* [PATCH bpf-next V2 0/2] bpf: avoid `attribute ignored' warnings in GCC
@ 2024-05-07 7:42 Jose E. Marchesi
2024-05-07 7:42 ` [PATCH bpf-next V2 1/2] bpf: avoid __hidden__ attribute in static object Jose E. Marchesi
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: Jose E. Marchesi @ 2024-05-07 7:42 UTC (permalink / raw
To: bpf
These two patches avoid warnings (turned into errors) when building
the BPF selftests with GCC.
[Changes from V1:
- As requested by reviewer, an additional patch has been added in
order to remove __hidden from the `private' macro in
cpumask_common.h.
- Typo bening -> benign fixed in the commit message of the second
patch.]
Jose E. Marchesi (2):
bpf: avoid __hidden__ attribute in static object
bpf: disable some `attribute ignored' warnings in GCC
tools/testing/selftests/bpf/Makefile | 2 +-
tools/testing/selftests/bpf/progs/cpumask_common.h | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
--
2.30.2
^ permalink raw reply [flat|nested] 4+ messages in thread
* [PATCH bpf-next V2 1/2] bpf: avoid __hidden__ attribute in static object
2024-05-07 7:42 [PATCH bpf-next V2 0/2] bpf: avoid `attribute ignored' warnings in GCC Jose E. Marchesi
@ 2024-05-07 7:42 ` Jose E. Marchesi
2024-05-07 7:42 ` [PATCH bpf-next V2 2/2] bpf: disable some `attribute ignored' warnings in GCC Jose E. Marchesi
2024-05-07 21:40 ` [PATCH bpf-next V2 0/2] bpf: avoid " patchwork-bot+netdevbpf
2 siblings, 0 replies; 4+ messages in thread
From: Jose E. Marchesi @ 2024-05-07 7:42 UTC (permalink / raw
To: bpf; +Cc: Jose E . Marchesi, david.faust, cupertino.miranda, Yonghong Song
An object defined as `static' defaults to hidden visibility. If
additionally the visibility(__weak__) compiler attribute is applied to
the declaration of the object, GCC warns that the attribute gets
ignored.
This patch removes the only instance of this problem among the BPF
selftests.
Tested in bpf-next master.
Signed-off-by: Jose E. Marchesi <jose.marchesi@oracle.com>
Cc: david.faust@oracle.com
Cc: cupertino.miranda@oracle.com
Cc: Yonghong Song <yonghong.song@linux.dev>
Acked-by: Yonghong Song <yonghong.song@linux.dev>
---
tools/testing/selftests/bpf/progs/cpumask_common.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/tools/testing/selftests/bpf/progs/cpumask_common.h b/tools/testing/selftests/bpf/progs/cpumask_common.h
index c705d8112a35..b979e91f55f0 100644
--- a/tools/testing/selftests/bpf/progs/cpumask_common.h
+++ b/tools/testing/selftests/bpf/progs/cpumask_common.h
@@ -9,7 +9,7 @@
int err;
-#define private(name) SEC(".bss." #name) __hidden __attribute__((aligned(8)))
+#define private(name) SEC(".bss." #name) __attribute__((aligned(8)))
private(MASK) static struct bpf_cpumask __kptr * global_mask;
struct __cpumask_map_value {
--
2.30.2
^ permalink raw reply related [flat|nested] 4+ messages in thread
* [PATCH bpf-next V2 2/2] bpf: disable some `attribute ignored' warnings in GCC
2024-05-07 7:42 [PATCH bpf-next V2 0/2] bpf: avoid `attribute ignored' warnings in GCC Jose E. Marchesi
2024-05-07 7:42 ` [PATCH bpf-next V2 1/2] bpf: avoid __hidden__ attribute in static object Jose E. Marchesi
@ 2024-05-07 7:42 ` Jose E. Marchesi
2024-05-07 21:40 ` [PATCH bpf-next V2 0/2] bpf: avoid " patchwork-bot+netdevbpf
2 siblings, 0 replies; 4+ messages in thread
From: Jose E. Marchesi @ 2024-05-07 7:42 UTC (permalink / raw
To: bpf
Cc: Jose E . Marchesi, david.faust, cupertino.miranda, Yonghong Song,
Eduard Zingerman
This patch modifies selftests/bpf/Makefile to pass -Wno-attributes to
GCC. This is because of the following attributes which are ignored:
- btf_decl_tag
- btf_type_tag
There are many of these. At the moment none of these are
recognized/handled by gcc-bpf.
We are aware that btf_decl_tag is necessary for some of the
selftest harness to communicate test failure/success. Support for
it is in progress in GCC upstream:
https://gcc.gnu.org/pipermail/gcc-patches/2024-May/650482.html
However, the GCC master branch is not yet open, so the series
above (currently under review upstream) wont be able to make it
there until 14.1 gets released, probably mid next week.
