[PATCH] bpf/core.c - silence warning messages

[PATCH] bpf/core.c - silence warning messages

[Valdis Klētnieks]

Compiling kernel/bpf/core.c with W=1 causes a flood of warnings:

kernel/bpf/core.c:1198:65: warning: initialized field overwritten [-Woverride-init]
 1198 | #define BPF_INSN_3_TBL(x, y, z) [BPF_##x | BPF_##y | BPF_##z] = true
      |                                                                 ^~~~
kernel/bpf/core.c:1087:2: note: in expansion of macro 'BPF_INSN_3_TBL'
 1087 |  INSN_3(ALU, ADD,  X),   \
      |  ^~~~~~
kernel/bpf/core.c:1202:3: note: in expansion of macro 'BPF_INSN_MAP'
 1202 |   BPF_INSN_MAP(BPF_INSN_2_TBL, BPF_INSN_3_TBL),
      |   ^~~~~~~~~~~~
kernel/bpf/core.c:1198:65: note: (near initialization for 'public_insntable[12]')
 1198 | #define BPF_INSN_3_TBL(x, y, z) [BPF_##x | BPF_##y | BPF_##z] = true
      |                                                                 ^~~~
kernel/bpf/core.c:1087:2: note: in expansion of macro 'BPF_INSN_3_TBL'
 1087 |  INSN_3(ALU, ADD,  X),   \
      |  ^~~~~~
kernel/bpf/core.c:1202:3: note: in expansion of macro 'BPF_INSN_MAP'
 1202 |   BPF_INSN_MAP(BPF_INSN_2_TBL, BPF_INSN_3_TBL),
      |   ^~~~~~~~~~~~

98 copies of the above.

The attached patch silences the warnings, because we *know* we're overwriting
the default initializer. That leaves bpf/core.c with only 6 other warnings,
which become more visible in comparison.

Signed-off-by: Valdis Kletnieks <valdis.kletnieks@vt.edu>

diff --git a/kernel/bpf/Makefile b/kernel/bpf/Makefile
index 4c2fa3ac56f6..2606665f2cb5 100644
--- a/kernel/bpf/Makefile
+++ b/kernel/bpf/Makefile
@@ -21,3 +21,4 @@ obj-$(CONFIG_CGROUP_BPF) += cgroup.o
 ifeq ($(CONFIG_INET),y)
 obj-$(CONFIG_BPF_SYSCALL) += reuseport_array.o
 endif
+CFLAGS_core.o          += $(call cc-disable-warning, override-init)

Re: [PATCH] bpf/core.c - silence warning messages

[Andrii Nakryiko]

On Thu, Jun 6, 2019 at 8:08 PM Valdis Klētnieks <valdis.kletnieks@vt.edu> wrote:
>
> Compiling kernel/bpf/core.c with W=1 causes a flood of warnings:
>
> kernel/bpf/core.c:1198:65: warning: initialized field overwritten [-Woverride-init]
>  1198 | #define BPF_INSN_3_TBL(x, y, z) [BPF_##x | BPF_##y | BPF_##z] = true
>       |                                                                 ^~~~
> kernel/bpf/core.c:1087:2: note: in expansion of macro 'BPF_INSN_3_TBL'
>  1087 |  INSN_3(ALU, ADD,  X),   \
>       |  ^~~~~~
> kernel/bpf/core.c:1202:3: note: in expansion of macro 'BPF_INSN_MAP'
>  1202 |   BPF_INSN_MAP(BPF_INSN_2_TBL, BPF_INSN_3_TBL),
>       |   ^~~~~~~~~~~~
> kernel/bpf/core.c:1198:65: note: (near initialization for 'public_insntable[12]')
>  1198 | #define BPF_INSN_3_TBL(x, y, z) [BPF_##x | BPF_##y | BPF_##z] = true
>       |                                                                 ^~~~
> kernel/bpf/core.c:1087:2: note: in expansion of macro 'BPF_INSN_3_TBL'
>  1087 |  INSN_3(ALU, ADD,  X),   \
>       |  ^~~~~~
> kernel/bpf/core.c:1202:3: note: in expansion of macro 'BPF_INSN_MAP'
>  1202 |   BPF_INSN_MAP(BPF_INSN_2_TBL, BPF_INSN_3_TBL),
>       |   ^~~~~~~~~~~~
>
> 98 copies of the above.
>
> The attached patch silences the warnings, because we *know* we're overwriting
> the default initializer. That leaves bpf/core.c with only 6 other warnings,
> which become more visible in comparison.
>
> Signed-off-by: Valdis Kletnieks <valdis.kletnieks@vt.edu>

Thanks! Please include bpf-next in [PATCH] prefix in the future. I've
also CC'ed bpf@vger.kernel.org list.

