Re: [PATCH] selftests: clone3: Use the capget and capset syscall directly

[Shuah Khan]

On 10/11/24 00:59, zhouyuhang wrote:
> On 2024/10/10 23:50, Shuah Khan wrote:
> > On 10/10/24 06:16, zhouyuhang wrote:
> > > From: zhouyuhang <zhouyuhang@xxxxxxxxxx>
> > >
> > > The libcap commit aca076443591 ("Make cap_t operations thread safe.") added a
> > > __u8 mutex at the beginning of the struct _cap_struct,it changes the offset of
> > > the members in the structure that breaks the assumption made in the "struct libcap"
> > > definition in clone3_cap_checkpoint_restore.c.So use the capget and capset syscall
> > > directly and remove the libcap library dependency like the commit 663af70aabb7
> > > ("bpf: selftests: Add helpers to directly use the capget and capset syscall") does.
> >
> > NIT: grammar and comma spacing. Please fix those for readability.
> > e.g: Change "struct _cap_struct,it" to "struct _cap_struct, it"
> > Fix others as well.
>
> Thanks, I'll fix it in V2
>
>
> > > Signed-off-by: zhouyuhang <zhouyuhang@xxxxxxxxxx>
> > > ---
> > >   tools/testing/selftests/clone3/Makefile       |  1 -
> > >   .../clone3/clone3_cap_checkpoint_restore.c    | 60 +++++++++----------
> > >   2 files changed, 28 insertions(+), 33 deletions(-)
> > >
> > > diff --git a/tools/testing/selftests/clone3/Makefile b/tools/testing/selftests/clone3/Makefile
> > > index 84832c369a2e..59d26e8da8d2 100644
> > > --- a/tools/testing/selftests/clone3/Makefile
> > > +++ b/tools/testing/selftests/clone3/Makefile
> > > @@ -1,6 +1,5 @@
> > >   # SPDX-License-Identifier: GPL-2.0
> > >   CFLAGS += -g -std=gnu99 $(KHDR_INCLUDES)
> > > -LDLIBS += -lcap
> > >     TEST_GEN_PROGS := clone3 clone3_clear_sighand clone3_set_tid \
> > >       clone3_cap_checkpoint_restore
> > > diff --git a/tools/testing/selftests/clone3/clone3_cap_checkpoint_restore.c b/tools/testing/selftests/clone3/clone3_cap_checkpoint_restore.c
> > > index 3c196fa86c99..111912e2aead 100644
> > > --- a/tools/testing/selftests/clone3/clone3_cap_checkpoint_restore.c
> > > +++ b/tools/testing/selftests/clone3/clone3_cap_checkpoint_restore.c
> > > @@ -15,7 +15,7 @@
> > >   #include <stdio.h>
> > >   #include <stdlib.h>
> > >   #include <stdbool.h>
> > > -#include <sys/capability.h>
> > > +#include <linux/capability.h>
> > >   #include <sys/prctl.h>
> > >   #include <sys/syscall.h>
> > >   #include <sys/types.h>
> > > @@ -27,6 +27,13 @@
> > >   #include "../kselftest_harness.h"
> > >   #include "clone3_selftests.h"
> > >   +#ifndef CAP_CHECKPOINT_RESTORE
> > > +#define CAP_CHECKPOINT_RESTORE 40
> > > +#endif
> > > +
> >
> > Why is this necessary? This is defined in linux/capability.h.
> >
> > > +int capget(cap_user_header_t header, cap_user_data_t data);
> > > +int capset(cap_user_header_t header, const cap_user_data_t data);
> >
> > In general prototypes such as these should be defined in header
> > file. Why are we defining these here?
> >
> > These are defined in sys/capability.h
> >
> > I don't understand this change. You are removing sys/capability.h
> > which requires you to add these defines here. This doesn't
> > sound like a correct solution to me.
>
> I tested it on my machine without libcap-dev installed, the /usr/include/linux/capability.h
>
> is on this machine by default. Successfully compiled using #include <linux/capability.h>
>
> but not with #include <sys/capability.h>. This patch removes libcap library dependencies.
>
> And we don't use any part of sys/capability.h other than these two syscalls. So I think that's why it's necessary.

You are changing the code to not include sys/capability.h
What happens if sys/capability.h along with linux/capability.h

Do you see problems?

thanks,
-- Shuah