (alloc_address > 0) {
160       if (alloc_address >= end_of_memory) {
161         lldbassert(0 && "The allocation address for expression evaluation must "
162                         "be within process address space");
163         return LLDB_INVALID_ADDRESS;
164       }
165       ret = alloc_address;
166     } else {
167       uint32_t address_byte_size = GetAddressByteSize();
168       if (address_byte_size != UINT32_MAX) {
169         switch (address_byte_size) {
170         case 2:
171           ret = 0x8000ull;
172           break;
173         case 4:
174           ret = 0xee000000ull;
175           break;
176         case 8:
177           ret = 0xdead0fff00000000ull;
178           break;
179         default:
180           lldbassert(false && "Invalid address size.");
181           return LLDB_INVALID_ADDRESS;
182         }
183       }
184     }
185   } else {
186     auto back = m_allocations.rbegin();
187     lldb::addr_t addr = back->first;
188     size_t alloc_size = back->second.m_size;
189     uint64_t align = target_sp->GetExprAllocAlign();
190     if (align == 0)
191       align = 4096;
192     ret = llvm::alignTo(addr + alloc_size, align);
193   }
194 
195   return ret;
196 }
197 
198 IRMemoryMap::AllocationMap::iterator
199 IRMemoryMap::FindAllocation(lldb::addr_t addr, size_t size) {
200   if (addr == LLDB_INVALID_ADDRESS)
201     return m_allocations.end();
202 
203   AllocationMap::iterator iter = m_allocations.lower_bound(addr);
204 
205   if (iter == m_allocations.end() || iter->first > addr) {
206     if (iter == m_allocations.begin())
207       return m_allocations.end();
208     iter--;
209   }
210 
211   if (iter->first <= addr && iter->first + iter->second.m_size >= addr + size)
212     return iter;
213 
214   return m_allocations.end();
215 }
216 
217 bool IRMemoryMap::IntersectsAllocation(lldb::addr_t addr, size_t size) const {
218   if (addr == LLDB_INVALID_ADDRESS)
219     return false;
220 
221   AllocationMap::const_iterator iter = m_allocations.lower_bound(addr);
222 
223   // Since we only know that the returned interval begins at a location greater
224   // than or equal to where the given interval begins, it's possible that the
225   // given interval intersects either the returned interval or the previous
226   // interval.  Thus, we need to check both. Note that we only need to check
227   // these two intervals.  Since all intervals are disjoint it is not possible
228   // that an adjacent interval does not intersect, but a non-adjacent interval
229   // does intersect.
230   if (iter != m_allocations.end()) {
231     if (AllocationsIntersect(addr, size, iter->second.m_process_start,
232                              iter->second.m_size))
233       return true;
234   }
235 
236   if (iter != m_allocations.begin()) {
237     --iter;
238     if (AllocationsIntersect(addr, size, iter->second.m_process_start,
239                              iter->second.m_size))
240       return true;
241   }
242 
243   return false;
244 }
245 
246 bool IRMemoryMap::AllocationsIntersect(lldb::addr_t addr1, size_t size1,
247                                        lldb::addr_t addr2, size_t size2) {
248   // Given two half open intervals [A, B) and [X, Y), the only 6 permutations
249   // that satisfy A<B and X<Y are the following:
250   // A B X Y
251   // A X B Y  (intersects)
252   // A X Y B  (intersects)
253   // X A B Y  (intersects)
254   // X A Y B  (intersects)
255   // X Y A B
256   // The first is B <= X, and the last is Y <= A. So the condition is !(B <= X
257   // || Y <= A)), or (X < B && A < Y)
258   return (addr2 < (addr1 + size1)) && (addr1 < (addr2 + size2));
259 }
260 
261 lldb::ByteOrder IRMemoryMap::GetByteOrder() {
262   lldb::ProcessSP process_sp = m_process_wp.lock();
263 
264   if (process_sp)
265     return process_sp->GetByteOrder();
266 
267   lldb::TargetSP target_sp = m_target_wp.lock();
268 
269   if (target_sp)
270     return target_sp->GetArchitecture().GetByteOrder();
271 
272   return lldb::eByteOrderInvalid;
273 }
274 
275 uint32_t IRMemoryMap::GetAddressByteSize() {
