Re: [Xen-devel] [PATCH for-4.7 3/4] tools/xsplice: fix mixing system errno values with Xen ones.

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Fri, Apr 29, 2016 at 04:21:19PM +0200, Roger Pau Monne wrote:
> Avoid using system errno values when comparing with Xen errno values.
> 
> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> ---
> Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> Cc: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
> Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
> Cc: Wei Liu <wei.liu2@xxxxxxxxxx>
> ---
> Using errno values inside of hypercall structs is not right IMHO, but there
> are already several occurrences of this. Although I'm adding the correct XEN_
> prefixes here, it's very likely that new additions/modifications to this
> file will not take this into account, breaking it for OSes != Linux.

This seems to be a rather thorny issue.

I have a gut feeling that returning XEN_ errno to userspace program is
layering violation. They should always be translated to OS level errno
by privcmd driver.

Aren't FreeBSD and NetBSD already doing that?

Wei.

> ---
>  tools/misc/xen-xsplice.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/misc/xen-xsplice.c b/tools/misc/xen-xsplice.c
> index 695be7f..b31115c 100644
> --- a/tools/misc/xen-xsplice.c
> +++ b/tools/misc/xen-xsplice.c
> @@ -13,6 +13,8 @@
>  #include <xenctrl.h>
>  #include <xenstore.h>
>  
> +#include <xen/errno.h>
> +
>  static xc_interface *xch;
>  
>  void show_help(void)
> @@ -233,7 +235,7 @@ struct {
>          .function = xc_xsplice_revert,
>      },
>      {   .allow = XSPLICE_STATE_CHECKED,
> -        .expected = -ENOENT,
> +        .expected = -XEN_ENOENT,
>          .name = "unload",
>          .function = xc_xsplice_unload,
>      },
> @@ -276,7 +278,7 @@ int action_func(int argc, char *argv[], unsigned int idx)
>                  name, errno, strerror(errno));
>          return -1;
>      }
> -    if ( status.rc == -EAGAIN )
> +    if ( status.rc == -XEN_EAGAIN )
>      {
>          fprintf(stderr, "%s failed. Operation already in progress\n", name);
>          return -1;
> @@ -319,7 +321,7 @@ int action_func(int argc, char *argv[], unsigned int idx)
>  
>          if ( status.state != original_state )
>              break;
> -        if ( status.rc && status.rc != -EAGAIN )
> +        if ( status.rc && status.rc != -XEN_EAGAIN )
>          {
>              rc = status.rc;
>              break;
> -- 
> 2.6.4 (Apple Git-63)
> 

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