Re: [Qemu-devel] [PATCH v1 2/2] gdbstub: don't fail on vCont; C04:0; c packets

[Claudio Imbrenda <imbrenda@linux.vnet.ibm.com>]

On Wed, 31 May 2017 16:09:33 +0100
Alex Bennée <alex.bennee@linaro.org> wrote:

> The thread-id of 0 means any CPU but we then ignore the fact we find
> the first_cpu in this case who can have an index of 0. Instead of
> bailing out just test if we have managed to match up thread-id to a
> CPU.
> 
> Otherwise you get:
>   gdb_handle_packet: command='vCont;C04:0;c'
>   put_packet: reply='E22'
> 
> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
> ---
>  gdbstub.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/gdbstub.c b/gdbstub.c
> index a249846954..29c9ed3002 100644
> --- a/gdbstub.c
> +++ b/gdbstub.c
> @@ -934,8 +934,8 @@ static int gdb_handle_vcont(GDBState *s, const
> char *p)
>               * CPU first, and only then we can use its index.
>               */
>              cpu = find_cpu(idx);
> -            /* invalid CPU/thread specified */
> -            if (!idx || !cpu) {
> +            /* invalid thread specified, cpu not found. */
> +            if (!cpu) {
>                  res = -EINVAL;
>                  goto out;
>              }

This is strange. cpu_index() is defined as:

static inline int cpu_index(CPUState *cpu)
{
#if defined(CONFIG_USER_ONLY)
    return cpu->host_tid;
#else
    return cpu->cpu_index + 1;
#endif
}

therefore it shouldn't return 0 under any circumstance, and
find_cpu(idx) should also fail if idx == 0, because internally it also
uses cpu_index()

on the other hand, you say that the patch does fix the problem for you,
which really confuses me.



(probably) completely unrelatedly, this:

res = qemu_strtoul(p + 1, &p, 16, &tmp);

should be like this instead:

res = qemu_strtoul(p, &p, 16, &tmp);

but this shouldn't impact you in any way.