276   lldb::ProcessSP process_sp = m_process_wp.lock();
277 
278   if (process_sp)
279     return process_sp->GetAddressByteSize();
280 
281   lldb::TargetSP target_sp = m_target_wp.lock();
282 
283   if (target_sp)
284     return target_sp->GetArchitecture().GetAddressByteSize();
285 
286   return UINT32_MAX;
287 }
288 
289 ExecutionContextScope *IRMemoryMap::GetBestExecutionContextScope() const {
290   lldb::ProcessSP process_sp = m_process_wp.lock();
291 
292   if (process_sp)
293     return process_sp.get();
294 
295   lldb::TargetSP target_sp = m_target_wp.lock();
296 
297   if (target_sp)
298     return target_sp.get();
299 
300   return nullptr;
301 }
302 
303 IRMemoryMap::Allocation::Allocation(lldb::addr_t process_alloc,
304                                     lldb::addr_t process_start, size_t size,
305                                     uint32_t permissions, uint8_t alignment,
306                                     AllocationPolicy policy)
307     : m_process_alloc(process_alloc), m_process_start(process_start),
308       m_size(size), m_policy(policy), m_leak(false), m_permissions(permissions),
309       m_alignment(alignment) {
310   switch (policy) {
311   default:
312     llvm_unreachable("Invalid AllocationPolicy");
313   case eAllocationPolicyHostOnly:
314   case eAllocationPolicyMirror:
315     m_data.SetByteSize(size);
316     break;
317   case eAllocationPolicyProcessOnly:
318     break;
319   }
320 }
321 
322 lldb::addr_t IRMemoryMap::Malloc(size_t size, uint8_t alignment,
323                                  uint32_t permissions, AllocationPolicy policy,
324                                  bool zero_memory, Status &error) {
325   lldb_private::Log *log(GetLog(LLDBLog::Expressions));
326   error.Clear();
327 
328   lldb::ProcessSP process_sp;
329   lldb::addr_t allocation_address = LLDB_INVALID_ADDRESS;
330   lldb::addr_t aligned_address = LLDB_INVALID_ADDRESS;
331 
332   size_t allocation_size;
333 
334   if (size == 0) {
335     // FIXME: Malloc(0) should either return an invalid address or assert, in
336     // order to cut down on unnecessary allocations.
337     allocation_size = alignment;
338   } else {
339     // Round up the requested size to an aligned value.
340     allocation_size = llvm::alignTo(size, alignment);
341 
342     // The process page cache does not see the requested alignment. We can't
343     // assume its result will be any more than 1-byte aligned. To work around
344     // this, request `alignment - 1` additional bytes.
345     allocation_size += alignment - 1;
346   }
347 
348   switch (policy) {
349   default:
350     error =
351         Status::FromErrorString("Couldn't malloc: invalid allocation policy");
352     return LLDB_INVALID_ADDRESS;
353   case eAllocationPolicyHostOnly:
354     allocation_address = FindSpace(allocation_size);
355     if (allocation_address == LLDB_INVALID_ADDRESS) {
356       error = Status::FromErrorString("Couldn't malloc: address space is full");
357       return LLDB_INVALID_ADDRESS;
358     }
359     break;
360   case eAllocationPolicyMirror:
361     process_sp = m_process_wp.lock();
362     LLDB_LOGF(log,
363               "IRMemoryMap::%s process_sp=0x%" PRIxPTR
364               ", process_sp->CanJIT()=%s, process_sp->IsAlive()=%s",
365               __FUNCTION__, reinterpret_cast<uintptr_t>(process_sp.get()),
366               process_sp && process_sp->CanJIT() ? "true" : "false",
367               process_sp && process_sp->IsAlive() ? "true" : "false");
368     if (process_sp && process_sp->CanJIT() && process_sp->IsAlive()) {
369       if (!zero_memory)
370         allocation_address =
371             process_sp->AllocateMemory(allocation_size, permissions, error);
372       else
373         allocation_address =
374             process_sp->CallocateMemory(allocation_size, permissions, error);
375 
376       if (!error.Success())
377         return LLDB_INVALID_ADDRESS;
378     } else {
379       LLDB_LOGF(log,
380                 "IRMemoryMap::%s switching to eAllocationPolicyHostOnly "
381                 "due to failed condition (see previous expr log message)",
