linux-kernel - Re: [PATCH bpf 1/2] samples/bpf: Set flag __SANE_USERSPACE_TYPES_

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Message-ID: <f077bcae-97be-fc7f-c3fa-c6026bfe25d2@loongson.cn>
Date:   Mon, 18 Jan 2021 11:22:20 +0800
From:   Tiezhu Yang <yangtiezhu@...ngson.cn>
To:     Yonghong Song <yhs@...com>,
        Luc Van Oostenryck <luc.vanoostenryck@...il.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Nathan Chancellor <natechancellor@...il.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     linux-sparse@...r.kernel.org, netdev@...r.kernel.org,
        bpf@...r.kernel.org, clang-built-linux@...glegroups.com,
        linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org,
        Xuefeng Li <lixuefeng@...ngson.cn>
Subject: Re: [PATCH bpf 1/2] samples/bpf: Set flag __SANE_USERSPACE_TYPES__
 for MIPS to fix build warnings

On 01/14/2021 01:12 AM, Yonghong Song wrote:
>
>
> On 1/13/21 2:57 AM, Tiezhu Yang wrote:
>> MIPS needs __SANE_USERSPACE_TYPES__ before <linux/types.h> to select
>> 'int-ll64.h' in arch/mips/include/uapi/asm/types.h and avoid compile
>> warnings when printing __u64 with %llu, %llx or %lld.
>
> could you mention which command produces the following warning?

make M=samples/bpf

>
>>
>>      printf("0x%02x : %llu\n", key, value);
>>                       ~~~^          ~~~~~
>>                       %lu
>>     printf("%s/%llx;", sym->name, addr);
>>                ~~~^               ~~~~
>>                %lx
>>    printf(";%s %lld\n", key->waker, count);
>>                ~~~^                 ~~~~~
>>                %ld
>>
>> Signed-off-by: Tiezhu Yang <yangtiezhu@...ngson.cn>
>> ---
>>   samples/bpf/Makefile        | 4 ++++
>>   tools/include/linux/types.h | 3 +++
>>   2 files changed, 7 insertions(+)
>>
>> diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
>> index 26fc96c..27de306 100644
>> --- a/samples/bpf/Makefile
>> +++ b/samples/bpf/Makefile
>> @@ -183,6 +183,10 @@ BPF_EXTRA_CFLAGS := $(ARM_ARCH_SELECTOR)
>>   TPROGS_CFLAGS += $(ARM_ARCH_SELECTOR)
>>   endif
>>   +ifeq ($(ARCH), mips)
>> +TPROGS_CFLAGS += -D__SANE_USERSPACE_TYPES__
>> +endif
>> +
>
> This change looks okay based on description in
> arch/mips/include/uapi/asm/types.h
>
> '''
> /*
>  * We don't use int-l64.h for the kernel anymore but still use it for
>  * userspace to avoid code changes.
>  *
>  * However, some user programs (e.g. perf) may not want this. They can
>  * flag __SANE_USERSPACE_TYPES__ to get int-ll64.h here.
>  */
> '''
>
>>   TPROGS_CFLAGS += -Wall -O2
>>   TPROGS_CFLAGS += -Wmissing-prototypes
>>   TPROGS_CFLAGS += -Wstrict-prototypes
>> diff --git a/tools/include/linux/types.h b/tools/include/linux/types.h
>> index 154eb4e..e9c5a21 100644
>> --- a/tools/include/linux/types.h
>> +++ b/tools/include/linux/types.h
>> @@ -6,7 +6,10 @@
>>   #include <stddef.h>
>>   #include <stdint.h>
>>   +#ifndef __SANE_USERSPACE_TYPES__
>>   #define __SANE_USERSPACE_TYPES__    /* For PPC64, to get LL64 types */
>> +#endif
>
> What problem this patch fixed?

If add "TPROGS_CFLAGS += -D__SANE_USERSPACE_TYPES__" in
samples/bpf/Makefile, it appears the following error:

Auto-detecting system features:
...                        libelf: [ on  ]
...                          zlib: [ on  ]
...                           bpf: [ OFF ]

BPF API too old
make[3]: *** [Makefile:293: bpfdep] Error 1
make[2]: *** [Makefile:156: all] Error 2

With #ifndef __SANE_USERSPACE_TYPES__  in tools/include/linux/types.h,
the above error has gone.

> If this header is used, you can just
> change comment from "PPC64" to "PPC64/MIPS", right?

If include <linux/types.h> in the source files which have compile warnings
when printing __u64 with %llu, %llx or %lld, it has no effect due to 
actually
it includes usr/include/linux/types.h instead of 
tools/include/linux/types.h,
this is because the include-directories in samples/bpf/Makefile are searched
in the order, -I./usr/include is in the front of -I./tools/include.

So I think define __SANE_USERSPACE_TYPES__ for MIPS in samples/bpf/Makefile
is proper, at the same time, add #ifndef __SANE_USERSPACE_TYPES__ in
tools/include/linux/types.h can avoid build error and have no side effect.

I will send v2 later with mention in the commit message that this is
mips related.

Thanks,
Tiezhu

>
>> +
>>   #include <asm/types.h>
>>   #include <asm/posix_types.h>
>>