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Another additional error check for invalid Mach-O files for the

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obsolete load commands.

Again the philosophy of the error checking in libObject for
Mach-O files, the idea behind the checking is that we never
will return a Mach-O file out of libObject that contains unknown
things the library code can’t operate on.  So known obsolete
load commands will cause a hard error.

Also to make things clear I have added comments to the
values and structures in Support/Mach-O.h and
Support/MachO.def as to what is obsolete.

As noted in a TODO in the code, there may need to be a
non-default mode to allow some unknown values for well
structured Mach-O files with things like unknown load
load commands.  So things like using an old lldb on a newer
Mach-O file could still provide some limited functionality.

llvm-svn: 285342
This commit is contained in:
Kevin Enderby
2016-10-27 20:59:10 +00:00
parent 58e14743ca
commit bc5c29a65f
12 changed files with 75 additions and 0 deletions
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26
llvm/lib/Object/MachOObjectFile.cpp
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@@ -912,6 +912,23 @@ static Error checkTwoLevelHintsCommand(const MachOObjectFile *Obj,
return Error::success();
}
// Returns true if the libObject code does not support the load command and its
// contents. The cmd value it is treated as an unknown load command but with
// an error message that says the cmd value is obsolete.
static bool isLoadCommandObsolete(uint32_t cmd) {
if (cmd == MachO::LC_SYMSEG ||
cmd == MachO::LC_LOADFVMLIB ||
cmd == MachO::LC_IDFVMLIB ||
cmd == MachO::LC_IDENT ||
cmd == MachO::LC_FVMFILE ||
cmd == MachO::LC_PREPAGE ||
cmd == MachO::LC_PREBOUND_DYLIB ||
cmd == MachO::LC_TWOLEVEL_HINTS ||
cmd == MachO::LC_PREBIND_CKSUM)
return true;
return false;
}
Expected<std::unique_ptr<MachOObjectFile>>
MachOObjectFile::create(MemoryBufferRef Object, bool IsLittleEndian,
bool Is64Bits, uint32_t UniversalCputype,
@@ -1250,11 +1267,20 @@ MachOObjectFile::MachOObjectFile(MemoryBufferRef Object, bool IsLittleEndian,
} else if (Load.C.cmd == MachO::LC_THREAD) {
if ((Err = checkThreadCommand(this, Load, I, "LC_THREAD")))
return;
// Note: LC_TWOLEVEL_HINTS is really obsolete and is not supported.
} else if (Load.C.cmd == MachO::LC_TWOLEVEL_HINTS) {
if ((Err = checkTwoLevelHintsCommand(this, Load, I,
&TwoLevelHintsLoadCmd)))
return;
} else if (isLoadCommandObsolete(Load.C.cmd)) {
Err = malformedError("load command " + Twine(I) + " for cmd value of: " +
Twine(Load.C.cmd) + " is obsolete and not "
"supported");
return;
}
// TODO: generate a error for unknown load commands by default. But still
// need work out an approach to allow or not allow unknown values like this
// as an option for some uses like lldb.
if (I < LoadCommandCount - 1) {
if (auto LoadOrErr = getNextLoadCommandInfo(this, I, Load))
Load = *LoadOrErr;