382                 __FUNCTION__);
383       policy = eAllocationPolicyHostOnly;
384       allocation_address = FindSpace(allocation_size);
385       if (allocation_address == LLDB_INVALID_ADDRESS) {
386         error =
387             Status::FromErrorString("Couldn't malloc: address space is full");
388         return LLDB_INVALID_ADDRESS;
389       }
390     }
391     break;
392   case eAllocationPolicyProcessOnly:
393     process_sp = m_process_wp.lock();
394     if (process_sp) {
395       if (process_sp->CanJIT() && process_sp->IsAlive()) {
396         if (!zero_memory)
397           allocation_address =
398               process_sp->AllocateMemory(allocation_size, permissions, error);
399         else
400           allocation_address =
401               process_sp->CallocateMemory(allocation_size, permissions, error);
402 
403         if (!error.Success())
404           return LLDB_INVALID_ADDRESS;
405       } else {
406         error = Status::FromErrorString(
407             "Couldn't malloc: process doesn't support allocating memory");
408         return LLDB_INVALID_ADDRESS;
409       }
410     } else {
411       error = Status::FromErrorString(
412           "Couldn't malloc: process doesn't exist, and this "
413           "memory must be in the process");
414       return LLDB_INVALID_ADDRESS;
415     }
416     break;
417   }
418 
419   lldb::addr_t mask = alignment - 1;
420   aligned_address = (allocation_address + mask) & (~mask);
421 
422   m_allocations.emplace(
423       std::piecewise_construct, std::forward_as_tuple(aligned_address),
424       std::forward_as_tuple(allocation_address, aligned_address,
425                             allocation_size, permissions, alignment, policy));
426 
427   if (zero_memory) {
428     Status write_error;
429     std::vector<uint8_t> zero_buf(size, 0);
430     WriteMemory(aligned_address, zero_buf.data(), size, write_error);
431   }
432 
433   if (log) {
434     const char *policy_string;
435 
436     switch (policy) {
437     default:
438       policy_string = "<invalid policy>";
439       break;
440     case eAllocationPolicyHostOnly:
441       policy_string = "eAllocationPolicyHostOnly";
442       break;
443     case eAllocationPolicyProcessOnly:
444       policy_string = "eAllocationPolicyProcessOnly";
445       break;
446     case eAllocationPolicyMirror:
447       policy_string = "eAllocationPolicyMirror";
448       break;
449     }
450 
451     LLDB_LOGF(log,
452               "IRMemoryMap::Malloc (%" PRIu64 ", 0x%" PRIx64 ", 0x%" PRIx64
453               ", %s) -> 0x%" PRIx64,
454               (uint64_t)allocation_size, (uint64_t)alignment,
455               (uint64_t)permissions, policy_string, aligned_address);
456   }
457 
458   return aligned_address;
459 }
460 
461 void IRMemoryMap::Leak(lldb::addr_t process_address, Status &error) {
462   error.Clear();
463 
464   AllocationMap::iterator iter = m_allocations.find(process_address);
465 
466   if (iter == m_allocations.end()) {
467     error = Status::FromErrorString("Couldn't leak: allocation doesn't exist");
468     return;
469   }
470 
471   Allocation &allocation = iter->second;
472 
473   allocation.m_leak = true;
474 }
475 
476 void IRMemoryMap::Free(lldb::addr_t process_address, Status &error) {
477   error.Clear();
478 
479   AllocationMap::iterator iter = m_allocations.find(process_address);
480 
481   if (iter == m_allocations.end()) {
482     error = Status::FromErrorString("Couldn't free: allocation doesn't exist");
483     return;
484   }
485 
486   Allocation &allocation = iter->second;
487 
488   switch (allocation.m_policy) {
489   default:
490   case eAllocationPolicyHostOnly: {
491     lldb::ProcessSP process_sp = m_process_wp.lock();
492     if (process_sp) {
493       if (process_sp->CanJIT() && process_sp->IsAlive())
494         process_sp->DeallocateMemory(
495             allocation.m_process_alloc); // FindSpace allocated this for real
496     }
497 
498     break;
499   }
500   case eAllocationPolicyMirror:
501   case eAllocationPolicyProcessOnly: {
