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

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Date:   Mon, 18 Jan 2021 10:44:34 -0800
From:   Yonghong Song <yhs@...com>
To:     Tiezhu Yang <yangtiezhu@...ngson.cn>,
        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 1/17/21 7:22 PM, Tiezhu Yang wrote:
> 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.

It would be good if you can add the above information to the commit
message so people will know what the root cause of the issue.

If I understand correctly, if we could have include path
"tools/include" earlier than "usr/include", we might not have this 
issue. The problem is that "usr/include" is preferred first (uapi)
than "tools/include" (including kernel dev headers).

I am wondering whether we could avoid changes in 
tools/include/linux/types.h, e.g., by undef __SANE_USER_SPACE_TYPES 
right before include
path tools/include. But that sounds like a ugly hack and actually
the change in tools/include/linux/types.h does not hurt other
compilations.

So your current change looks good to me, but please have better
explanation of the problem and why for each change in the commit
message.

> 
> Thanks,
> Tiezhu
> 
>>
>>> +
>>>   #include <asm/types.h>
>>>   #include <asm/posix_types.h>
>>>
>