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Read machO sections section by section

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This changes how ReflectionContext reads machO reflection sections by reading them individually instead of as one big memory block spanning from the first to the last section (and including whatever else is in between). This change will enable an optimization on LLDB's side where, if we're reading read-only data, we read from the file-cache instead of the child process, which should speed up debugging when working with remote processes.
This commit is contained in:
Augusto Noronha
2021-04-23 14:16:50 -03:00
parent 0e5edd3d47
commit b54d42653e
1 changed files with 7 additions and 35 deletions
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42
include/swift/Reflection/ReflectionContext.h
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@@ -205,36 +205,7 @@ public:
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> {
@@ -244,11 +215,13 @@ public:
if (strncmp(S->sectname, Name.data(), strlen(Name.data())) != 0)
continue;
auto RemoteSecStart = S->addr + Slide;
auto SectBufData = reinterpret_cast<const char *>(SectBuf.get());
auto LocalSectStart =
reinterpret_cast<const char *>(SectBufData + RemoteSecStart - RangeStart);
auto StartRef = RemoteRef<void>(RemoteSecStart, LocalSectStart);
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));
return {StartRef, S->size};
}
return {nullptr, 0};
@@ -307,7 +280,6 @@ public:
}
savedBuffers.push_back(std::move(Buf));
savedBuffers.push_back(std::move(SectBuf));
savedBuffers.push_back(std::move(Sections));
return true;
}