[bpf-next,2/2] selftests/bpf: add loop test 5

Add a test with multiple exit conditions.
It's not an infinite loop only when the verifier can properly track
all math on variable 'i' through all possible ways of executing this loop.

barrier()s are needed to disable llvm optimization that combines multiple
branches into fewer branches.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---
 .../bpf/prog_tests/bpf_verif_scale.c          |  1 +
 tools/testing/selftests/bpf/progs/loop5.c     | 37 +++++++++++++++++++
 2 files changed, 38 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/progs/loop5.c

On 8/2/19 4:33 PM, Alexei Starovoitov wrote:
> Add a test with multiple exit conditions.
> It's not an infinite loop only when the verifier can properly track
> all math on variable 'i' through all possible ways of executing this loop.

Agreed with motivation of this test.

> 
> barrier()s are needed to disable llvm optimization that combines multiple
> branches into fewer branches.
> 
> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
> ---
>   .../bpf/prog_tests/bpf_verif_scale.c          |  1 +
>   tools/testing/selftests/bpf/progs/loop5.c     | 37 +++++++++++++++++++
>   2 files changed, 38 insertions(+)
>   create mode 100644 tools/testing/selftests/bpf/progs/loop5.c
> 
> diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_verif_scale.c b/tools/testing/selftests/bpf/prog_tests/bpf_verif_scale.c
> index 757e39540eda..29615a4a9362 100644
> --- a/tools/testing/selftests/bpf/prog_tests/bpf_verif_scale.c
> +++ b/tools/testing/selftests/bpf/prog_tests/bpf_verif_scale.c
> @@ -72,6 +72,7 @@ void test_bpf_verif_scale(void)
>   		{ "loop1.o", BPF_PROG_TYPE_RAW_TRACEPOINT },
>   		{ "loop2.o", BPF_PROG_TYPE_RAW_TRACEPOINT },
>   		{ "loop4.o", BPF_PROG_TYPE_RAW_TRACEPOINT }, > +		{ "loop5.o", BPF_PROG_TYPE_RAW_TRACEPOINT },

More like a BPF_PROG_TYPE_SCHED_CLS type although probably it does not 
matter as we did not attach it to anywhere?

>   
>   		/* partial unroll. 19k insn in a loop.
>   		 * Total program size 20.8k insn.
> diff --git a/tools/testing/selftests/bpf/progs/loop5.c b/tools/testing/selftests/bpf/progs/loop5.c
> new file mode 100644
> index 000000000000..9d9817efe208
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/loop5.c
> @@ -0,0 +1,37 @@
> +// SPDX-License-Identifier: GPL-2.0
> +// Copyright (c) 2019 Facebook
> +#include <linux/sched.h>
> +#include <linux/ptrace.h>

The above headers probably not needed.

> +#include <stdint.h>
> +#include <stddef.h>
> +#include <stdbool.h>
> +#include <linux/bpf.h>
> +#include "bpf_helpers.h"
> +#define barrier() __asm__ __volatile__("": : :"memory")
> +
> +char _license[] SEC("license") = "GPL";
> +
> +SEC("socket")
> +int while_true(volatile struct __sk_buff* skb)
> +{
> +	int i = 0;
> +
> +	while (true) {
> +		if (skb->len)
> +			i += 3;
> +		else
> +			i += 7;
> +		if (i == 9)
> +			break;
> +		barrier();
> +		if (i == 10)
> +			break;
> +		barrier();
> +		if (i == 13)
> +			break;
> +		barrier();
> +		if (i == 14)
> +			break;
> +	}
> +	return i;
> +}
>

On Sun, Aug 04, 2019 at 05:45:23AM +0000, Yonghong Song wrote:
> 
> 
> On 8/2/19 4:33 PM, Alexei Starovoitov wrote:
> > Add a test with multiple exit conditions.
> > It's not an infinite loop only when the verifier can properly track
> > all math on variable 'i' through all possible ways of executing this loop.
> 
> Agreed with motivation of this test.
> 
> > 
> > barrier()s are needed to disable llvm optimization that combines multiple
> > branches into fewer branches.
> > 
> > Signed-off-by: Alexei Starovoitov <ast@kernel.org>
> > ---
> >   .../bpf/prog_tests/bpf_verif_scale.c          |  1 +
> >   tools/testing/selftests/bpf/progs/loop5.c     | 37 +++++++++++++++++++
> >   2 files changed, 38 insertions(+)
> >   create mode 100644 tools/testing/selftests/bpf/progs/loop5.c
> > 
> > diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_verif_scale.c b/tools/testing/selftests/bpf/prog_tests/bpf_verif_scale.c
> > index 757e39540eda..29615a4a9362 100644
> > --- a/tools/testing/selftests/bpf/prog_tests/bpf_verif_scale.c
> > +++ b/tools/testing/selftests/bpf/prog_tests/bpf_verif_scale.c
> > @@ -72,6 +72,7 @@ void test_bpf_verif_scale(void)
> >   		{ "loop1.o", BPF_PROG_TYPE_RAW_TRACEPOINT },
> >   		{ "loop2.o", BPF_PROG_TYPE_RAW_TRACEPOINT },
> >   		{ "loop4.o", BPF_PROG_TYPE_RAW_TRACEPOINT }, > +		{ "loop5.o", BPF_PROG_TYPE_RAW_TRACEPOINT },
> 
> More like a BPF_PROG_TYPE_SCHED_CLS type although probably it does not 
> matter as we did not attach it to anywhere?

right. will fix.

> >   
> >   		/* partial unroll. 19k insn in a loop.
> >   		 * Total program size 20.8k insn.
> > diff --git a/tools/testing/selftests/bpf/progs/loop5.c b/tools/testing/selftests/bpf/progs/loop5.c
> > new file mode 100644
> > index 000000000000..9d9817efe208
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/progs/loop5.c
> > @@ -0,0 +1,37 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +// Copyright (c) 2019 Facebook
> > +#include <linux/sched.h>
> > +#include <linux/ptrace.h>
> 
> The above headers probably not needed.

will fix