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[yaml2obj] [MachO] Fill Segment and Section data

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This fills section data with 0xDEADBEEF and segment data not inside a section with 0xBAADDA7A. This results in yaml2obj generating a matching size object file. Any additional bytes in the file are zero'd.

This is a starting point for populating the remaining segment data, and provides a hex viewable file that you can easily see the missing data in.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@270286 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Bieneman 2016-05-20 22:31:50 +00:00
parent 85b08a7199
commit d60c9c7025
1 changed files with 61 additions and 7 deletions
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68
tools/yaml2obj/yaml2macho.cpp
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@ -25,7 +25,7 @@ namespace {
class MachOWriter {
public:
MachOWriter(MachOYAML::Object &Obj) : Obj(Obj) {
MachOWriter(MachOYAML::Object &Obj) : Obj(Obj), is64Bit(true), fileStart(0) {
is64Bit = Obj.Header.magic == MachO::MH_MAGIC_64 ||
Obj.Header.magic == MachO::MH_CIGAM_64;
memset(reinterpret_cast<void *>(&Header64), 0,
@ -41,9 +41,11 @@ public:
private:
Error writeHeader(raw_ostream &OS);
Error writeLoadCommands(raw_ostream &OS);
Error writeSectionData(raw_ostream &OS);
MachOYAML::Object &Obj;
bool is64Bit;
uint64_t fileStart;
union {
MachO::mach_header_64 Header64;
@ -52,10 +54,13 @@ private:
};
Error MachOWriter::writeMachO(raw_ostream &OS) {
fileStart = OS.tell();
if (auto Err = writeHeader(OS))
return Err;
if (auto Err = writeLoadCommands(OS))
return Err;
if (auto Err = writeSectionData(OS))
return Err;
return Error::success();
}
@ -148,6 +153,18 @@ size_t writeLoadCommandData<MachO::dylinker_command>(MachOYAML::LoadCommand &LC,
return writePayloadString(LC, OS);
}
void ZeroFillBytes(raw_ostream &OS, size_t Size) {
std::vector<uint8_t> FillData;
FillData.insert(FillData.begin(), Size, 0);
OS.write(reinterpret_cast<char *>(FillData.data()), Size);
}
void Fill(raw_ostream &OS, size_t Size, uint32_t Data) {
std::vector<uint32_t> FillData;
FillData.insert(FillData.begin(), (Size / 4) + 1, Data);
OS.write(reinterpret_cast<char *>(FillData.data()), Size);
}
Error MachOWriter::writeLoadCommands(raw_ostream &OS) {
for (auto &LC : Obj.LoadCommands) {
size_t BytesWritten = 0;
@ -176,9 +193,7 @@ Error MachOWriter::writeLoadCommands(raw_ostream &OS) {
}
if (LC.ZeroPadBytes > 0) {
std::vector<uint8_t> FillData;
FillData.insert(FillData.begin(), LC.ZeroPadBytes, 0);
OS.write(reinterpret_cast<char *>(FillData.data()), LC.ZeroPadBytes);
ZeroFillBytes(OS, LC.ZeroPadBytes);
BytesWritten += LC.ZeroPadBytes;
}
@ -186,9 +201,48 @@ Error MachOWriter::writeLoadCommands(raw_ostream &OS) {
// specified test cases.
auto BytesRemaining = LC.Data.load_command_data.cmdsize - BytesWritten;
if (BytesRemaining > 0) {
std::vector<uint32_t> FillData;
FillData.insert(FillData.begin(), BytesRemaining, 0);
OS.write(reinterpret_cast<char *>(FillData.data()), BytesRemaining);
ZeroFillBytes(OS, BytesRemaining);
}
}
return Error::success();
}
Error MachOWriter::writeSectionData(raw_ostream &OS) {
for (auto &LC : Obj.LoadCommands) {
switch (LC.Data.load_command_data.cmd) {
case MachO::LC_SEGMENT:
case MachO::LC_SEGMENT_64:
uint64_t segOff = is64Bit ? LC.Data.segment_command_64_data.fileoff
: LC.Data.segment_command_data.fileoff;
// Zero Fill any data between the end of the last thing we wrote and the
// start of this section.
auto currOffset = OS.tell() - fileStart;
if (currOffset < segOff) {
ZeroFillBytes(OS, segOff - currOffset);
}
for (auto &Sec : LC.Sections) {
// Zero Fill any data between the end of the last thing we wrote and the
// start of this section.
assert(OS.tell() - fileStart <= Sec.offset &&
"Wrote too much data somewhere, section offsets don't line up.");
currOffset = OS.tell() - fileStart;
if (currOffset < Sec.offset) {
ZeroFillBytes(OS, Sec.offset - currOffset);
}
// Fills section data with 0xDEADBEEF
Fill(OS, Sec.size, 0xDEADBEEFu);
}
uint64_t segSize = is64Bit ? LC.Data.segment_command_64_data.filesize
: LC.Data.segment_command_data.filesize;
currOffset = OS.tell() - fileStart;
if (currOffset < segOff + segSize) {
// Fills segment data not covered by a section with 0xBAADDA7A
Fill(OS, (segOff + segSize) - currOffset, 0xBAADDA7Au);
}
break;
}
}
return Error::success();