Acked-by: Andrii Nakryiko <andriin@fb.com>

>
> diff --git a/kernel/bpf/Makefile b/kernel/bpf/Makefile
> index 4c2fa3ac56f6..2606665f2cb5 100644
> --- a/kernel/bpf/Makefile
> +++ b/kernel/bpf/Makefile
> @@ -21,3 +21,4 @@ obj-$(CONFIG_CGROUP_BPF) += cgroup.o
>  ifeq ($(CONFIG_INET),y)
>  obj-$(CONFIG_BPF_SYSCALL) += reuseport_array.o
>  endif
> +CFLAGS_core.o          += $(call cc-disable-warning, override-init)
>
>

Re: [PATCH] bpf/core.c - silence warning messages

[Daniel Borkmann]

On 06/07/2019 04:39 AM, Valdis Klētnieks wrote:
> Compiling kernel/bpf/core.c with W=1 causes a flood of warnings:
> 
> kernel/bpf/core.c:1198:65: warning: initialized field overwritten [-Woverride-init]
>  1198 | #define BPF_INSN_3_TBL(x, y, z) [BPF_##x | BPF_##y | BPF_##z] = true
>       |                                                                 ^~~~
> kernel/bpf/core.c:1087:2: note: in expansion of macro 'BPF_INSN_3_TBL'
>  1087 |  INSN_3(ALU, ADD,  X),   \
>       |  ^~~~~~
> kernel/bpf/core.c:1202:3: note: in expansion of macro 'BPF_INSN_MAP'
>  1202 |   BPF_INSN_MAP(BPF_INSN_2_TBL, BPF_INSN_3_TBL),
>       |   ^~~~~~~~~~~~
> kernel/bpf/core.c:1198:65: note: (near initialization for 'public_insntable[12]')
>  1198 | #define BPF_INSN_3_TBL(x, y, z) [BPF_##x | BPF_##y | BPF_##z] = true
>       |                                                                 ^~~~
> kernel/bpf/core.c:1087:2: note: in expansion of macro 'BPF_INSN_3_TBL'
>  1087 |  INSN_3(ALU, ADD,  X),   \
>       |  ^~~~~~
> kernel/bpf/core.c:1202:3: note: in expansion of macro 'BPF_INSN_MAP'
>  1202 |   BPF_INSN_MAP(BPF_INSN_2_TBL, BPF_INSN_3_TBL),
>       |   ^~~~~~~~~~~~
> 
> 98 copies of the above.
> 
> The attached patch silences the warnings, because we *know* we're overwriting
> the default initializer. That leaves bpf/core.c with only 6 other warnings,
> which become more visible in comparison.
> 
> Signed-off-by: Valdis Kletnieks <valdis.kletnieks@vt.edu>

Makes sense, applied!

Re: [PATCH] bpf/core.c - silence warning messages

[Song Liu]

On Mon, Jan 28, 2019 at 3:35 PM <valdis.kletnieks@vt.edu> wrote:
>
> On Mon, 28 Jan 2019 09:18:45 -0800, Song Liu said:
> > On Sun, Jan 27, 2019 at 8:43 PM <valdis.kletnieks@vt.edu> wrote:
>
> > > The attached patch silences the warnings, because we *know* we're overwriting
> > > the default initializer. That leaves bpf/core.c with only 6 other warnings,
> > > which become more visible in comparison.
> >
> > My concern is that this will also mute the warning for other parts of
> > bpf/core.c.
>
> I checked and there weren't any warnings for other parts of the file.  Also, this message
> doesn't even happen unless you build with W=1, which apparently happens so rarely
> that nobody else has submitted a patch.
>
> Is there a high likelihood that another overwrite of an initializer is going to
> be included in the source?
>
> > Maybe we should move bpf_opcode_in_insntable() to a separate file, and mute
> > warning for that file?
>
> Seems to be overkill - the intent of this patch was mostly to make the *other*
> warnings issued with W=1 more noticable.

Yeah, I also felt this might be overkill while asking initially.

Acked-by: Song Liu <songliubraving@fb.com>

Re: [PATCH] bpf/core.c - silence warning messages

[Daniel Borkmann]

On 01/29/2019 12:48 AM, valdis.kletnieks@vt.edu wrote:
> On Tue, 29 Jan 2019 00:22:26 +0100, Daniel Borkmann said:
>> I think moving in separate file would be overkill, imho. However, lets get
>> the kdoc and prototype warning fixed.
> 
> I have a bunch of spare time at the moment, so the kdoc and prototype
> warnings are on my to-do list.

