Re: [Qemu-devel] [PATCH] gdbstub: Support AUXV packet for debugging PIE executables.

[Paolo Bonzini <pbonzini@redhat.com>]

CCing Riku Voipio for a review.

Paolo

On 23/11/2014 14:28, Wei-cheng, Wang wrote:
> Hi,
> 
> This patch adds support for sending AUXV packet.
> This is required for debugging Linux position independent executables.
> Otherwise, gdb client cannot find out where the executable is loaded.
> 
> Signed-off-by: Wei-cheng, Wang <cole945@gmail.com>
> ---
>  gdbstub.c | 41 +++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 41 insertions(+)
> 
> diff --git a/gdbstub.c b/gdbstub.c
> index d1b5afd..30f3bbc 100644
> --- a/gdbstub.c
> +++ b/gdbstub.c
> @@ -1127,6 +1127,7 @@ static int gdb_handle_packet(GDBState *s, const
> char *line_buf)
>              if (cc->gdb_core_xml_file != NULL) {
>                  pstrcat(buf, sizeof(buf), ";qXfer:features:read+");
>              }
> +            pstrcat(buf, sizeof(buf), ";qXfer:auxv:read+");
>              put_packet(s, buf);
>              break;
>          }
> @@ -1173,6 +1174,46 @@ static int gdb_handle_packet(GDBState *s, const
> char *line_buf)
>              put_packet_binary(s, buf, len + 1);
>              break;
>          }
> +#ifdef CONFIG_USER_ONLY
> +        if (strncmp(p, "Xfer:auxv:read:", 15) == 0) {
> +            TaskState *ts = s->c_cpu->opaque;
> +            target_ulong auxv = ts->info->saved_auxv;
> +            target_ulong auxv_len = ts->info->auxv_len;
> +            char *ptr;
> +
> +            p += 15;
> +            while (*p && *p != ':')
> +                p++;
> +            p++;
> +
> +            addr = strtoul(p, (char **)&p, 16);
> +            if (*p == ',')
> +                p++;
> +            len = strtoul(p, (char **)&p, 16);
> +
> +            ptr = lock_user(VERIFY_READ, auxv, auxv_len, 0);
> +            if (ptr == NULL) {
> +                break;
> +            }
> +
> +            if (addr > len) {
> +                snprintf(buf, sizeof(buf), "E00");
> +                put_packet(s, buf);
> +                break;
> +            }
> +            if (len > (MAX_PACKET_LENGTH - 5) / 2)
> +                len = (MAX_PACKET_LENGTH - 5) / 2;
> +            if (len < auxv_len - addr) {
> +                buf[0] = 'm';
> +                len = memtox(buf + 1, ptr + addr, len);
> +            } else {
> +                buf[0] = 'l';
> +                len = memtox(buf + 1, ptr + addr, auxv_len - addr);
> +            }
> +            put_packet_binary(s, buf, len + 1);
> +            unlock_user(ptr, auxv, len);
> +        }
> +#endif /* !CONFIG_USER_ONLY */
>          /* Unrecognised 'q' command.  */
>          goto unknown_command;
>