Merge pull request swiftlang#38663 from augusto2112/read-macho-sections-together

Revert "Read machO sections section by section"

Author: fredriss

include/swift/Reflection/ReflectionContext.h

@@ -205,7 +205,36 @@ class ReflectionContext
       return false;
 
     auto Slide = ImageStart.getAddressData() - Command->vmaddr;
+    std::string Prefix = "__swift5";
+    uint64_t RangeStart = UINT64_MAX;
+    uint64_t RangeEnd = UINT64_MAX;
     auto SectionsBuf = reinterpret_cast<const char *>(Sections.get());
+    for (unsigned I = 0; I < NumSect; ++I) {
+      auto S = reinterpret_cast<typename T::Section *>(
+          SectionsBuf + (I * sizeof(typename T::Section)));
+      if (strncmp(S->sectname, Prefix.c_str(), strlen(Prefix.c_str())) != 0)
+        continue;
+      if (RangeStart == UINT64_MAX && RangeEnd == UINT64_MAX) {
+        RangeStart = S->addr + Slide;
+        RangeEnd = S->addr + S->size + Slide;
+        continue;
+      }
+      RangeStart = std::min(RangeStart, (uint64_t)S->addr + Slide);
+      RangeEnd = std::max(RangeEnd, (uint64_t)(S->addr + S->size + Slide));
+      // Keep the range rounded to 8 byte alignment on both ends so we don't
+      // introduce misaligned pointers mapping between local and remote
+      // address space.
+      RangeStart = RangeStart & ~7;
+      RangeEnd = RangeEnd + 7 & ~7;      
+    }
+ 
+    if (RangeStart == UINT64_MAX && RangeEnd == UINT64_MAX)
+      return false;
+
+    auto SectBuf = this->getReader().readBytes(RemoteAddress(RangeStart),
+                                               RangeEnd - RangeStart);
+    if (!SectBuf)
+      return false;
 
     auto findMachOSectionByName = [&](llvm::StringRef Name)
         -> std::pair<RemoteRef<void>, uint64_t> {
@@ -215,13 +244,11 @@ class ReflectionContext
         if (strncmp(S->sectname, Name.data(), strlen(Name.data())) != 0)
           continue;
         auto RemoteSecStart = S->addr + Slide;
-        auto LocalSectBuf =
-            this->getReader().readBytes(RemoteAddress(RemoteSecStart), S->size);
-        if (!LocalSectBuf)
-          return {nullptr, 0};
-
-        auto StartRef = RemoteRef<void>(RemoteSecStart, LocalSectBuf.get());
-        savedBuffers.push_back(std::move(LocalSectBuf));
+        auto SectBufData = reinterpret_cast<const char *>(SectBuf.get());
+        auto LocalSectStart =
+            reinterpret_cast<const char *>(SectBufData + RemoteSecStart - RangeStart);
+        
+        auto StartRef = RemoteRef<void>(RemoteSecStart, LocalSectStart);
         return {StartRef, S->size};
       }
       return {nullptr, 0};
@@ -280,6 +307,7 @@ class ReflectionContext
     }
 
     savedBuffers.push_back(std::move(Buf));
+    savedBuffers.push_back(std::move(SectBuf));
     savedBuffers.push_back(std::move(Sections));
     return true;
   }