Great, thanks!

Re: [PATCH] bpf/core.c - silence warning messages

[valdis.kletnieks]

On Tue, 29 Jan 2019 00:22:26 +0100, Daniel Borkmann said:
> I think moving in separate file would be overkill, imho. However, lets get
> the kdoc and prototype warning fixed.

I have a bunch of spare time at the moment, so the kdoc and prototype
warnings are on my to-do list.

Re: [PATCH] bpf/core.c - silence warning messages

[valdis.kletnieks]

On Mon, 28 Jan 2019 09:18:45 -0800, Song Liu said:
> On Sun, Jan 27, 2019 at 8:43 PM <valdis.kletnieks@vt.edu> wrote:

> > The attached patch silences the warnings, because we *know* we're overwriting
> > the default initializer. That leaves bpf/core.c with only 6 other warnings,
> > which become more visible in comparison.
>
> My concern is that this will also mute the warning for other parts of
> bpf/core.c.

I checked and there weren't any warnings for other parts of the file.  Also, this message
doesn't even happen unless you build with W=1, which apparently happens so rarely
that nobody else has submitted a patch.

Is there a high likelihood that another overwrite of an initializer is going to
be included in the source?

> Maybe we should move bpf_opcode_in_insntable() to a separate file, and mute
> warning for that file?

Seems to be overkill - the intent of this patch was mostly to make the *other*
warnings issued with W=1 more noticable.

Re: [PATCH] bpf/core.c - silence warning messages

[Daniel Borkmann]

On 01/28/2019 06:18 PM, Song Liu wrote:
> On Sun, Jan 27, 2019 at 8:43 PM <valdis.kletnieks@vt.edu> wrote:
>>
>> Compiling kernel/bpf/core.c with W=1 causes a flood of warnings:
>>
>> kernel/bpf/core.c:1198:65: warning: initialized field overwritten [-Woverride-init]
>>  1198 | #define BPF_INSN_3_TBL(x, y, z) [BPF_##x | BPF_##y | BPF_##z] = true
>>       |                                                                 ^~~~
>> kernel/bpf/core.c:1087:2: note: in expansion of macro 'BPF_INSN_3_TBL'
>>  1087 |  INSN_3(ALU, ADD,  X),   \
>>       |  ^~~~~~
>> kernel/bpf/core.c:1202:3: note: in expansion of macro 'BPF_INSN_MAP'
>>  1202 |   BPF_INSN_MAP(BPF_INSN_2_TBL, BPF_INSN_3_TBL),
>>       |   ^~~~~~~~~~~~
>> kernel/bpf/core.c:1198:65: note: (near initialization for 'public_insntable[12]')
>>  1198 | #define BPF_INSN_3_TBL(x, y, z) [BPF_##x | BPF_##y | BPF_##z] = true
>>       |                                                                 ^~~~
>> kernel/bpf/core.c:1087:2: note: in expansion of macro 'BPF_INSN_3_TBL'
>>  1087 |  INSN_3(ALU, ADD,  X),   \
>>       |  ^~~~~~
>> kernel/bpf/core.c:1202:3: note: in expansion of macro 'BPF_INSN_MAP'
>>  1202 |   BPF_INSN_MAP(BPF_INSN_2_TBL, BPF_INSN_3_TBL),
>>       |   ^~~~~~~~~~~~
>>
>> 98 copies of the above.
>>
>> The attached patch silences the warnings, because we *know* we're overwriting
>> the default initializer. That leaves bpf/core.c with only 6 other warnings,
>> which become more visible in comparison.
> 
> My concern is that this will also mute the warning for other parts of
> bpf/core.c.

Agree, valid concern.

> Maybe we should move bpf_opcode_in_insntable() to a separate file, and mute
> warning for that file?

I think moving in separate file would be overkill, imho. However, lets get
the kdoc and prototype warning fixed.

Thanks,
Daniel

Re: [PATCH] bpf/core.c - silence warning messages

[Song Liu]

