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* [PATCH bpf-next v2 0/2] BPF Ringbuffer + Sleepable Programs
@ 2021-02-04 19:36 KP Singh
  2021-02-04 19:36 ` [PATCH bpf-next v2 1/2] bpf: Allow usage of BPF ringbuffer in sleepable programs KP Singh
                   ` (2 more replies)
  0 siblings, 3 replies; 6+ messages in thread
From: KP Singh @ 2021-02-04 19:36 UTC (permalink / raw)
  To: bpf
  Cc: Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko,
	Florent Revest, Brendan Jackman

# v1 -> v2

- Use ring_buffer__consume without BPF_RB_FORCE_WAKEUP as suggested by
  Andrii
- Use ASSERT_OK_PTR macro

Sleepable programs currently do not have access to any ringbuffer and
since the perf ring buffer is a per-cpu map, it would not be trivial to
enable for sleepable programs. Our specific use-case is to use the
bpf_ima_inode_hash helper and write the hash to a ring buffer from a
sleepable LSM hook.

This series allows the BPF ringbuffer to be used in sleepable programs
(tracing and lsm). Since the helper prototypes were already exposed
the only change required was have the verifier allow
BPF_MAP_TYPE_RINGBUF for sleepable programs. The ima test is also
modified to use the ringbuffer instead of global variables.

Based on dicussions we had over the BPF office hours and enabling all
the possible debug options, I could not find any issues or warnings when
using the ring buffer from sleepable programs.



KP Singh (2):
  bpf: Allow usage of BPF ringbuffer in sleepable programs
  bpf/selftests: Update the IMA test to use BPF ring buffer

 kernel/bpf/verifier.c                         |  2 ++
 .../selftests/bpf/prog_tests/test_ima.c       | 23 ++++++++++---
 tools/testing/selftests/bpf/progs/ima.c       | 33 ++++++++++++++-----
 3 files changed, 45 insertions(+), 13 deletions(-)

-- 
2.30.0.365.g02bc693789-goog


^ permalink raw reply	[flat|nested] 6+ messages in thread

* [PATCH bpf-next v2 1/2] bpf: Allow usage of BPF ringbuffer in sleepable programs
  2021-02-04 19:36 [PATCH bpf-next v2 0/2] BPF Ringbuffer + Sleepable Programs KP Singh
@ 2021-02-04 19:36 ` KP Singh
  2021-02-04 20:57   ` Song Liu
  2021-02-04 19:36 ` [PATCH bpf-next v2 2/2] bpf/selftests: Update the IMA test to use BPF ring buffer KP Singh
  2021-02-05  7:06 ` [PATCH bpf-next v2 0/2] BPF Ringbuffer + Sleepable Programs Andrii Nakryiko
  2 siblings, 1 reply; 6+ messages in thread
From: KP Singh @ 2021-02-04 19:36 UTC (permalink / raw)
  To: bpf
  Cc: Andrii Nakryiko, Alexei Starovoitov, Daniel Borkmann,
	Florent Revest, Brendan Jackman

The BPF ringbuffer map is pre-allocated and the implementation logic
does not rely on disabling preemption or per-cpu data structures. Using
the BPF ringbuffer sleepable LSM and tracing programs does not trigger
any warnings with DEBUG_ATOMIC_SLEEP, DEBUG_PREEMPT,
PROVE_RCU and PROVE_LOCKING and LOCKDEP enabled.

This allows helpers like bpf_copy_from_user and bpf_ima_inode_hash to
write to the BPF ring buffer from sleepable BPF programs.

Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: KP Singh <kpsingh@kernel.org>
---
 kernel/bpf/verifier.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 5e09632efddb..4c33b4840438 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -10024,6 +10024,8 @@ static int check_map_prog_compatibility(struct bpf_verifier_env *env,
 				return -EINVAL;
 			}
 			break;
+		case BPF_MAP_TYPE_RINGBUF:
+			break;
 		default:
 			verbose(env,
 				"Sleepable programs can only use array and hash maps\n");
-- 
2.30.0.365.g02bc693789-goog


