[PATCH] bpf: test_bpf: turn of preemption in function __run_once

When running test seccomp_bpf the following splat occurs:

[ RUN      ] global.secseccomp_bpf.c:2136:global.detect_seccomp_filter_flags:Expected 22 (22) == (*__errno_location ()) (14)
seccomp_bpf.c:2138:global.detect_seccomp_filter_flags:Failed to detect that an unknown
  filter flag (0x8) is unsupported! Does a new flag need to be added to this test?
[ 2155.677841] BUG: assuming atomic context at kernel/seccomp.c:271
[ 2155.689351] in_atomic(): 0, irqs_disabled(): 0, pid: 28540, name: seccomp_bpf
[ 2155.696597] INFO: lockdep is turned off.
[ 2155.700605] CPU: 5 PID: 28540 Comm: seccomp_bpf Tainted: G        W         5.0.0-rc7-next-20190220 #1
[ 2155.709972] Hardware name: HiKey Development Board (DT)
[ 2155.715232] Call trace:
[ 2155.717710]  dump_backtrace+0x0/0x160
[ 2155.721399]  show_stack+0x24/0x30
[ 2155.724742]  dump_stack+0xc8/0x114
[ 2155.728172]  __cant_sleep+0xf0/0x108
[ 2155.731777]  __seccomp_filter+0x8c/0x5c8
[ 2155.735727]  __secure_computing+0x4c/0xe8
[ 2155.739767]  syscall_trace_enter+0xf8/0x2b8
[ 2155.743982]  el0_svc_common+0xf0/0x130
[ 2155.747758]  el0_svc_handler+0x38/0x78
[ 2155.751534]  el0_svc+0x8/0xc

Rework so that preemption is disabled when we loop over function
'BPF_PROG_RUN(...)'.
Commit 568f196756ad ("bpf: check that BPF programs run with preemption disabled")
highlighted the issue.

Suggested-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Anders Roxell <redacted>
---
 lib/test_bpf.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/lib/test_bpf.c b/lib/test_bpf.c
index f3e570722a7e..0845f635f404 100644
--- a/lib/test_bpf.c
+++ b/lib/test_bpf.c

@@ -6668,12 +6668,14 @@ static int __run_one(const struct bpf_prog *fp, const void *data,
 	u64 start, finish;
 	int ret = 0, i;
 
+	preempt_disable();
 	start = ktime_get_ns();
 
 	for (i = 0; i < runs; i++)
 		ret = BPF_PROG_RUN(fp, data);
 
 	finish = ktime_get_ns();
+	preempt_enable();
 
 	*duration = finish - start;
 	do_div(*duration, runs);

-- 
2.11.0

On 02/21/2019 09:44 AM, Anders Roxell wrote:

When running test seccomp_bpf the following splat occurs:

[ RUN      ] global.secseccomp_bpf.c:2136:global.detect_seccomp_filter_flags:Expected 22 (22) == (*__errno_location ()) (14)
seccomp_bpf.c:2138:global.detect_seccomp_filter_flags:Failed to detect that an unknown
  filter flag (0x8) is unsupported! Does a new flag need to be added to this test?
[ 2155.677841] BUG: assuming atomic context at kernel/seccomp.c:271
[ 2155.689351] in_atomic(): 0, irqs_disabled(): 0, pid: 28540, name: seccomp_bpf
[ 2155.696597] INFO: lockdep is turned off.
[ 2155.700605] CPU: 5 PID: 28540 Comm: seccomp_bpf Tainted: G        W         5.0.0-rc7-next-20190220 #1
[ 2155.709972] Hardware name: HiKey Development Board (DT)
[ 2155.715232] Call trace:
[ 2155.717710]  dump_backtrace+0x0/0x160
[ 2155.721399]  show_stack+0x24/0x30
[ 2155.724742]  dump_stack+0xc8/0x114
[ 2155.728172]  __cant_sleep+0xf0/0x108
[ 2155.731777]  __seccomp_filter+0x8c/0x5c8
[ 2155.735727]  __secure_computing+0x4c/0xe8
[ 2155.739767]  syscall_trace_enter+0xf8/0x2b8
[ 2155.743982]  el0_svc_common+0xf0/0x130
[ 2155.747758]  el0_svc_handler+0x38/0x78
[ 2155.751534]  el0_svc+0x8/0xc

Rework so that preemption is disabled when we loop over function
'BPF_PROG_RUN(...)'.
Commit 568f196756ad ("bpf: check that BPF programs run with preemption disabled")
highlighted the issue.

Suggested-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Anders Roxell <redacted>

Hmm, wrong commit description? Below code is not related to seccomp
but rather BPF test suite. Could you fix it up and resubmit? Rest
looks okay to me.

On Thu, 21 Feb 2019 at 16:38, Daniel Borkmann [off-list ref] wrote:

On 02/21/2019 09:44 AM, Anders Roxell wrote:

quoted

When running test seccomp_bpf the following splat occurs:

[ RUN      ] global.secseccomp_bpf.c:2136:global.detect_seccomp_filter_flags:Expected 22 (22) == (*__errno_location ()) (14)
seccomp_bpf.c:2138:global.detect_seccomp_filter_flags:Failed to detect that an unknown
  filter flag (0x8) is unsupported! Does a new flag need to be added to this test?
[ 2155.677841] BUG: assuming atomic context at kernel/seccomp.c:271
[ 2155.689351] in_atomic(): 0, irqs_disabled(): 0, pid: 28540, name: seccomp_bpf
[ 2155.696597] INFO: lockdep is turned off.
[ 2155.700605] CPU: 5 PID: 28540 Comm: seccomp_bpf Tainted: G        W         5.0.0-rc7-next-20190220 #1
[ 2155.709972] Hardware name: HiKey Development Board (DT)
[ 2155.715232] Call trace:
[ 2155.717710]  dump_backtrace+0x0/0x160
[ 2155.721399]  show_stack+0x24/0x30
[ 2155.724742]  dump_stack+0xc8/0x114
[ 2155.728172]  __cant_sleep+0xf0/0x108
[ 2155.731777]  __seccomp_filter+0x8c/0x5c8
[ 2155.735727]  __secure_computing+0x4c/0xe8
[ 2155.739767]  syscall_trace_enter+0xf8/0x2b8
[ 2155.743982]  el0_svc_common+0xf0/0x130
[ 2155.747758]  el0_svc_handler+0x38/0x78
[ 2155.751534]  el0_svc+0x8/0xc

Rework so that preemption is disabled when we loop over function
'BPF_PROG_RUN(...)'.
Commit 568f196756ad ("bpf: check that BPF programs run with preemption disabled")
highlighted the issue.

Suggested-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Anders Roxell <redacted>

Hmm, wrong commit description?

urgh, you are correct. I'm sorry.
Sending a v2 shortly.

Below code is not related to seccomp
but rather BPF test suite. Could you fix it up and resubmit? Rest
looks okay to me.

quoted

---
 lib/test_bpf.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/lib/test_bpf.c b/lib/test_bpf.c
index f3e570722a7e..0845f635f404 100644
--- a/lib/test_bpf.c
+++ b/lib/test_bpf.c

@@ -6668,12 +6668,14 @@ static int __run_one(const struct bpf_prog *fp, const void *data,
      u64 start, finish;
      int ret = 0, i;

+     preempt_disable();
      start = ktime_get_ns();

      for (i = 0; i < runs; i++)
              ret = BPF_PROG_RUN(fp, data);

      finish = ktime_get_ns();
+     preempt_enable();

      *duration = finish - start;
      do_div(*duration, runs);