[Pdbg] [PATCH v2 36/39] gdbserver: send regs with stop reason

[Joel Stanley]

On Wed, 20 Apr 2022 at 06:51, Nicholas Piggin <npiggin at gmail.com> wrote:
>
> The gdb protocol allows sending register values of the stopped thread
> with the stop-reason packet. This reduces round-trips because the client
> doesn't have to get registers after stopping. This is a significant win
> because getting registers requires multiple commands so it saves about
> 10 commands (round-trips).
>
> Signed-off-by: Nicholas Piggin <npiggin at gmail.com>
> ---
>  src/pdbgproxy.c | 37 +++++++++++++++++++++++++++++++++++++
>  1 file changed, 37 insertions(+)
>
> diff --git a/src/pdbgproxy.c b/src/pdbgproxy.c
> index 6b9bdf90..d50121c0 100644
> --- a/src/pdbgproxy.c
> +++ b/src/pdbgproxy.c
> @@ -202,7 +202,11 @@ static void send_stop_for_thread(struct pdbg_target *target)
>         uint64_t pir = gdb_thread->pir;
>         char data[MAX_RESP_LEN];
>         size_t s = 0;
> +       struct thread_regs regs;
> +       uint64_t value;
> +       uint32_t value32;
>         int sig;
> +       int i;
>
>         if (gdb_thread->stop_attn)
>                 sig = 5; /* TRAP */
> @@ -213,6 +217,39 @@ static void send_stop_for_thread(struct pdbg_target *target)
>
>         s += snprintf(data + s, sizeof(data) - s, "T%02uthread:%04" PRIx64 ";%s", sig, pir, sig == 5 ? "swbreak:;" : "");

Ignore my comment about s in the earlier patch.

Reviewed-by: Joel Stanley <joel at jms.id.au>

>
> +       if (thread_getregs(target, &regs))
> +               PR_ERROR("Error reading gprs\n");

Forge ahead anyway? Makes sense I guess. Should we zero out 'regs' first?

> +
> +       for (i = 0; i < 32; i++)
> +               s += snprintf(data + s, sizeof(data) - s, "%x:%016" PRIx64 ";", i, be64toh(regs.gprs[i]));
> +
> +       thread_getnia(target, &value);
> +       s += snprintf(data + s, sizeof(data) - s, "%x:%016" PRIx64 ";", 0x40, be64toh(value));
> +
> +       thread_getmsr(target, &value);
> +       s += snprintf(data + s, sizeof(data) - s, "%x:%016" PRIx64 ";", 0x41, be64toh(value));
> +
> +       thread_getcr(target, &value32);
> +       s += snprintf(data + s, sizeof(data) - s, "%x:%08" PRIx32 ";", 0x42, be32toh(value32));
> +
> +       thread_getspr(target, SPR_LR, &value);
> +       s += snprintf(data + s, sizeof(data) - s, "%x:%016" PRIx64 ";", 0x43, be64toh(value));
> +
> +       thread_getspr(target, SPR_CTR, &value);
> +       s += snprintf(data + s, sizeof(data) - s, "%x:%016" PRIx64 ";", 0x44, be64toh(value));
> +
> +       thread_getspr(target, SPR_XER, &value);
> +       s += snprintf(data + s, sizeof(data) - s, "%x:%08" PRIx32 ";", 0x45, be32toh(value));
> +
> +       thread_getspr(target, SPR_FPSCR, &value);
> +       s += snprintf(data + s, sizeof(data) - s, "%x:%08" PRIx32 ";", 0x46, be32toh(value));
> +
> +       thread_getspr(target, SPR_VSCR, &value);
> +       s += snprintf(data + s, sizeof(data) - s, "%x:%08" PRIx32 ";", 0x67, be32toh(value));
> +
> +       thread_getspr(target, SPR_VRSAVE, &value);
> +       s += snprintf(data + s, sizeof(data) - s, "%x:%08" PRIx32 ";", 0x68, be32toh(value));
> +
>         send_response(fd, data);
>  }
>
> --
> 2.35.1
>
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