[PATCH] bpf: reduce compiler warnings by adding fallthrough comments

[PATCH] bpf: reduce compiler warnings by adding fallthrough comments

[Alexander Alemayhu]

Fixes the following warnings:

kernel/bpf/verifier.c: In function ‘may_access_direct_pkt_data’:
kernel/bpf/verifier.c:702:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
   if (t == BPF_WRITE)
      ^
kernel/bpf/verifier.c:704:2: note: here
  case BPF_PROG_TYPE_SCHED_CLS:
  ^~~~
kernel/bpf/verifier.c: In function ‘reg_set_min_max_inv’:
kernel/bpf/verifier.c:2057:23: warning: this statement may fall through [-Wimplicit-fallthrough=]
   true_reg->min_value = 0;
   ~~~~~~~~~~~~~~~~~~~~^~~
kernel/bpf/verifier.c:2058:2: note: here
  case BPF_JSGT:
  ^~~~
kernel/bpf/verifier.c:2068:23: warning: this statement may fall through [-Wimplicit-fallthrough=]
   true_reg->min_value = 0;
   ~~~~~~~~~~~~~~~~~~~~^~~
kernel/bpf/verifier.c:2069:2: note: here
  case BPF_JSGE:
  ^~~~
kernel/bpf/verifier.c: In function ‘reg_set_min_max’:
kernel/bpf/verifier.c:2009:24: warning: this statement may fall through [-Wimplicit-fallthrough=]
   false_reg->min_value = 0;
   ~~~~~~~~~~~~~~~~~~~~~^~~
kernel/bpf/verifier.c:2010:2: note: here
  case BPF_JSGT:
  ^~~~
kernel/bpf/verifier.c:2019:24: warning: this statement may fall through [-Wimplicit-fallthrough=]
   false_reg->min_value = 0;
   ~~~~~~~~~~~~~~~~~~~~~^~~
kernel/bpf/verifier.c:2020:2: note: here
  case BPF_JSGE:
  ^~~~

Reported-by: David Binderman <dcb314@hotmail.com>
Signed-off-by: Alexander Alemayhu <alexander@alemayhu.com>
---
Using gcc (GCC) 7.0.1 20170204 (Red Hat 7.0.1-0.6)

 kernel/bpf/verifier.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 1a754e5d2695..d2bded2b250c 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -701,6 +701,7 @@ static bool may_access_direct_pkt_data(struct bpf_verifier_env *env,
 		/* dst_input() and dst_output() can't write for now */
 		if (t == BPF_WRITE)
 			return false;
+		/* fallthrough */
 	case BPF_PROG_TYPE_SCHED_CLS:
 	case BPF_PROG_TYPE_SCHED_ACT:
 	case BPF_PROG_TYPE_XDP:
@@ -2007,6 +2008,7 @@ static void reg_set_min_max(struct bpf_reg_state *true_reg,
 	case BPF_JGT:
 		/* Unsigned comparison, the minimum value is 0. */
 		false_reg->min_value = 0;
+		/* fallthrough */
 	case BPF_JSGT:
 		/* If this is false then we know the maximum val is val,
 		 * otherwise we know the min val is val+1.
@@ -2017,6 +2019,7 @@ static void reg_set_min_max(struct bpf_reg_state *true_reg,
 	case BPF_JGE:
 		/* Unsigned comparison, the minimum value is 0. */
 		false_reg->min_value = 0;
+		/* fallthrough */
 	case BPF_JSGE:
 		/* If this is false then we know the maximum value is val - 1,
 		 * otherwise we know the mimimum value is val.
@@ -2055,6 +2058,7 @@ static void reg_set_min_max_inv(struct bpf_reg_state *true_reg,
 	case BPF_JGT:
 		/* Unsigned comparison, the minimum value is 0. */
 		true_reg->min_value = 0;
+		/* fallthrough */
 	case BPF_JSGT:
 		/*
 		 * If this is false, then the val is <= the register, if it is
@@ -2066,6 +2070,7 @@ static void reg_set_min_max_inv(struct bpf_reg_state *true_reg,
 	case BPF_JGE:
 		/* Unsigned comparison, the minimum value is 0. */
 		true_reg->min_value = 0;
+		/* fallthrough */
 	case BPF_JSGE:
 		/* If this is false then constant < register, if it is true then
 		 * the register < constant.
-- 
2.11.1

