Re: [Xen-devel] [PATCH] libxl: fix build on rather old systems

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Fri, Jan 11, 2019 at 03:09:35AM -0700, Jan Beulich wrote:
> CLONE_NEWIPC has been introduced in Linux 2.6.19 only (and into glibc
> at around that time as well). Cope with it being undefined as well as
> with the underlying kernel not knowing of it.
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> ---
> Considering how old "old" here really means, I could understand if
> this was rejected, in which case I'd carry a simplified version locally.
> I don't run such old kernels together with modern Xen, but I do
> occasionally build on such old systems.
> 
> --- a/tools/libxl/libxl_linux.c
> +++ b/tools/libxl/libxl_linux.c
> @@ -334,12 +334,24 @@ int libxl__local_dm_preexec_restrict(lib
>      unsigned i;
>  
>      /* Unshare mount and IPC namespaces.  These are unused by QEMU. */
> -    r = unshare(CLONE_NEWNS | CLONE_NEWIPC);
> +    r = unshare(CLONE_NEWNS);
>      if (r) {
> -        LOGE(ERROR, "libxl: Mount and IPC namespace unfailed");
> +        LOGE(ERROR, "libxl: Mount namespace unshare failed");
>          return ERROR_FAIL;
>      }
>  
> +#ifndef CLONE_NEWIPC /* Available as of Linux 2.6.19 / glibc 2.8 */
> +# define CLONE_NEWIPC 0x08000000

I have no problem making it build with this.

> +#endif
> +    r = unshare(CLONE_NEWIPC);
> +    if (r) {
> +        if (r && errno != EINVAL) {
> +            LOGE(ERROR, "libxl: IPC namespace unshare failed");
> +            return ERROR_FAIL;
> +        }
> +        LOG(WARN, "libxl: IPC namespace unshare unavailable");

But I guess whether it should be allowed to continue or not is another
question. Do we consider this IPC namespace "must-have"?

CC George as well.

Wei.

> +    }
> +
>      /* Set various "easy" rlimits */
>      for (i = 0; rlimits[i].resource != RLIMIT_NLIMITS; i++) {
>          struct rlimit rlim;
> 
> 
> 
> 

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