502     lldb::ProcessSP process_sp = m_process_wp.lock();
503     if (process_sp)
504       process_sp->DeallocateMemory(allocation.m_process_alloc);
505   }
506   }
507 
508   if (lldb_private::Log *log = GetLog(LLDBLog::Expressions)) {
509     LLDB_LOGF(log,
510               "IRMemoryMap::Free (0x%" PRIx64 ") freed [0x%" PRIx64
511               "..0x%" PRIx64 ")",
512               (uint64_t)process_address, iter->second.m_process_start,
513               iter->second.m_process_start + iter->second.m_size);
514   }
515 
516   m_allocations.erase(iter);
517 }
518 
519 bool IRMemoryMap::GetAllocSize(lldb::addr_t address, size_t &size) {
520   AllocationMap::iterator iter = FindAllocation(address, size);
521   if (iter == m_allocations.end())
522     return false;
523 
524   Allocation &al = iter->second;
525 
526   if (address > (al.m_process_start + al.m_size)) {
527     size = 0;
528     return false;
529   }
530 
531   if (address > al.m_process_start) {
532     int dif = address - al.m_process_start;
533     size = al.m_size - dif;
534     return true;
535   }
536 
537   size = al.m_size;
538   return true;
539 }
540 
541 void IRMemoryMap::WriteMemory(lldb::addr_t process_address,
542                               const uint8_t *bytes, size_t size,
543                               Status &error) {
544   error.Clear();
545 
546   AllocationMap::iterator iter = FindAllocation(process_address, size);
547 
548   if (iter == m_allocations.end()) {
549     lldb::ProcessSP process_sp = m_process_wp.lock();
550 
551     if (process_sp) {
552       process_sp->WriteMemory(process_address, bytes, size, error);
553       return;
554     }
555 
556     error = Status::FromErrorString(
557         "Couldn't write: no allocation contains the target "
558         "range and the process doesn't exist");
559     return;
560   }
561 
562   Allocation &allocation = iter->second;
563 
564   uint64_t offset = process_address - allocation.m_process_start;
565 
566   lldb::ProcessSP process_sp;
567 
568   switch (allocation.m_policy) {
569   default:
570     error =
571         Status::FromErrorString("Couldn't write: invalid allocation policy");
572     return;
573   case eAllocationPolicyHostOnly:
574     if (!allocation.m_data.GetByteSize()) {
575       error = Status::FromErrorString("Couldn't write: data buffer is empty");
576       return;
577     }
578     ::memcpy(allocation.m_data.GetBytes() + offset, bytes, size);
579     break;
580   case eAllocationPolicyMirror:
581     if (!allocation.m_data.GetByteSize()) {
582       error = Status::FromErrorString("Couldn't write: data buffer is empty");
583       return;
584     }
585     ::memcpy(allocation.m_data.GetBytes() + offset, bytes, size);
586     process_sp = m_process_wp.lock();
587     if (process_sp) {
588       process_sp->WriteMemory(process_address, bytes, size, error);
589       if (!error.Success())
590         return;
591     }
592     break;
593   case eAllocationPolicyProcessOnly:
594     process_sp = m_process_wp.lock();
595     if (process_sp) {
596       process_sp->WriteMemory(process_address, bytes, size, error);
597       if (!error.Success())
598         return;
599     }
600     break;
601   }
602 
603   if (lldb_private::Log *log = GetLog(LLDBLog::Expressions)) {
604     LLDB_LOGF(log,
605               "IRMemoryMap::WriteMemory (0x%" PRIx64 ", 0x%" PRIxPTR
606               ", 0x%" PRId64 ") went to [0x%" PRIx64 "..0x%" PRIx64 ")",
607               (uint64_t)process_address, reinterpret_cast<uintptr_t>(bytes), (uint64_t)size,
608               (uint64_t)allocation.m_process_start,
609               (uint64_t)allocation.m_process_start +
610                   (uint64_t)allocation.m_size);
611   }
612 }
613 
614 void IRMemoryMap::WriteScalarToMemory(lldb::addr_t process_address,
615                                       Scalar &scalar, size_t size,
616                                       Status &error) {
617   error.Clear();
618 
619   if (size == UINT32_MAX)
620     size = scalar.GetByteSize();
621 
622   if (size > 0) {
623     uint8_t buf[32];
624     const size_t mem_size =
