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Re: [libvirt] [PATCH] virprocess: Extend list of platforms for setns wrapper



On Mon, Sep 15, 2014 at 05:20:46PM +0200, Michal Privoznik wrote:
> On 15.09.2014 17:15, Martin Kletzander wrote:
> >On Mon, Sep 15, 2014 at 03:43:55PM +0200, Michal Privoznik wrote:
> >>Currently, the setns() wrapper is supported only for x86_64 and i686
> >>which leaves us failing to build on other platforms like arm, aarch64
> >>and so on. This means, that the wrapper needs to be extended to those
> >>platforms and make to fail on runtime not compile time.
> >>
> >>The syscall numbers for other platforms was fetched using this
> >>command:
> >>
> >>kernel.git $ git grep "define.*__NR_setns" | grep -e arm -e powerpc -e
> >>s390
> >>arch/arm/include/uapi/asm/unistd.h:#define
> >>__NR_setns                   (__NR_SYSCALL_BASE+375)
> >>arch/arm64/include/asm/unistd32.h:#define __NR_setns 375
> >>arch/powerpc/include/uapi/asm/unistd.h:#define
> >>__NR_setns               350
> >>arch/s390/include/uapi/asm/unistd.h:#define __NR_setns          339
> >>
> >>Signed-off-by: Michal Privoznik <mprivozn redhat com>
> >>---
> >>src/util/virprocess.c | 18 ++++++++++++------
> >>1 file changed, 12 insertions(+), 6 deletions(-)
> >>
> >
> >NACK, we shouldn't be duplicating syscall definitions.  There should
> >be AC_CHECK_FUNCS([setns]) (instead of AC_CHECK_FUNCS_ONCE() for the
> >syscall) and having with_lxc = "yes" and ac_cv_func_setns != "yes"
> >should result in an error.
> 
> The only problem with this might be that on systems with older glibc (and
> there is plenty of them) libvirt will fail to build / miss this feature. And
> it's not that the kernel doesn't support the namesapces. But let me see if I
> can get some ACKs on that approach you're suggesting.

That's basically what the code did before we added the #define or NR_setns.
We took the patch specifically to help Debian where the kernel has it but
glibc is outdated.

Regards,
Daniel
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