Re: [PATCH] bpf: reduce compiler warnings by adding fallthrough comments

[Daniel Borkmann]

On 02/14/2017 12:02 AM, Alexander Alemayhu wrote:
> Fixes the following warnings:
>
> kernel/bpf/verifier.c: In function ‘may_access_direct_pkt_data’:
> kernel/bpf/verifier.c:702:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
>     if (t == BPF_WRITE)
>        ^
> kernel/bpf/verifier.c:704:2: note: here
>    case BPF_PROG_TYPE_SCHED_CLS:
>    ^~~~
> kernel/bpf/verifier.c: In function ‘reg_set_min_max_inv’:
> kernel/bpf/verifier.c:2057:23: warning: this statement may fall through [-Wimplicit-fallthrough=]
>     true_reg->min_value = 0;
>     ~~~~~~~~~~~~~~~~~~~~^~~
> kernel/bpf/verifier.c:2058:2: note: here
>    case BPF_JSGT:
>    ^~~~
> kernel/bpf/verifier.c:2068:23: warning: this statement may fall through [-Wimplicit-fallthrough=]
>     true_reg->min_value = 0;
>     ~~~~~~~~~~~~~~~~~~~~^~~
> kernel/bpf/verifier.c:2069:2: note: here
>    case BPF_JSGE:
>    ^~~~
> kernel/bpf/verifier.c: In function ‘reg_set_min_max’:
> kernel/bpf/verifier.c:2009:24: warning: this statement may fall through [-Wimplicit-fallthrough=]
>     false_reg->min_value = 0;
>     ~~~~~~~~~~~~~~~~~~~~~^~~
> kernel/bpf/verifier.c:2010:2: note: here
>    case BPF_JSGT:
>    ^~~~
> kernel/bpf/verifier.c:2019:24: warning: this statement may fall through [-Wimplicit-fallthrough=]
>     false_reg->min_value = 0;
>     ~~~~~~~~~~~~~~~~~~~~~^~~
> kernel/bpf/verifier.c:2020:2: note: here
>    case BPF_JSGE:
>    ^~~~
>
> Reported-by: David Binderman <dcb314@hotmail.com>
> Signed-off-by: Alexander Alemayhu <alexander@alemayhu.com>

These fall-through comments are fine for net-next tree.

Acked-by: Daniel Borkmann <daniel@iogearbox.net>

Re: [PATCH] bpf: reduce compiler warnings by adding fallthrough comments

[Alexei Starovoitov]

On Tue, Feb 14, 2017 at 12:18:05AM +0100, Daniel Borkmann wrote:
> >kernel/bpf/verifier.c:2019:24: warning: this statement may fall through [-Wimplicit-fallthrough=]
> >    false_reg->min_value = 0;
> >    ~~~~~~~~~~~~~~~~~~~~~^~~
> >
> >Reported-by: David Binderman <dcb314@hotmail.com>
> >Signed-off-by: Alexander Alemayhu <alexander@alemayhu.com>
> 
> These fall-through comments are fine for net-next tree.
> 
> Acked-by: Daniel Borkmann <daniel@iogearbox.net>

lgtm as well
Acked-by: Alexei Starovoitov <ast@kernel.org>

Re: [PATCH] bpf: reduce compiler warnings by adding fallthrough comments

[David Miller]

From: Alexander Alemayhu <alexander@alemayhu.com>
Date: Tue, 14 Feb 2017 00:02:35 +0100

> Fixes the following warnings:
 ...
> Reported-by: David Binderman <dcb314@hotmail.com>
> Signed-off-by: Alexander Alemayhu <alexander@alemayhu.com>

Applied, thank you.