On 18.01.2017 09:02, Ziyue Yang wrote:
> From: Ziyue Yang <yzyliv...@hotmail.com>
>
> This patch is to fix the segmentation fault caused by attaching
> GDB to a QEMU instance initialized with "-M none" option.
>
> The bug can be reproduced by
>
>> ./qemu-system-x86_64 -M none -nographic -S -s
>
> and attach a GDB to it by
>
>> gdb -ex 'target remote :1234
>
> The segmentation fault was originally caused by trying to read
> the information about CPU when communicating with GDB. However,
> it's impossible for any control flow to exist on an empty machine,
> nor can CPU's be hot plugged to an empty machine later by QOM
> commands. So I think simply disabling GDB connections on empty
> machines makes sense.
>
> Signed-off-by: Ziyue Yang <skiver.cloud....@gmail.com>
> ---
> gdbstub.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/gdbstub.c b/gdbstub.c
> index de62d26..426d55e 100644
> --- a/gdbstub.c
> +++ b/gdbstub.c
> @@ -18,6 +18,7 @@
> */
> #include "qemu/osdep.h"
> #include "qapi/error.h"
> +#include "qemu/error-report.h"
> #include "qemu/cutils.h"
> #include "cpu.h"
> #ifdef CONFIG_USER_ONLY
> @@ -1731,6 +1732,12 @@ int gdbserver_start(const char *device)
> CharDriverState *mon_chr;
> ChardevCommon common = { 0 };
>
> + if (!first_cpu) {
> + error_report("gdbstub: meaningless to attach gdb to a "
> + "machine without any CPU.");
> + return -1;
> + }
> +
> if (!device)
> return -1;
> if (strcmp(device, "none") != 0) {
> --
> 2.7.4
Reviewed-by: Thomas Huth <th...@redhat.com>
