jasonmolenda added inline comments.
================
Comment at:
lldb/source/Plugins/DynamicLoader/Darwin-Kernel/DynamicLoaderDarwinKernel.cpp:1093
+ // don't mark those as addressable.
+ m_process->SetVirtualAddressableBits((wordsize * 8) - 9);
+ addr_t sym_addr = symbol->GetLoadAddress(&m_process->GetTarget());
----------------
JDevlieghere wrote:
> Instead of changing the addressable bits for the process, should we modify
> `GetLoadAddress` to explicitly skip the stripping instead? This is probably
> purely theoretical, but what if another (host) thread tried to read memory in
> the meantime? Changing global state like this can lead to subtle bugs.
Yes, I thought about touching the global state. At this point we've just
attached to the remote device / corefile, and are loading the kernel binary.
There aren't other threads operating on this at this time. We're also in a
state where the number of addressable bits may default to a correct value, but
is just as likely incorrect.
As for a flag to do this, it's a bit tricky! It's actually the
Target::ReadUnsignedIntegerFromMemory() call, which takes an Address object,
which ends up mutating the address while constructing the load address. We
could pipe a flag for ReadUnsignedIntegerFromMemory down a few layers to where
that's happening, or add a flag to the Address object which indicates that it
should not be mutated down the line. Target::ReadMemory needs to take an
Address object to fall back to using the backing file if possible (important if
the corefile doesn't include the binary contents), another alternative is to
switch to Process::ReadMemory whcih takes an `addr_t` but won't fall back to
the on-disk file.
================
Comment at:
lldb/source/Plugins/DynamicLoader/Darwin-Kernel/DynamicLoaderDarwinKernel.cpp:1114
+ } else {
+ if (old_bits_value != 0)
+ m_process->SetVirtualAddressableBits(old_bits_value);
----------------
JDevlieghere wrote:
> Is this actually necessary? Does that mean that you can't do
> `process->SetVirtualAddressableBits(process->GetVirtualAddressableBits())` in
> general?
I didn't debug it through the layers, but setting the value to 0 to when the
getter returns 0, did break this.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D147462/new/
https://reviews.llvm.org/D147462
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