I'm adding LLDB support for an unconventional platform which uses two stacks: one purely for return addresses and another for frame context (spilled registers, local variables, etc). There is no explicit link between the two stacks, i.e. the frame context doesn't include any pointer or index to identify the return address: the epilog for a subroutine amounts to unwinding the frame context then finally popping the top return address from the return stack. It has some resemblance to the Intel CET scheme of shadow stacks, but without the primary stack having a copy of the return address.
I can extend the emulation of the platform to better support LLDB. For example while the real hardware platform provides no access to the return address stack the emulation can expose it in the memory map, provide an additional debug register for querying it, etc, which DWARF expressions could then extract return addresses from. However doing this seems to require knowing the frame number and I haven't found a way of doing this (a pseudo-register manipulated by DWARF expressions worked but needed some LLDB hacks to sneak it through the existing link register handling, also seemed likely to be unstable against LLDB implementation changes) Is there a way to access the call frame number (or a reliable proxy) from a DWARF expression? Or an existing example of unwinding a shadow stack? Thanks, Tom _______________________________________________ lldb-dev mailing list lldb-dev@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-dev