^ permalink raw reply	[flat|nested] 6+ messages in thread

* [PATCH bpf-next v2 2/2] bpf/selftests: Update the IMA test to use BPF ring buffer
  2021-02-04 19:36 [PATCH bpf-next v2 0/2] BPF Ringbuffer + Sleepable Programs KP Singh
  2021-02-04 19:36 ` [PATCH bpf-next v2 1/2] bpf: Allow usage of BPF ringbuffer in sleepable programs KP Singh
@ 2021-02-04 19:36 ` KP Singh
  2021-02-05  7:06 ` [PATCH bpf-next v2 0/2] BPF Ringbuffer + Sleepable Programs Andrii Nakryiko
  2 siblings, 0 replies; 6+ messages in thread
From: KP Singh @ 2021-02-04 19:36 UTC (permalink / raw)
  To: bpf
  Cc: Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko,
	Florent Revest, Brendan Jackman

Instead of using shared global variables between userspace and BPF, use
the ring buffer to send the IMA hash on the BPF ring buffer. This helps
in validating both IMA and the usage of the ringbuffer in sleepable
programs.

Signed-off-by: KP Singh <kpsingh@kernel.org>
---
 .../selftests/bpf/prog_tests/test_ima.c       | 23 ++++++++++---
 tools/testing/selftests/bpf/progs/ima.c       | 33 ++++++++++++++-----
 2 files changed, 43 insertions(+), 13 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/test_ima.c b/tools/testing/selftests/bpf/prog_tests/test_ima.c
index 61fca681d524..b54bc0c351b7 100644
--- a/tools/testing/selftests/bpf/prog_tests/test_ima.c
+++ b/tools/testing/selftests/bpf/prog_tests/test_ima.c
@@ -9,6 +9,7 @@
 #include <unistd.h>
 #include <sys/wait.h>
 #include <test_progs.h>
+#include <linux/ring_buffer.h>
 
 #include "ima.skel.h"
 
@@ -31,9 +32,18 @@ static int run_measured_process(const char *measured_dir, u32 *monitored_pid)
 	return -EINVAL;
 }
 
+static u64 ima_hash_from_bpf;
+
+static int process_sample(void *ctx, void *data, size_t len)
+{
+	ima_hash_from_bpf = *((u64 *)data);
+	return 0;
+}
+
 void test_test_ima(void)
 {
 	char measured_dir_template[] = "/tmp/ima_measuredXXXXXX";
+	struct ring_buffer *ringbuf;
 	const char *measured_dir;
 	char cmd[256];
 
@@ -44,6 +54,11 @@ void test_test_ima(void)
 	if (CHECK(!skel, "skel_load", "skeleton failed\n"))
 		goto close_prog;
 
+	ringbuf = ring_buffer__new(bpf_map__fd(skel->maps.ringbuf),
+				   process_sample, NULL, NULL);
+	if (!ASSERT_OK_PTR(ringbuf, "ringbuf"))
+		goto close_prog;
+
 	err = ima__attach(skel);
 	if (CHECK(err, "attach", "attach failed: %d\n", err))
 		goto close_prog;
@@ -60,11 +75,9 @@ void test_test_ima(void)
 	if (CHECK(err, "run_measured_process", "err = %d\n", err))
 		goto close_clean;
 
-	CHECK(skel->data->ima_hash_ret < 0, "ima_hash_ret",
-	      "ima_hash_ret = %ld\n", skel->data->ima_hash_ret);
-
-	CHECK(skel->bss->ima_hash == 0, "ima_hash",
-	      "ima_hash = %lu\n", skel->bss->ima_hash);
+	err = ring_buffer__consume(ringbuf);
+	ASSERT_EQ(err, 1, "num_samples_or_err");
+	ASSERT_NEQ(ima_hash_from_bpf, 0, "ima_hash");
 
 close_clean:
 	snprintf(cmd, sizeof(cmd), "./ima_setup.sh cleanup %s", measured_dir);
diff --git a/tools/testing/selftests/bpf/progs/ima.c b/tools/testing/selftests/bpf/progs/ima.c
index 86b21aff4bc5..96060ff4ffc6 100644
--- a/tools/testing/selftests/bpf/progs/ima.c
+++ b/tools/testing/selftests/bpf/progs/ima.c
@@ -9,20 +9,37 @@
 #include <bpf/bpf_helpers.h>
 #include <bpf/bpf_tracing.h>
 
-long ima_hash_ret = -1;
-u64 ima_hash = 0;
 u32 monitored_pid = 0;
 
+struct {
+	__uint(type, BPF_MAP_TYPE_RINGBUF);
+	__uint(max_entries, 1 << 12);
+} ringbuf SEC(".maps");
+
 char _license[] SEC("license") = "GPL";
 
