[13/14] bpf: Add dispatchers to kallsyms
diff mbox series

Message ID 20200208154209.1797988-14-jolsa@kernel.org
State Superseded
Delegated to: BPF Maintainers
Headers show
Series
  • bpf: Add trampoline and dispatcher to /proc/kallsyms
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Commit Message

Jiri Olsa Feb. 8, 2020, 3:42 p.m. UTC
Adding dispatchers to kallsyms. It's displayed as
  bpf_dispatcher_<NAME>

where NAME is the name of dispatcher.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 include/linux/bpf.h     | 19 ++++++++++++-------
 kernel/bpf/dispatcher.c |  6 ++++++
 2 files changed, 18 insertions(+), 7 deletions(-)

Comments

Andrii Nakryiko Feb. 11, 2020, 7:03 p.m. UTC | #1
On Sat, Feb 8, 2020 at 7:43 AM Jiri Olsa <jolsa@kernel.org> wrote:
>
> Adding dispatchers to kallsyms. It's displayed as
>   bpf_dispatcher_<NAME>
>
> where NAME is the name of dispatcher.
>
> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> ---
>  include/linux/bpf.h     | 19 ++++++++++++-------
>  kernel/bpf/dispatcher.c |  6 ++++++
>  2 files changed, 18 insertions(+), 7 deletions(-)
>
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index b91bac10d3ea..837cdc093d2c 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -520,6 +520,7 @@ struct bpf_dispatcher {
>         int num_progs;
>         void *image;
>         u32 image_off;
> +       struct bpf_ksym ksym;
>  };
>
>  static __always_inline unsigned int bpf_dispatcher_nop_func(
> @@ -535,13 +536,17 @@ struct bpf_trampoline *bpf_trampoline_lookup(u64 key);
>  int bpf_trampoline_link_prog(struct bpf_prog *prog);
>  int bpf_trampoline_unlink_prog(struct bpf_prog *prog);
>  void bpf_trampoline_put(struct bpf_trampoline *tr);
> -#define BPF_DISPATCHER_INIT(name) {                    \
> -       .mutex = __MUTEX_INITIALIZER(name.mutex),       \
> -       .func = &name##_func,                           \
> -       .progs = {},                                    \
> -       .num_progs = 0,                                 \
> -       .image = NULL,                                  \
> -       .image_off = 0                                  \
> +#define BPF_DISPATCHER_INIT(_name) {                           \
> +       .mutex = __MUTEX_INITIALIZER(_name.mutex),              \
> +       .func = &_name##_func,                                  \
> +       .progs = {},                                            \
> +       .num_progs = 0,                                         \
> +       .image = NULL,                                          \
> +       .image_off = 0,                                         \
> +       .ksym = {                                               \
> +               .name = #_name,                                 \
> +               .lnode = LIST_HEAD_INIT(_name.ksym.lnode),      \
> +       },                                                      \
>  }
>
>  #define DEFINE_BPF_DISPATCHER(name)                                    \
> diff --git a/kernel/bpf/dispatcher.c b/kernel/bpf/dispatcher.c
> index b3e5b214fed8..8771d2cc5840 100644
> --- a/kernel/bpf/dispatcher.c
> +++ b/kernel/bpf/dispatcher.c
> @@ -152,6 +152,12 @@ void bpf_dispatcher_change_prog(struct bpf_dispatcher *d, struct bpf_prog *from,
>         if (!changed)
>                 goto out;
>
> +       if (!prev_num_progs)
> +               bpf_image_ksym_add(d->image, &d->ksym);
> +
> +       if (!d->num_progs)
> +               bpf_ksym_del(&d->ksym);
> +
>         bpf_dispatcher_update(d, prev_num_progs);

On slightly unrelated note: seems like bpf_dispatcher_update won't
propagate any lower-level errors back, which seems pretty bad as a
bunch of stuff can go wrong.

Björn, was it a conscious decision or this just slipped through the cracks?

Jiri, reason I started looking at this was twofold:
1. you add/remove symbol before dispatcher is updated, which is
different order from BPF trampoline updates. I think updating symbols
after successful update makes more sense, no?
2. I was wondering if bpf_dispatcher_update() could return 0/1 (and <0
on error, of course), depending on whether dispatcher is present or
not. Though I'm not hard set on this.

