gdb fails in arm chroot

Not linked to qemu-kvm ? Tentatively reaffecting to gdb, please revert to qemu-kvm with extra information if necessary.

From the original bug description, this is an emulated arm chroot on x86 and gdb is failing because ptrace is not implemented /in qemu/.

I don't know if this is still an issue with qemu-linaro; we should retest.

I don't think qemu supports ptrace, and it might or might not be hard to implement, Peter would be in a better position to comment

However the usual way to gdb with qemu's linux-user emulation is explained in http://lists.linaro.org/pipermail/linaro-dev/2011-January/002022.html and doesn't require qemu to implement ptrace

I think implementing ptrace in user mode qemu would be remarkably tricky. You'd have to somehow identify that the process you were trying to attach to was really another user-mode qemu process and not a native binary, and then you'd need to establish communication with it over some channel, so you could implement the ptrace syscalls by asking the other qemu to do things for you. There are undoubtedly some really nasty edge cases, like what happens if you try to attach and the other qemu is sat in a blocking syscall, making sure the "gdb forks and execs the binary to debug" case works properly, and so on.

In short, it's a lot of effort for a remarkably small gain, when you can just attach a cross-gdb to qemu directly as Loic suggests.