 SEC("lsm.s/bprm_committed_creds")
-int BPF_PROG(ima, struct linux_binprm *bprm)
+void BPF_PROG(ima, struct linux_binprm *bprm)
 {
-	u32 pid = bpf_get_current_pid_tgid() >> 32;
+	u64 ima_hash = 0;
+	u64 *sample;
+	int ret;
+	u32 pid;
+
+	pid = bpf_get_current_pid_tgid() >> 32;
+	if (pid == monitored_pid) {
+		ret = bpf_ima_inode_hash(bprm->file->f_inode, &ima_hash,
+					 sizeof(ima_hash));
+		if (ret < 0 || ima_hash == 0)
+			return;
+
+		sample = bpf_ringbuf_reserve(&ringbuf, sizeof(u64), 0);
+		if (!sample)
+			return;
 
-	if (pid == monitored_pid)
-		ima_hash_ret = bpf_ima_inode_hash(bprm->file->f_inode,
-						  &ima_hash, sizeof(ima_hash));
+		*sample = ima_hash;
+		bpf_ringbuf_submit(sample, 0);
+	}
 
-	return 0;
+	return;
 }
-- 
2.30.0.365.g02bc693789-goog


^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [PATCH bpf-next v2 1/2] bpf: Allow usage of BPF ringbuffer in sleepable programs
  2021-02-04 19:36 ` [PATCH bpf-next v2 1/2] bpf: Allow usage of BPF ringbuffer in sleepable programs KP Singh
@ 2021-02-04 20:57   ` Song Liu
  2021-02-05  1:15     ` Andrii Nakryiko
  0 siblings, 1 reply; 6+ messages in thread
From: Song Liu @ 2021-02-04 20:57 UTC (permalink / raw)
  To: KP Singh
  Cc: bpf, Andrii Nakryiko, Alexei Starovoitov, Daniel Borkmann,
	Florent Revest, Brendan Jackman

On Thu, Feb 4, 2021 at 11:39 AM KP Singh <kpsingh@kernel.org> wrote:
>
> The BPF ringbuffer map is pre-allocated and the implementation logic
> does not rely on disabling preemption or per-cpu data structures. Using
> the BPF ringbuffer sleepable LSM and tracing programs does not trigger
> any warnings with DEBUG_ATOMIC_SLEEP, DEBUG_PREEMPT,
> PROVE_RCU and PROVE_LOCKING and LOCKDEP enabled.
>
> This allows helpers like bpf_copy_from_user and bpf_ima_inode_hash to
> write to the BPF ring buffer from sleepable BPF programs.
>
> Acked-by: Andrii Nakryiko <andrii@kernel.org>
> Signed-off-by: KP Singh <kpsingh@kernel.org>
> ---
>  kernel/bpf/verifier.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index 5e09632efddb..4c33b4840438 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -10024,6 +10024,8 @@ static int check_map_prog_compatibility(struct bpf_verifier_env *env,
>                                 return -EINVAL;
>                         }
>                         break;
> +               case BPF_MAP_TYPE_RINGBUF:
> +                       break;
>                 default:
>                         verbose(env,
>                                 "Sleepable programs can only use array and hash maps\n");

Shall we update this message?

Thanks,
Song

> --
> 2.30.0.365.g02bc693789-goog
>

^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [PATCH bpf-next v2 1/2] bpf: Allow usage of BPF ringbuffer in sleepable programs
  2021-02-04 20:57   ` Song Liu
@ 2021-02-05  1:15     ` Andrii Nakryiko
  0 siblings, 0 replies; 6+ messages in thread
From: Andrii Nakryiko @ 2021-02-05  1:15 UTC (permalink / raw)
  To: Song Liu
  Cc: KP Singh, bpf, Andrii Nakryiko, Alexei Starovoitov,
	Daniel Borkmann, Florent Revest, Brendan Jackman

