Hi all, The /proc/kcore interface uses vread() to read memory addresses which are in the vmalloc region, and it seems that vread() doesn't support vmap_areas which are associated with a vmap_block. As far as I can tell, those have vmap_area.vm == NULL, and get skipped during vread()'s iteration. So the end result is that the read simply returns 0's. This impacts live debuggers like gdb and drgn, which is how I stumbled upon it[1]. It looks like crash avoids the issue by doing a page table walk and reading the physical address. I'm wondering if there's any rationale for this omission from vread(): is it a simple oversight, or was it omitted due to the difficulty? Is it possible for /proc/kcore to simply take the page faults when it reads unmapped memory and handle them? (I'm sure that's already discussed or is obviously infeasible for some reason beyond me.) Ideally, I'm just looking for a way forward that allows the debugger to *work* as expected, meaning either that /proc/kcore always reads the correct data, or that the debugger can know ahead of time that it will need to do some processing (like a page table walk) first. Thanks, Stephen [1]: https://github.com/osandov/drgn/issues/217
