[igt-dev] [PATCH i-g-t v3] ts/core_setmaster: new test for drop/set master semantics

[Emil Velikov]

On Tue, 3 Mar 2020 at 13:13, Petri Latvala <petri.latvala at intel.com> wrote:
>
> On Mon, Mar 02, 2020 at 05:33:14PM +0000, Emil Velikov wrote:
> > From: Emil Velikov <emil.velikov at collabora.com>
> >
> > This test adds three distinct subtests:
> >  - drop/set master as root
> >  - drop/set master as non-root
> >  - drop/set master for a shared fd
> >
> > Currently the second subtest will fail, with kernel patch to address
> > that has been submitted.
> >
> > v2: Add to the autotools build
> > v3:
> >  - Add igt_describe()
> >  - Use igt_fixture() for tweak_perm
> >  - Enhance comments
> >
> > Cc: Petri Latvala <petri.latvala at intel.com>
> > Signed-off-by: Emil Velikov <emil.velikov at collabora.com>
> > ---
> >  tests/Makefile.sources |   1 +
> >  tests/core_setmaster.c | 206 +++++++++++++++++++++++++++++++++++++++++
> >  tests/meson.build      |   1 +
> >  3 files changed, 208 insertions(+)
> >  create mode 100644 tests/core_setmaster.c
> >
> > diff --git a/tests/Makefile.sources b/tests/Makefile.sources
> > index b87d6333..5da36a91 100644
> > --- a/tests/Makefile.sources
> > +++ b/tests/Makefile.sources
> > @@ -18,6 +18,7 @@ TESTS_progs = \
> >       core_getclient \
> >       core_getstats \
> >       core_getversion \
> > +     core_setmaster \
> >       core_setmaster_vs_auth \
> >       debugfs_test \
> >       dmabuf \
> > diff --git a/tests/core_setmaster.c b/tests/core_setmaster.c
> > new file mode 100644
> > index 00000000..58ed9771
> > --- /dev/null
> > +++ b/tests/core_setmaster.c
> > @@ -0,0 +1,206 @@
> > +/*
> > + * Copyright © 2020 Collabora, Ltd.
> > + *
> > + * Permission is hereby granted, free of charge, to any person obtaining a
> > + * copy of this software and associated documentation files (the "Software"),
> > + * to deal in the Software without restriction, including without limitation
> > + * the rights to use, copy, modify, merge, publish, distribute, sublicense,
> > + * and/or sell copies of the Software, and to permit persons to whom the
> > + * Software is furnished to do so, subject to the following conditions:
> > + *
> > + * The above copyright notice and this permission notice (including the next
> > + * paragraph) shall be included in all copies or substantial portions of the
> > + * Software.
> > + *
> > + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> > + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> > + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
> > + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
> > + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
> > + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
> > + * IN THE SOFTWARE.
> > + *
> > + * Authors:
> > + *    Emil Velikov <emil.l.velikov at gmail.com>
> > + *
> > + */
> > +
> > +/*
> > + * Testcase: Check that drop/setMaster behaves correctly wrt root/user access
> > + *
> > + * Test checks if the ioctls succeed or fail, depending if the applications was
> > + * run with root, user privileges or if we have separate privileged arbitrator.
> > + */
> > +
> > +#include "igt.h"
> > +#include <unistd.h>
> > +#include <stdlib.h>
> > +#include <stdio.h>
> > +#include <string.h>
> > +#include <sys/stat.h>
> > +
> > +IGT_TEST_DESCRIPTION("Check that Drop/SetMaster behaves correctly wrt root/user"
> > +                  " access");
> > +
> > +static bool is_master(int fd)
> > +{
> > +     /* FIXME: replace with drmIsMaster once we bumped libdrm version */
> > +     return drmAuthMagic(fd, 0) != -EACCES;
> > +}
> > +
> > +static void check_drop_set(void)
> > +{
> > +     int master;
> > +
> > +     master = __drm_open_driver(DRIVER_ANY);
> > +
> > +     /* Ensure we have a valid device. This is _extremely_ unlikely to
> > +      * trigger as tweak_perm() aims to ensure we have the correct rights.
> > +      * Although:
> > +      * - according to the manual igt_drop_root() + igt_skip() is broken
>
> I asked for clarification on this and didn't get a reply. I'm not
> seeing such a mention. Well, there is the text warning about
> igt_drop_root() and atexit handlers and recommending the use of
> igt_drop_root() in a child process to avoid issues, and this is in a
> child process.
>
> Whatever I'm missing here surely also applies to igt_assert as well?
>
Darn it ... got the wrong function which explains the confusion.

In particular igt_skip() isn't propagated properly within a
igt_fork(), as documented [1].
This results in a) the test failing [2] (instead of skipping) with b)
semi-magical trace.

If the IGT team is happy with those pitfalls, I can switch to igt_require :-)

[1] https://gitlab.freedesktop.org/drm/igt-gpu-tools/-/blob/master/lib/igt_core.h#L1045
[2] igt_skip: Assertion `"!test_child` failed


>
> > +      * - there is _no_ guarantee that we'll open a device handled by
> > +      * tweak_perm()
>
> This is a point that came to mind later, the building blocks for that
> guarantee are in igt_device_scan.
>
> 1) If filter already set (test being run with --device), use that
>    filter (igt_device_filter_get or so). Otherwise loop through the
>    generated card%u names, using drm:/dev/dri/card%u as the
>    filter. igt_device_scan.c stuff already has a list of all possible
>    devices but I don't see an easy way to get to the list.
>
> 2) igt_device_card_match() gets you a card
>
> 3) card->card should be the path to /dev/dri to chmod on
>
> 4) igt_open_card(card) gives you an fd to that card
>
Not entirely sure what you're suggesting here. Can you please elaborate?

>
> > +      * - having a device is integral part of the test
>
> It's an integral part of all tests. The issue with the use of
> igt_require vs igt_assert is whether it's a prerequisite or the thing
> you're actually testing.
>
The latter. I can reword that comment to "successfully opening a
device is part of the test" or anything that you'd prefer.

>
> > +      */
> > +     igt_assert_neq(master, -1);
> > +
> > +     /* At this point we're master capable due to:
> > +      * - being root - always
> > +      * - normal user - as the only drm only drm client (on this VT)
> > +      */
> > +     igt_assert_eq(is_master(master), true);
>
> Just igt_assert(is_master(master))
>
Sure fixed, alongside the s/ts/test/ type in the summary.

Is there some dos and don'ts about which igt_assert* functions to use?
Would it make sense to write short list + mass conversion to the
recommended ones?

Thanks
Emil