Re: [Qemu-devel] [PATCH] gdbstub: Implement Xfer:auxv:read

[Peter Maydell]

On 1 July 2015 at 12:00, Bhushan Attarde <address@hidden> wrote:
> Implementation of "Xfer:auxv:read" to provide auxiliary vector information
> to clients which relies on it.
>
> For example: AT_ENTRY in auxiliary vector provides the entry point 
> information.
> Client can use this information to compare it with entry point mentioned in
> executable to calculate load offset and then update the load addresses
> accordingly.
>
> Signed-off-by: Bhushan Attarde <address@hidden>
> ---
>  gdbstub.c | 47 +++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 47 insertions(+)
>
> diff --git a/gdbstub.c b/gdbstub.c
> index cea2a84..bdcaa6b 100644
> --- a/gdbstub.c
> +++ b/gdbstub.c
> @@ -1153,6 +1153,9 @@ 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+");
>              }
> +#ifdef CONFIG_USER_ONLY
> +            pstrcat(buf, sizeof(buf), ";qXfer:auxv:read+");
> +#endif
>              put_packet(s, buf);
>              break;
>          }
> @@ -1199,6 +1202,50 @@ 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);
> +            }

The bulk of this code for parsing out the arguments in a
qXfer:OBJECT:read:ANNEX:OFFSET,LENGTH packet is identical
to that we already have for handling Xfer:features:read.
We should factor this out neatly rather than duplicating it.

thanks
-- PMM