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    SubjectRe: [PATCH bpf-next v5 3/7] bpf: lsm: provide attachment points for BPF LSM programs
    On 23-Mär 12:59, Andrii Nakryiko wrote:
    > On Mon, Mar 23, 2020 at 9:45 AM KP Singh <kpsingh@chromium.org> wrote:
    > >
    > > From: KP Singh <kpsingh@google.com>
    > >
    > > When CONFIG_BPF_LSM is enabled, nops functions, bpf_lsm_<hook_name>, are
    > > generated for each LSM hook. These nops are initialized as LSM hooks in
    > > a subsequent patch.
    > >
    > > Signed-off-by: KP Singh <kpsingh@google.com>
    > > Reviewed-by: Brendan Jackman <jackmanb@google.com>
    > > Reviewed-by: Florent Revest <revest@google.com>
    > > ---
    > > include/linux/bpf_lsm.h | 21 +++++++++++++++++++++
    > > kernel/bpf/bpf_lsm.c | 19 +++++++++++++++++++
    > > 2 files changed, 40 insertions(+)
    > > create mode 100644 include/linux/bpf_lsm.h
    > >
    > > diff --git a/include/linux/bpf_lsm.h b/include/linux/bpf_lsm.h
    > > new file mode 100644
    > > index 000000000000..c6423a140220
    > > --- /dev/null
    > > +++ b/include/linux/bpf_lsm.h
    > > @@ -0,0 +1,21 @@
    > > +/* SPDX-License-Identifier: GPL-2.0 */
    > > +
    > > +/*
    > > + * Copyright (C) 2020 Google LLC.
    > > + */
    > > +
    > > +#ifndef _LINUX_BPF_LSM_H
    > > +#define _LINUX_BPF_LSM_H
    > > +
    > > +#include <linux/bpf.h>
    > > +#include <linux/lsm_hooks.h>
    > > +
    > > +#ifdef CONFIG_BPF_LSM
    > > +
    > > +#define LSM_HOOK(RET, NAME, ...) RET bpf_lsm_##NAME(__VA_ARGS__);
    > > +#include <linux/lsm_hook_names.h>
    > > +#undef LSM_HOOK
    > > +
    > > +#endif /* CONFIG_BPF_LSM */
    > > +
    > > +#endif /* _LINUX_BPF_LSM_H */
    > > diff --git a/kernel/bpf/bpf_lsm.c b/kernel/bpf/bpf_lsm.c
    > > index 82875039ca90..530d137f7a84 100644
    > > --- a/kernel/bpf/bpf_lsm.c
    > > +++ b/kernel/bpf/bpf_lsm.c
    > > @@ -7,6 +7,25 @@
    > > #include <linux/filter.h>
    > > #include <linux/bpf.h>
    > > #include <linux/btf.h>
    > > +#include <linux/lsm_hooks.h>
    > > +#include <linux/bpf_lsm.h>
    > > +
    > > +/* For every LSM hook that allows attachment of BPF programs, declare a NOP
    > > + * function where a BPF program can be attached as an fexit trampoline.
    > > + */
    > > +#define LSM_HOOK(RET, NAME, ...) LSM_HOOK_##RET(NAME, __VA_ARGS__)
    > > +
    > > +#define LSM_HOOK_int(NAME, ...) \
    > > +noinline __weak int bpf_lsm_##NAME(__VA_ARGS__) \
    > > +{ \
    > > + return 0; \
    > > +}
    > > +
    > > +#define LSM_HOOK_void(NAME, ...) \
    > > +noinline __weak void bpf_lsm_##NAME(__VA_ARGS__) {}
    > > +
    >
    > Could unify with:
    >
    > #define LSM_HOOK(RET, NAME, ...) noinline __weak RET bpf_lsm_##NAME(__VA_ARGS__)
    > {
    > return (RET)0;
    > }
    >
    > then you don't need LSM_HOOK_int and LSM_HOOK_void.

    Nice.

    But, given that we are adding default values and that
    they are only needed for int hooks, we will need to keep the macros
    separate for int and void. Or, Am I missing a trick here?

    - KP

    >
    > > +#include <linux/lsm_hook_names.h>
    > > +#undef LSM_HOOK
    > >
    > > const struct bpf_prog_ops lsm_prog_ops = {
    > > };
    > > --
    > > 2.20.1
    > >

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