netdev - Re: [PATCH v2 bpf-next 7/7] selftests/bpf: test kernel module ksym externs

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Date:   Mon, 11 Jan 2021 13:40:46 -0800
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Yonghong Song <yhs@...com>
Cc:     Andrii Nakryiko <andrii@...nel.org>, bpf <bpf@...r.kernel.org>,
        Networking <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Kernel Team <kernel-team@...com>, Hao Luo <haoluo@...gle.com>
Subject: Re: [PATCH v2 bpf-next 7/7] selftests/bpf: test kernel module ksym externs

On Sun, Jan 10, 2021 at 8:18 PM Yonghong Song <yhs@...com> wrote:
>
>
>
> On 1/8/21 2:09 PM, Andrii Nakryiko wrote:
> > Add per-CPU variable to bpf_testmod.ko and use those from new selftest to
> > validate it works end-to-end.
> >
> > Signed-off-by: Andrii Nakryiko <andrii@...nel.org>
>
> Ack with a nit below.
>
> Acked-by: Yonghong Song <yhs@...com>
>
> > ---
> >   .../selftests/bpf/bpf_testmod/bpf_testmod.c   |  3 ++
> >   .../selftests/bpf/prog_tests/ksyms_module.c   | 33 +++++++++++++++++++
> >   .../selftests/bpf/progs/test_ksyms_module.c   | 26 +++++++++++++++
> >   3 files changed, 62 insertions(+)
> >   create mode 100644 tools/testing/selftests/bpf/prog_tests/ksyms_module.c
> >   create mode 100644 tools/testing/selftests/bpf/progs/test_ksyms_module.c
> >
> > diff --git a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
> > index 2df19d73ca49..0b991e115d1f 100644
> > --- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
> > +++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
> > @@ -3,6 +3,7 @@
> >   #include <linux/error-injection.h>
> >   #include <linux/init.h>
> >   #include <linux/module.h>
> > +#include <linux/percpu-defs.h>
> >   #include <linux/sysfs.h>
> >   #include <linux/tracepoint.h>
> >   #include "bpf_testmod.h"
> > @@ -10,6 +11,8 @@
> >   #define CREATE_TRACE_POINTS
> >   #include "bpf_testmod-events.h"
> >
> > +DEFINE_PER_CPU(int, bpf_testmod_ksym_percpu) = 123;
> > +
> >   noinline ssize_t
> >   bpf_testmod_test_read(struct file *file, struct kobject *kobj,
> >                     struct bin_attribute *bin_attr,
> > diff --git a/tools/testing/selftests/bpf/prog_tests/ksyms_module.c b/tools/testing/selftests/bpf/prog_tests/ksyms_module.c
> > new file mode 100644
> > index 000000000000..7fa3d8b6ca30
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/prog_tests/ksyms_module.c
> > @@ -0,0 +1,33 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/* Copyright (c) 2021 Facebook */
> > +
> > +#include <test_progs.h>
> > +#include <bpf/libbpf.h>
> > +#include <bpf/btf.h>
> > +#include "test_ksyms_module.skel.h"
> > +
> > +static int duration;
> > +
> > +void test_ksyms_module(void)
> > +{
> > +     struct test_ksyms_module* skel;
> > +     struct test_ksyms_module__bss *bss;
> > +     int err;
> > +
> > +     skel = test_ksyms_module__open_and_load();
> > +     if (CHECK(!skel, "skel_open", "failed to open skeleton\n"))
> > +             return;
> > +     bss = skel->bss;
> > +
> > +     err = test_ksyms_module__attach(skel);
> > +     if (CHECK(err, "skel_attach", "skeleton attach failed: %d\n", err))
> > +             goto cleanup;
> > +
> > +     usleep(1);
>
> The above bss = skel->bss might be moved here for better readability.
> Or better, you can remove definition bss and just use skel->bss
> in below two ASSERT_EQs.

Sure, I'll just inline for such a short test.

>
> > +     ASSERT_EQ(bss->triggered, true, "triggered");
> > +     ASSERT_EQ(bss->out_mod_ksym_global, 123, "global_ksym_val");
> > +
> > +cleanup:
> > +     test_ksyms_module__destroy(skel);
> > +}
> > diff --git a/tools/testing/selftests/bpf/progs/test_ksyms_module.c b/tools/testing/selftests/bpf/progs/test_ksyms_module.c
> > new file mode 100644
> > index 000000000000..d6a0b3086b90
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/progs/test_ksyms_module.c
> > @@ -0,0 +1,26 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/* Copyright (c) 2021 Facebook */
> > +
> > +#include "vmlinux.h"
> > +
> > +#include <bpf/bpf_helpers.h>
> > +
> > +extern const int bpf_testmod_ksym_percpu __ksym;
> > +
> > +int out_mod_ksym_global = 0;
> > +bool triggered = false;
> > +
> > +SEC("raw_tp/sys_enter")
> > +int handler(const void *ctx)
> > +{
> > +     int *val;
> > +     __u32 cpu;
> > +
> > +     val = (int *)bpf_this_cpu_ptr(&bpf_testmod_ksym_percpu);
> > +     out_mod_ksym_global = *val;
> > +     triggered = true;
> > +
> > +     return 0;
> > +}
> > +
> > +char LICENSE[] SEC("license") = "GPL";
> >