625         scalar.GetAsMemoryData(buf, size, GetByteOrder(), error);
626     if (mem_size > 0) {
627       return WriteMemory(process_address, buf, mem_size, error);
628     } else {
629       error = Status::FromErrorString(
630           "Couldn't write scalar: failed to get scalar as memory data");
631     }
632   } else {
633     error = Status::FromErrorString("Couldn't write scalar: its size was zero");
634   }
635 }
636 
637 void IRMemoryMap::WritePointerToMemory(lldb::addr_t process_address,
638                                        lldb::addr_t address, Status &error) {
639   error.Clear();
640 
641   Scalar scalar(address);
642 
643   WriteScalarToMemory(process_address, scalar, GetAddressByteSize(), error);
644 }
645 
646 void IRMemoryMap::ReadMemory(uint8_t *bytes, lldb::addr_t process_address,
647                              size_t size, Status &error) {
648   error.Clear();
649 
650   AllocationMap::iterator iter = FindAllocation(process_address, size);
651 
652   if (iter == m_allocations.end()) {
653     lldb::ProcessSP process_sp = m_process_wp.lock();
654 
655     if (process_sp) {
656       process_sp->ReadMemory(process_address, bytes, size, error);
657       return;
658     }
659 
660     lldb::TargetSP target_sp = m_target_wp.lock();
661 
662     if (target_sp) {
663       Address absolute_address(process_address);
664       target_sp->ReadMemory(absolute_address, bytes, size, error, true);
665       return;
666     }
667 
668     error = Status::FromErrorString(
669         "Couldn't read: no allocation contains the target "
670         "range, and neither the process nor the target exist");
671     return;
672   }
673 
674   Allocation &allocation = iter->second;
675 
676   uint64_t offset = process_address - allocation.m_process_start;
677 
678   if (offset > allocation.m_size) {
679     error =
680         Status::FromErrorString("Couldn't read: data is not in the allocation");
681     return;
682   }
683 
684   lldb::ProcessSP process_sp;
685 
686   switch (allocation.m_policy) {
687   default:
688     error = Status::FromErrorString("Couldn't read: invalid allocation policy");
689     return;
690   case eAllocationPolicyHostOnly:
691     if (!allocation.m_data.GetByteSize()) {
692       error = Status::FromErrorString("Couldn't read: data buffer is empty");
693       return;
694     }
695     if (allocation.m_data.GetByteSize() < offset + size) {
696       error =
697           Status::FromErrorString("Couldn't read: not enough underlying data");
698       return;
699     }
700 
701     ::memcpy(bytes, allocation.m_data.GetBytes() + offset, size);
702     break;
703   case eAllocationPolicyMirror:
704     process_sp = m_process_wp.lock();
705     if (process_sp) {
706       process_sp->ReadMemory(process_address, bytes, size, error);
707       if (!error.Success())
708         return;
709     } else {
710       if (!allocation.m_data.GetByteSize()) {
711         error = Status::FromErrorString("Couldn't read: data buffer is empty");
712         return;
713       }
714       ::memcpy(bytes, allocation.m_data.GetBytes() + offset, size);
715     }
716     break;
717   case eAllocationPolicyProcessOnly:
718     process_sp = m_process_wp.lock();
719     if (process_sp) {
720       process_sp->ReadMemory(process_address, bytes, size, error);
721       if (!error.Success())
722         return;
723     }
724     break;
725   }
726 
727   if (lldb_private::Log *log = GetLog(LLDBLog::Expressions)) {
728     LLDB_LOGF(log,
729               "IRMemoryMap::ReadMemory (0x%" PRIx64 ", 0x%" PRIxPTR
730               ", 0x%" PRId64 ") came from [0x%" PRIx64 "..0x%" PRIx64 ")",
731               (uint64_t)process_address, reinterpret_cast<uintptr_t>(bytes), (uint64_t)size,
732               (uint64_t)allocation.m_process_start,
733               (uint64_t)allocation.m_process_start +
734                   (uint64_t)allocation.m_size);
735   }
736 }
737 
738 void IRMemoryMap::ReadScalarFromMemory(Scalar &scalar,
739                                        lldb::addr_t process_address,