>  out:
>         mutex_unlock(&d->mutex);
> --
> 2.24.1
>
Jiri Olsa Feb. 12, 2020, 10:52 a.m. UTC | #2
On Tue, Feb 11, 2020 at 11:03:23AM -0800, Andrii Nakryiko wrote:
> On Sat, Feb 8, 2020 at 7:43 AM Jiri Olsa <jolsa@kernel.org> wrote:
> >
> > Adding dispatchers to kallsyms. It's displayed as
> >   bpf_dispatcher_<NAME>
> >
> > where NAME is the name of dispatcher.
> >
> > Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> > ---
> >  include/linux/bpf.h     | 19 ++++++++++++-------
> >  kernel/bpf/dispatcher.c |  6 ++++++
> >  2 files changed, 18 insertions(+), 7 deletions(-)
> >
> > diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> > index b91bac10d3ea..837cdc093d2c 100644
> > --- a/include/linux/bpf.h
> > +++ b/include/linux/bpf.h
> > @@ -520,6 +520,7 @@ struct bpf_dispatcher {
> >         int num_progs;
> >         void *image;
> >         u32 image_off;
> > +       struct bpf_ksym ksym;
> >  };
> >
> >  static __always_inline unsigned int bpf_dispatcher_nop_func(
> > @@ -535,13 +536,17 @@ struct bpf_trampoline *bpf_trampoline_lookup(u64 key);
> >  int bpf_trampoline_link_prog(struct bpf_prog *prog);
> >  int bpf_trampoline_unlink_prog(struct bpf_prog *prog);
> >  void bpf_trampoline_put(struct bpf_trampoline *tr);
> > -#define BPF_DISPATCHER_INIT(name) {                    \
> > -       .mutex = __MUTEX_INITIALIZER(name.mutex),       \
> > -       .func = &name##_func,                           \
> > -       .progs = {},                                    \
> > -       .num_progs = 0,                                 \
> > -       .image = NULL,                                  \
> > -       .image_off = 0                                  \
> > +#define BPF_DISPATCHER_INIT(_name) {                           \
> > +       .mutex = __MUTEX_INITIALIZER(_name.mutex),              \
> > +       .func = &_name##_func,                                  \
> > +       .progs = {},                                            \
> > +       .num_progs = 0,                                         \
> > +       .image = NULL,                                          \
> > +       .image_off = 0,                                         \
> > +       .ksym = {                                               \
> > +               .name = #_name,                                 \
> > +               .lnode = LIST_HEAD_INIT(_name.ksym.lnode),      \
> > +       },                                                      \
> >  }
> >
> >  #define DEFINE_BPF_DISPATCHER(name)                                    \
> > diff --git a/kernel/bpf/dispatcher.c b/kernel/bpf/dispatcher.c
> > index b3e5b214fed8..8771d2cc5840 100644
> > --- a/kernel/bpf/dispatcher.c
> > +++ b/kernel/bpf/dispatcher.c
> > @@ -152,6 +152,12 @@ void bpf_dispatcher_change_prog(struct bpf_dispatcher *d, struct bpf_prog *from,
> >         if (!changed)
> >                 goto out;
> >
> > +       if (!prev_num_progs)
> > +               bpf_image_ksym_add(d->image, &d->ksym);
> > +
> > +       if (!d->num_progs)
> > +               bpf_ksym_del(&d->ksym);
> > +
> >         bpf_dispatcher_update(d, prev_num_progs);
> 
> On slightly unrelated note: seems like bpf_dispatcher_update won't
> propagate any lower-level errors back, which seems pretty bad as a
> bunch of stuff can go wrong.
> 
> Björn, was it a conscious decision or this just slipped through the cracks?
> 
> Jiri, reason I started looking at this was twofold:
> 1. you add/remove symbol before dispatcher is updated, which is
> different order from BPF trampoline updates. I think updating symbols
> after successful update makes more sense, no?

right, I guess I did not care, because there's no error returned
from bpf_dispatcher_update as you pointed out.. I'll check if we
can add that and add/del symbols afterwards

> 2. I was wondering if bpf_dispatcher_update() could return 0/1 (and <0
> on error, of course), depending on whether dispatcher is present or
> not. Though I'm not hard set on this.

yes, that might be a way.. I'll check

thanks,
jirka

Patch
diff mbox series

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index b91bac10d3ea..837cdc093d2c 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -520,6 +520,7 @@  struct bpf_dispatcher {
 	int num_progs;
 	void *image;
 	u32 image_off;
+	struct bpf_ksym ksym;
 };
 
 static __always_inline unsigned int bpf_dispatcher_nop_func(
@@ -535,13 +536,17 @@  struct bpf_trampoline *bpf_trampoline_lookup(u64 key);
 int bpf_trampoline_link_prog(struct bpf_prog *prog);
 int bpf_trampoline_unlink_prog(struct bpf_prog *prog);
 void bpf_trampoline_put(struct bpf_trampoline *tr);
-#define BPF_DISPATCHER_INIT(name) {			\
-	.mutex = __MUTEX_INITIALIZER(name.mutex),	\
-	.func = &name##_func,				\
-	.progs = {},					\
-	.num_progs = 0,					\
-	.image = NULL,					\
-	.image_off = 0					\
+#define BPF_DISPATCHER_INIT(_name) {				\
+	.mutex = __MUTEX_INITIALIZER(_name.mutex),		\
+	.func = &_name##_func,					\
+	.progs = {},						\
+	.num_progs = 0,						\
+	.image = NULL,						\
+	.image_off = 0,						\
+	.ksym = {						\
+		.name = #_name,					\
+		.lnode = LIST_HEAD_INIT(_name.ksym.lnode),	\
+	},							\
 }
 
 #define DEFINE_BPF_DISPATCHER(name)					\
diff --git a/kernel/bpf/dispatcher.c b/kernel/bpf/dispatcher.c
index b3e5b214fed8..8771d2cc5840 100644
--- a/kernel/bpf/dispatcher.c
+++ b/kernel/bpf/dispatcher.c
@@ -152,6 +152,12 @@  void bpf_dispatcher_change_prog(struct bpf_dispatcher *d, struct bpf_prog *from,
 	if (!changed)
 		goto out;
 
+	if (!prev_num_progs)
+		bpf_image_ksym_add(d->image, &d->ksym);
+
+	if (!d->num_progs)
+		bpf_ksym_del(&d->ksym);
+
 	bpf_dispatcher_update(d, prev_num_progs);
 out:
 	mutex_unlock(&d->mutex);