On Sun, Jan 27, 2019 at 8:43 PM <valdis.kletnieks@vt.edu> wrote:
>
> Compiling kernel/bpf/core.c with W=1 causes a flood of warnings:
>
> kernel/bpf/core.c:1198:65: warning: initialized field overwritten [-Woverride-init]
>  1198 | #define BPF_INSN_3_TBL(x, y, z) [BPF_##x | BPF_##y | BPF_##z] = true
>       |                                                                 ^~~~
> kernel/bpf/core.c:1087:2: note: in expansion of macro 'BPF_INSN_3_TBL'
>  1087 |  INSN_3(ALU, ADD,  X),   \
>       |  ^~~~~~
> kernel/bpf/core.c:1202:3: note: in expansion of macro 'BPF_INSN_MAP'
>  1202 |   BPF_INSN_MAP(BPF_INSN_2_TBL, BPF_INSN_3_TBL),
>       |   ^~~~~~~~~~~~
> kernel/bpf/core.c:1198:65: note: (near initialization for 'public_insntable[12]')
>  1198 | #define BPF_INSN_3_TBL(x, y, z) [BPF_##x | BPF_##y | BPF_##z] = true
>       |                                                                 ^~~~
> kernel/bpf/core.c:1087:2: note: in expansion of macro 'BPF_INSN_3_TBL'
>  1087 |  INSN_3(ALU, ADD,  X),   \
>       |  ^~~~~~
> kernel/bpf/core.c:1202:3: note: in expansion of macro 'BPF_INSN_MAP'
>  1202 |   BPF_INSN_MAP(BPF_INSN_2_TBL, BPF_INSN_3_TBL),
>       |   ^~~~~~~~~~~~
>
> 98 copies of the above.
>
> The attached patch silences the warnings, because we *know* we're overwriting
> the default initializer. That leaves bpf/core.c with only 6 other warnings,
> which become more visible in comparison.

My concern is that this will also mute the warning for other parts of
bpf/core.c.

Maybe we should move bpf_opcode_in_insntable() to a separate file, and mute
warning for that file?

Daniel and Alexei, what do you think?

Thanks,
Song


>
> Signed-off-by: Valdis Kletnieks <valdis.kletnieks@vt.edu>
>
> diff --git a/kernel/bpf/Makefile b/kernel/bpf/Makefile
> index 4c2fa3ac56f6..2606665f2cb5 100644
> --- a/kernel/bpf/Makefile
> +++ b/kernel/bpf/Makefile
> @@ -21,3 +21,4 @@ obj-$(CONFIG_CGROUP_BPF) += cgroup.o
>  ifeq ($(CONFIG_INET),y)
>  obj-$(CONFIG_BPF_SYSCALL) += reuseport_array.o
>  endif
> +CFLAGS_core.o          += $(call cc-disable-warning, override-init)
>

[PATCH] bpf/core.c - silence warning messages

[valdis.kletnieks]

Compiling kernel/bpf/core.c with W=1 causes a flood of warnings:

kernel/bpf/core.c:1198:65: warning: initialized field overwritten [-Woverride-init]
 1198 | #define BPF_INSN_3_TBL(x, y, z) [BPF_##x | BPF_##y | BPF_##z] = true
      |                                                                 ^~~~
kernel/bpf/core.c:1087:2: note: in expansion of macro 'BPF_INSN_3_TBL'
 1087 |  INSN_3(ALU, ADD,  X),   \
      |  ^~~~~~
kernel/bpf/core.c:1202:3: note: in expansion of macro 'BPF_INSN_MAP'
 1202 |   BPF_INSN_MAP(BPF_INSN_2_TBL, BPF_INSN_3_TBL),
      |   ^~~~~~~~~~~~
kernel/bpf/core.c:1198:65: note: (near initialization for 'public_insntable[12]')
 1198 | #define BPF_INSN_3_TBL(x, y, z) [BPF_##x | BPF_##y | BPF_##z] = true
      |                                                                 ^~~~
kernel/bpf/core.c:1087:2: note: in expansion of macro 'BPF_INSN_3_TBL'
 1087 |  INSN_3(ALU, ADD,  X),   \
      |  ^~~~~~
kernel/bpf/core.c:1202:3: note: in expansion of macro 'BPF_INSN_MAP'
 1202 |   BPF_INSN_MAP(BPF_INSN_2_TBL, BPF_INSN_3_TBL),
      |   ^~~~~~~~~~~~

98 copies of the above.

The attached patch silences the warnings, because we *know* we're overwriting
the default initializer. That leaves bpf/core.c with only 6 other warnings,
which become more visible in comparison.

Signed-off-by: Valdis Kletnieks <valdis.kletnieks@vt.edu>

diff --git a/kernel/bpf/Makefile b/kernel/bpf/Makefile
index 4c2fa3ac56f6..2606665f2cb5 100644
--- a/kernel/bpf/Makefile
+++ b/kernel/bpf/Makefile
@@ -21,3 +21,4 @@ obj-$(CONFIG_CGROUP_BPF) += cgroup.o
 ifeq ($(CONFIG_INET),y)
 obj-$(CONFIG_BPF_SYSCALL) += reuseport_array.o
 endif
+CFLAGS_core.o          += $(call cc-disable-warning, override-init)