740                                        size_t size, Status &error) {
741   error.Clear();
742 
743   if (size > 0) {
744     DataBufferHeap buf(size, 0);
745     ReadMemory(buf.GetBytes(), process_address, size, error);
746 
747     if (!error.Success())
748       return;
749 
750     DataExtractor extractor(buf.GetBytes(), buf.GetByteSize(), GetByteOrder(),
751                             GetAddressByteSize());
752 
753     lldb::offset_t offset = 0;
754 
755     switch (size) {
756     default:
757       error = Status::FromErrorStringWithFormat(
758           "Couldn't read scalar: unsupported size %" PRIu64, (uint64_t)size);
759       return;
760     case 1:
761       scalar = extractor.GetU8(&offset);
762       break;
763     case 2:
764       scalar = extractor.GetU16(&offset);
765       break;
766     case 4:
767       scalar = extractor.GetU32(&offset);
768       break;
769     case 8:
770       scalar = extractor.GetU64(&offset);
771       break;
772     }
773   } else {
774     error = Status::FromErrorString("Couldn't read scalar: its size was zero");
775   }
776 }
777 
778 void IRMemoryMap::ReadPointerFromMemory(lldb::addr_t *address,
779                                         lldb::addr_t process_address,
780                                         Status &error) {
781   error.Clear();
782 
783   Scalar pointer_scalar;
784   ReadScalarFromMemory(pointer_scalar, process_address, GetAddressByteSize(),
785                        error);
786 
787   if (!error.Success())
788     return;
789 
790   *address = pointer_scalar.ULongLong();
791 }
792 
793 void IRMemoryMap::GetMemoryData(DataExtractor &extractor,
794                                 lldb::addr_t process_address, size_t size,
795                                 Status &error) {
796   error.Clear();
797 
798   if (size > 0) {
799     AllocationMap::iterator iter = FindAllocation(process_address, size);
800 
801     if (iter == m_allocations.end()) {
802       error = Status::FromErrorStringWithFormat(
803           "Couldn't find an allocation containing [0x%" PRIx64 "..0x%" PRIx64
804           ")",
805           process_address, process_address + size);
806       return;
807     }
808 
809     Allocation &allocation = iter->second;
810 
811     switch (allocation.m_policy) {
812     default:
813       error = Status::FromErrorString(
814           "Couldn't get memory data: invalid allocation policy");
815       return;
816     case eAllocationPolicyProcessOnly:
817       error = Status::FromErrorString(
818           "Couldn't get memory data: memory is only in the target");
819       return;
820     case eAllocationPolicyMirror: {
821       lldb::ProcessSP process_sp = m_process_wp.lock();
822 
823       if (!allocation.m_data.GetByteSize()) {
824         error = Status::FromErrorString(
825             "Couldn't get memory data: data buffer is empty");
826         return;
827       }
828       if (process_sp) {
829         process_sp->ReadMemory(allocation.m_process_start,
830                                allocation.m_data.GetBytes(),
831                                allocation.m_data.GetByteSize(), error);
832         if (!error.Success())
833           return;
834         uint64_t offset = process_address - allocation.m_process_start;
835         extractor = DataExtractor(allocation.m_data.GetBytes() + offset, size,
836                                   GetByteOrder(), GetAddressByteSize());
837         return;
838       }
839     } break;
840     case eAllocationPolicyHostOnly:
841       if (!allocation.m_data.GetByteSize()) {
842         error = Status::FromErrorString(
843             "Couldn't get memory data: data buffer is empty");
844         return;
845       }
846       uint64_t offset = process_address - allocation.m_process_start;
847       extractor = DataExtractor(allocation.m_data.GetBytes() + offset, size,
848                                 GetByteOrder(), GetAddressByteSize());
849       return;
850     }
851   } else {
852     error =
853         Status::FromErrorString("Couldn't get memory data: its size was zero");
854     return;
855   }
856 }
857