Re: [Xen-devel] [BUGFIX][PATCH v2 5/5] xg_main: If XEN_DOMCTL_gdbsx_guestmemio fails then force error.

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2014-01-07 at 19:25 -0500, Don Slutz wrote:
> Without this gdb does not report an error.
> 
> With this patch and using a 1G hvm domU:
> 
> (gdb) x/1xh 0x6ae9168b
> 0x6ae9168b:     Cannot access memory at address 0x6ae9168b
> 
> Drop output of iop->remain because it most likely will be zero.
> This leads to a strange message:
> 
> ERROR: failed to read 0 bytes. errno:14 rc:-1
> 
> Add address to write error because it may be the only message
> displayed.
> 
> Note: currently XEN_DOMCTL_gdbsx_guestmemio does not change 'iop' on
> error and so iop->remain will be zero.
> 
> Signed-off-by: Don Slutz <dslutz@xxxxxxxxxxx>
> ---
>  tools/debugger/gdbsx/xg/xg_main.c | 13 +++++++++----
>  1 file changed, 9 insertions(+), 4 deletions(-)
> 
> diff --git a/tools/debugger/gdbsx/xg/xg_main.c 
> b/tools/debugger/gdbsx/xg/xg_main.c
> index 3b2a285..0fc3f82 100644
> --- a/tools/debugger/gdbsx/xg/xg_main.c
> +++ b/tools/debugger/gdbsx/xg/xg_main.c
> @@ -787,8 +787,10 @@ xg_read_mem(uint64_t guestva, char *tobuf, int 
> tobuf_len, uint64_t pgd3val)
>      iop->gwr = 0;       /* not writing to guest */
>  
>      if ( (rc = _domctl_hcall(XEN_DOMCTL_gdbsx_guestmemio, tobuf, tobuf_len)) 
> )
> -        XGTRC("ERROR: failed to read %d bytes. errno:%d rc:%d\n",
> -              iop->remain, errno, rc);
> +    {
> +        XGTRC("ERROR: failed to read bytes. errno:%d rc:%d\n", errno, rc);

Is it worth printing the expect number (i.e. the input) of bytes? Is
that buflen here?

> +        return tobuf_len;
> +    }
>  
>      for(i=0; i < XGMIN(8, tobuf_len); u.buf8[i]=tobuf[i], i++);
>      XGTRC("X:remain:%d buf8:0x%llx\n", iop->remain, u.llbuf8);
> @@ -818,8 +820,11 @@ xg_write_mem(uint64_t guestva, char *frombuf, int 
> buflen, uint64_t pgd3val)
>      iop->gwr = 1;       /* writing to guest */
>  
>      if ((rc=_domctl_hcall(XEN_DOMCTL_gdbsx_guestmemio, frombuf, buflen)))
> -        XGERR("ERROR: failed to write %d bytes. errno:%d rc:%d\n", 
> -              iop->remain, errno, rc);
> +    {
> +        XGERR("ERROR: failed to write bytes to %llx. errno:%d rc:%d\n",
> +              guestva, errno, rc);

Same here.

> +        return buflen;
> +    }
>      return iop->remain;
>  }
>  



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