On Thu, Feb 4, 2021 at 12:57 PM Song Liu <song@kernel.org> wrote:
>
> On Thu, Feb 4, 2021 at 11:39 AM KP Singh <kpsingh@kernel.org> wrote:
> >
> > The BPF ringbuffer map is pre-allocated and the implementation logic
> > does not rely on disabling preemption or per-cpu data structures. Using
> > the BPF ringbuffer sleepable LSM and tracing programs does not trigger
> > any warnings with DEBUG_ATOMIC_SLEEP, DEBUG_PREEMPT,
> > PROVE_RCU and PROVE_LOCKING and LOCKDEP enabled.
> >
> > This allows helpers like bpf_copy_from_user and bpf_ima_inode_hash to
> > write to the BPF ring buffer from sleepable BPF programs.
> >
> > Acked-by: Andrii Nakryiko <andrii@kernel.org>
> > Signed-off-by: KP Singh <kpsingh@kernel.org>
> > ---
> >  kernel/bpf/verifier.c | 2 ++
> >  1 file changed, 2 insertions(+)
> >
> > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> > index 5e09632efddb..4c33b4840438 100644
> > --- a/kernel/bpf/verifier.c
> > +++ b/kernel/bpf/verifier.c
> > @@ -10024,6 +10024,8 @@ static int check_map_prog_compatibility(struct bpf_verifier_env *env,
> >                                 return -EINVAL;
> >                         }
> >                         break;
> > +               case BPF_MAP_TYPE_RINGBUF:
> > +                       break;
> >                 default:
> >                         verbose(env,
> >                                 "Sleepable programs can only use array and hash maps\n");
>
> Shall we update this message?
>

I fixed it up while applying. Thanks for staying alert!

> Thanks,
> Song
>
> > --
> > 2.30.0.365.g02bc693789-goog
> >

^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [PATCH bpf-next v2 0/2] BPF Ringbuffer + Sleepable Programs
  2021-02-04 19:36 [PATCH bpf-next v2 0/2] BPF Ringbuffer + Sleepable Programs KP Singh
  2021-02-04 19:36 ` [PATCH bpf-next v2 1/2] bpf: Allow usage of BPF ringbuffer in sleepable programs KP Singh
  2021-02-04 19:36 ` [PATCH bpf-next v2 2/2] bpf/selftests: Update the IMA test to use BPF ring buffer KP Singh
@ 2021-02-05  7:06 ` Andrii Nakryiko
  2 siblings, 0 replies; 6+ messages in thread
From: Andrii Nakryiko @ 2021-02-05  7:06 UTC (permalink / raw)
  To: KP Singh
  Cc: bpf, Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko,
	Florent Revest, Brendan Jackman

On Thu, Feb 4, 2021 at 11:36 AM KP Singh <kpsingh@kernel.org> wrote:
>
> # v1 -> v2
>
> - Use ring_buffer__consume without BPF_RB_FORCE_WAKEUP as suggested by
>   Andrii
> - Use ASSERT_OK_PTR macro
>
> Sleepable programs currently do not have access to any ringbuffer and
> since the perf ring buffer is a per-cpu map, it would not be trivial to
> enable for sleepable programs. Our specific use-case is to use the
> bpf_ima_inode_hash helper and write the hash to a ring buffer from a
> sleepable LSM hook.
>
> This series allows the BPF ringbuffer to be used in sleepable programs
> (tracing and lsm). Since the helper prototypes were already exposed
> the only change required was have the verifier allow
> BPF_MAP_TYPE_RINGBUF for sleepable programs. The ima test is also
> modified to use the ringbuffer instead of global variables.
>
> Based on dicussions we had over the BPF office hours and enabling all
> the possible debug options, I could not find any issues or warnings when
> using the ring buffer from sleepable programs.
>
>
>
> KP Singh (2):
>   bpf: Allow usage of BPF ringbuffer in sleepable programs
>   bpf/selftests: Update the IMA test to use BPF ring buffer
>
>  kernel/bpf/verifier.c                         |  2 ++
>  .../selftests/bpf/prog_tests/test_ima.c       | 23 ++++++++++---
>  tools/testing/selftests/bpf/progs/ima.c       | 33 ++++++++++++++-----
>  3 files changed, 45 insertions(+), 13 deletions(-)
>
> --
> 2.30.0.365.g02bc693789-goog
>

Bot didn't send a notification. This was applied to bpf-next.

^ permalink raw reply	[flat|nested] 6+ messages in thread

end of thread, other threads:[~2021-02-05  7:08 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-02-04 19:36 [PATCH bpf-next v2 0/2] BPF Ringbuffer + Sleepable Programs KP Singh
2021-02-04 19:36 ` [PATCH bpf-next v2 1/2] bpf: Allow usage of BPF ringbuffer in sleepable programs KP Singh
2021-02-04 20:57   ` Song Liu
2021-02-05  1:15     ` Andrii Nakryiko
2021-02-04 19:36 ` [PATCH bpf-next v2 2/2] bpf/selftests: Update the IMA test to use BPF ring buffer KP Singh
2021-02-05  7:06 ` [PATCH bpf-next v2 0/2] BPF Ringbuffer + Sleepable Programs Andrii Nakryiko

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