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



On Mon, Sep 15, 2014 at 04:22:18PM +0100, Daniel P. Berrange wrote:
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glibc is outdated.


Either Debian should patch their glibc or we should at lease use
SYS_setns IMHO.

Regards,
Daniel
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