On Thu, Jan 04, 2024, bugzilla-daemon@xxxxxxxxxx wrote: > https://bugzilla.kernel.org/show_bug.cgi?id=218339 > > Bug ID: 218339 > Summary: kernel goes unresponsive if single-stepping over an > instruction which writes to an address for which a > hardware read/write watchpoint has been set > Product: Virtualization > Version: unspecified > Hardware: All > OS: Linux > Status: NEW > Severity: normal > Priority: P3 > Component: kvm > Assignee: virtualization_kvm@xxxxxxxxxxxxxxxxxxxx > Reporter: anthony.louis.eden@xxxxxxxxx > Regression: No > > In a debian QEMU/KVM virtual machine, run `gdb` on any executable (e.g. > `/usr/bin/ls`). Run the program by typing `starti`. Proceed to `_dl_start` > (i.e. `break _dl_start`, `continue`). When you get there disassemble the > function (i.e. `disas`). Find an instruction that's going to be executed for > which you can compute the address in memory it will write to. Run the program > to that instruction (i.e. `break *0xINSN`, `continue`). When you're on that > instruction, set a read/write watchpoint on the address it will write to, then > single-step (i.e. `stepi`) and the kernel will go unresponsive. By "the kernel", I assume you mean the guest kernel? > >(gdb) x/1i $pc > >=> 0x7ffff7fe6510 <_dl_start+48>: mov %rdi,-0x88(%rbp) > >(gdb) x/1wx $rbp-0x88 > >0x7fffffffec28: 0x00000000 > >(gdb) awatch *0x7fffffffec28 > >Hardware access (read/write) watchpoint 2: *0x7fffffffec28 > >(gdb) stepi > > > Looking with `journalctl`, I cannot find anything printed to dmesg. > > The kernel of the guest inside the virtual machine is Debian 6.1.0-15-amd64. > The kernel of the host running qemu-system-x86_64 is Archlinux 6.6.7-arch1-1. > gdb is version 13.1. Is this a regression or something that has always been broken? I.e. did this work on previous host kernels?