As for btf_type_tag, more extensive work will be needed in GCC
upstream to support it in both BTF and DWARF. We have a WIP big
patch for that, but that is not needed to compile/build the
selftests.
- used
There are SEC macros defined in the selftests as:
#define SEC(N) __attribute__((section(N),used))
The SEC macro is used for both functions and global variables.
According to the GCC documentation `used' attribute is really only
meaningful for functions, and it warns when the attribute is used
for other global objects, like for example ctl_array in
test_xdp_noinline.c.
Ignoring this is benign.
- align_value
In progs/test_cls_redirect.c:127 there is:
typedef uint8_t *net_ptr __attribute__((align_value(8)));
GCC warns that it is ignoring this attribute, because it is not
implemented by GCC.
I think ignoring this attribute in GCC is benign, because according
to the clang documentation [1] its purpose seems to be merely
declarative and doesn't seem to translate into extra checks at
run-time, only to perhaps better optimized code ("runtime behavior
is undefined if the pointed memory object is not aligned to the
specified alignment").
[1] https://clang.llvm.org/docs/AttributeReference.html#align-value
Tested in bpf-next master.
Signed-off-by: Jose E. Marchesi <jose.marchesi@oracle.com>
Cc: david.faust@oracle.com
Cc: cupertino.miranda@oracle.com
Cc: Yonghong Song <yonghong.song@linux.dev>
Cc: Eduard Zingerman <eddyz87@gmail.com>
Acked-by: Yonghong Song <yonghong.song@linux.dev>
---
tools/testing/selftests/bpf/Makefile | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index ba28d42b74db..5d9c906bc3cb 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -431,7 +431,7 @@ endef
# Build BPF object using GCC
define GCC_BPF_BUILD_RULE
$(call msg,GCC-BPF,$(TRUNNER_BINARY),$2)
- $(Q)$(BPF_GCC) $3 -O2 -c $1 -o $2
+ $(Q)$(BPF_GCC) $3 -Wno-attributes -O2 -c $1 -o $2
endef
SKEL_BLACKLIST := btf__% test_pinning_invalid.c test_sk_assign.c
--
2.30.2
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH bpf-next V2 0/2] bpf: avoid `attribute ignored' warnings in GCC
2024-05-07 7:42 [PATCH bpf-next V2 0/2] bpf: avoid `attribute ignored' warnings in GCC Jose E. Marchesi
2024-05-07 7:42 ` [PATCH bpf-next V2 1/2] bpf: avoid __hidden__ attribute in static object Jose E. Marchesi
2024-05-07 7:42 ` [PATCH bpf-next V2 2/2] bpf: disable some `attribute ignored' warnings in GCC Jose E. Marchesi
@ 2024-05-07 21:40 ` patchwork-bot+netdevbpf
2 siblings, 0 replies; 4+ messages in thread
From: patchwork-bot+netdevbpf @ 2024-05-07 21:40 UTC (permalink / raw
To: Jose E. Marchesi; +Cc: bpf
Hello:
This series was applied to bpf/bpf-next.git (master)
by Andrii Nakryiko <andrii@kernel.org>:
On Tue, 7 May 2024 09:42:25 +0200 you wrote:
> These two patches avoid warnings (turned into errors) when building
> the BPF selftests with GCC.
>
> [Changes from V1:
> - As requested by reviewer, an additional patch has been added in
> order to remove __hidden from the `private' macro in
> cpumask_common.h.
> - Typo bening -> benign fixed in the commit message of the second
> patch.]
>
> [...]
Here is the summary with links:
- [bpf-next,V2,1/2] bpf: avoid __hidden__ attribute in static object
https://git.kernel.org/bpf/bpf-next/c/2ce987e16502
- [bpf-next,V2,2/2] bpf: disable some `attribute ignored' warnings in GCC
https://git.kernel.org/bpf/bpf-next/c/b0fbdf759da0
You are awesome, thank you!
--
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html
^ permalink raw reply [flat|nested] 4+ messages in thread
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2024-05-07 7:42 [PATCH bpf-next V2 0/2] bpf: avoid `attribute ignored' warnings in GCC Jose E. Marchesi
2024-05-07 7:42 ` [PATCH bpf-next V2 1/2] bpf: avoid __hidden__ attribute in static object Jose E. Marchesi
2024-05-07 7:42 ` [PATCH bpf-next V2 2/2] bpf: disable some `attribute ignored' warnings in GCC Jose E. Marchesi
2024-05-07 21:40 ` [PATCH bpf-next V2 0/2] bpf: avoid " patchwork-bot+netdevbpf
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