linux-kernel - Re: [PATCH 1/5] perf tools: Add get_unaligned

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Date:   Thu, 26 Oct 2023 19:09:26 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Jiri Olsa <jolsa@...nel.org>, Namhyung Kim <namhyung@...nel.org>,
        Ian Rogers <irogers@...gle.com>, linux-kernel@...r.kernel.org,
        linux-perf-users@...r.kernel.org
Subject: Re: [PATCH 1/5] perf tools: Add get_unaligned_leNN()

On 26/10/23 16:44, Arnaldo Carvalho de Melo wrote:
> Em Thu, Oct 05, 2023 at 04:38:05PM -0300, Arnaldo Carvalho de Melo escreveu:
>> Em Thu, Oct 05, 2023 at 10:04:47PM +0300, Adrian Hunter escreveu:
>>> Add get_unaligned_le16(), get_unaligned_le32 and get_unaligned_le64, same
>>> as include/asm-generic/unaligned.h.
>>>
>>> Use diagnostic pragmas to ignore -Wpacked used by perf build.
>>
>> Can we get the tools copy of include/asm-generic/unaligned.h closer and
>> have it in check-headers.sh?
> 
> And this is not building when cross building to mips, mips64 and mipsel
> on debian:experimental:
> 
> In file included from util/intel-pt-decoder/intel-pt-pkt-decoder.c:10:
> /git/perf-6.6.0-rc1/tools/include/asm-generic/unaligned.h: In function 'get_unaligned_le16':
> /git/perf-6.6.0-rc1/tools/include/asm-generic/unaligned.h:13:29: error: packed attribute causes inefficient alignment for 'x' [-Werror=attributes]

So I guess another diagnostic pragma is needed, perhaps the following works?

#pragma GCC diagnostic ignored "-Wattributes"


>    13 |         const struct { type x; } __packed *__pptr = (typeof(__pptr))(ptr);      \
>       |                             ^
> /git/perf-6.6.0-rc1/tools/include/asm-generic/unaligned.h:27:28: note: in expansion of macro '__get_unaligned_t'
>    27 |         return le16_to_cpu(__get_unaligned_t(__le16, p));
>       |                            ^~~~~~~~~~~~~~~~~
> /git/perf-6.6.0-rc1/tools/include/asm-generic/unaligned.h: In function 'get_unaligned_le32':
> /git/perf-6.6.0-rc1/tools/include/asm-generic/unaligned.h:13:29: error: packed attribute causes inefficient alignment for 'x' [-Werror=attributes]
>    13 |         const struct { type x; } __packed *__pptr = (typeof(__pptr))(ptr);      \
>       |                             ^
> /git/perf-6.6.0-rc1/tools/include/asm-generic/unaligned.h:32:28: note: in expansion of macro '__get_unaligned_t'
>    32 |         return le32_to_cpu(__get_unaligned_t(__le32, p));
>       |                            ^~~~~~~~~~~~~~~~~
> 
> 
> Ditto for some other distros when cross building on ubuntu:18.04
> 
>   MKDIR   /tmp/build/perf/util/perf-regs-arch/
> In file included from /usr/sparc64-linux-gnu/include/bits/byteswap.h:34:0,
>                  from /usr/sparc64-linux-gnu/include/endian.h:60,
>                  from util/intel-pt-decoder/intel-pt-pkt-decoder.c:9:
> /git/perf-6.6.0-rc1/tools/include/asm-generic/unaligned.h: In function 'get_unaligned_le16':
> /git/perf-6.6.0-rc1/tools/include/asm-generic/unaligned.h:13:22: error: packed attribute causes inefficient alignment for 'x' [-Werror=attributes]
>   const struct { type x; } __packed *__pptr = (typeof(__pptr))(ptr); \
>                       ^
> /git/perf-6.6.0-rc1/tools/include/asm-generic/unaligned.h:27:21: note: in expansion of macro '__get_unaligned_t'
>   return le16_to_cpu(__get_unaligned_t(__le16, p));
>                      ^~~~~~~~~~~~~~~~~
> 
>   37    14.17 ubuntu:18.04-x-arm            : FAIL gcc version 7.5.0 (Ubuntu/Linaro 7.5.0-3ubuntu1~18.04)
>   38    13.56 ubuntu:18.04-x-arm64          : FAIL gcc version 7.5.0 (Ubuntu/Linaro 7.5.0-3ubuntu1~18.04)
>   42    12.70 ubuntu:18.04-x-riscv64        : FAIL gcc version 7.5.0 (Ubuntu 7.5.0-3ubuntu1~18.04)
>   44    13.95 ubuntu:18.04-x-sh4            : FAIL gcc version 7.5.0 (Ubuntu 7.5.0-3ubuntu1~18.04)
>   45    13.08 ubuntu:18.04-x-sparc64        : FAIL gcc version 7.5.0 (Ubuntu 7.5.0-3ubuntu1~18.04)
>  
>> - Arnaldo
>>  
>>> Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
>>> ---
>>>  tools/include/asm-generic/unaligned.h | 20 ++++++++++++++++++++
>>>  1 file changed, 20 insertions(+)
>>>
>>> diff --git a/tools/include/asm-generic/unaligned.h b/tools/include/asm-generic/unaligned.h
>>> index 47387c607035..9140bb4e16c6 100644
>>> --- a/tools/include/asm-generic/unaligned.h
>>> +++ b/tools/include/asm-generic/unaligned.h
>>> @@ -6,6 +6,9 @@
>>>  #ifndef __TOOLS_LINUX_ASM_GENERIC_UNALIGNED_H
>>>  #define __TOOLS_LINUX_ASM_GENERIC_UNALIGNED_H
>>>  
>>> +#pragma GCC diagnostic push
>>> +#pragma GCC diagnostic ignored "-Wpacked"
>>> +
>>>  #define __get_unaligned_t(type, ptr) ({						\
>>>  	const struct { type x; } __packed *__pptr = (typeof(__pptr))(ptr);	\
>>>  	__pptr->x;								\
>>> @@ -19,5 +22,22 @@
>>>  #define get_unaligned(ptr)	__get_unaligned_t(typeof(*(ptr)), (ptr))
>>>  #define put_unaligned(val, ptr) __put_unaligned_t(typeof(*(ptr)), (val), (ptr))
>>>  
>>> +static inline u16 get_unaligned_le16(const void *p)
>>> +{
>>> +	return le16_to_cpu(__get_unaligned_t(__le16, p));
>>> +}
>>> +
>>> +static inline u32 get_unaligned_le32(const void *p)
>>> +{
>>> +	return le32_to_cpu(__get_unaligned_t(__le32, p));
>>> +}
>>> +
>>> +static inline u64 get_unaligned_le64(const void *p)
>>> +{
>>> +	return le64_to_cpu(__get_unaligned_t(__le64, p));
>>> +}
>>> +
>>> +#pragma GCC diagnostic pop
>>> +
>>>  #endif /* __TOOLS_LINUX_ASM_GENERIC_UNALIGNED_H */
>>>  
>>> -- 
>>> 2.34.1
>>>
>>
>> -- 
>>
>> - Arnaldo
>