2019-06-07 03:08:53

by Valdis Klētnieks

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

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 <[email protected]>

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)

2019-06-11 05:51:08

by Andrii Nakryiko

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

On Thu, Jun 6, 2019 at 8:08 PM Valdis Klētnieks <[email protected]> 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 <[email protected]>

Thanks! Please include bpf-next in [PATCH] prefix in the future. I've
also CC'ed [email protected] list.

Acked-by: Andrii Nakryiko <[email protected]>

>
> 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)
>
>

2019-06-12 18:03:59

by Daniel Borkmann

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

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 <[email protected]>

Makes sense, applied!