linux-kernel - Re: [PATCH v4 1/1] x86, relocs: add printf attribute to die()

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Message-ID: <CAJfZ7=kzAgq57cvK+pj9G5yCmem3bnqFt_s0bo86ZYZbkNm_wA@mail.gmail.com>
Date:   Tue, 28 Mar 2017 23:06:24 +0200
From:   Nicolas Iooss <nicolas.iooss_linux@....org>
To:     Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>
Cc:     x86 <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 1/1] x86, relocs: add printf attribute to die()

On Tue, Mar 7, 2017 at 1:37 PM, Nicolas Iooss
<nicolas.iooss_linux@....org> wrote:
> On Tue, Mar 7, 2017 at 10:16 AM, Ingo Molnar <mingo@...nel.org> wrote:
>>
>> * Nicolas Iooss <nicolas.iooss_linux@....org> wrote:
>>
>>> Adding such an attribute helps to detect errors in the format string at
>>> build time. After doing this, the compiler complains about some issues:
>>>
>>>     arch/x86/tools/relocs.c:460:5: error: format specifies type 'int'
>>>     but the argument has type 'Elf64_Xword' (aka 'unsigned long')
>>>     [-Werror,-Wformat]
>>>                                     sec->shdr.sh_size);
>>>                                     ^~~~~~~~~~~~~~~~~
>>>     arch/x86/tools/relocs.c:464:5: error: format specifies type 'int'
>>>     but the argument has type 'Elf64_Off' (aka 'unsigned long')
>>>     [-Werror,-Wformat]
>>>                                     sec->shdr.sh_offset, strerror(errno));
>>>                                     ^~~~~~~~~~~~~~~~~~~
>>>
>>> When relocs.c is included by relocs_32.c, sec->shdr.sh_size and
>>> sec->shdr.sh_offset are 32-bit unsigned integers. When the file is
>>> included by relocs_64.c, these expressions are 64-bit unsigned integers.
>>>
>>> Add casts to unsigned long long, which length is always 64-bit, and use
>>> %llu to format sec->shdr.sh_size and sec->shdr.sh_offset in relocs.c.
>>>
>>> While at it, constify the format attribute of die().
>>>
>>> Signed-off-by: Nicolas Iooss <nicolas.iooss_linux@....org>
>>> ---
>>>  arch/x86/tools/relocs.c        | 31 +++++++++++++++++--------------
>>>  arch/x86/tools/relocs.h        |  3 ++-
>>>  arch/x86/tools/relocs_common.c |  2 +-
>>>  3 files changed, 20 insertions(+), 16 deletions(-)
>>>
>>> diff --git a/arch/x86/tools/relocs.c b/arch/x86/tools/relocs.c
>>> index 73eb7fd4aec4..3cc02065c677 100644
>>> --- a/arch/x86/tools/relocs.c
>>> +++ b/arch/x86/tools/relocs.c
>>> @@ -397,8 +397,8 @@ static void read_shdrs(FILE *fp)
>>>                   ehdr.e_shnum);
>>>       }
>>>       if (fseek(fp, ehdr.e_shoff, SEEK_SET) < 0) {
>>> -             die("Seek to %d failed: %s\n",
>>> -                     ehdr.e_shoff, strerror(errno));
>>> +             die("Seek to %llu failed: %s\n",
>>> +                     (unsigned long long)ehdr.e_shoff, strerror(errno));
>>
>> Isn't "(u64)" shorter to write?
>
> u64 does not seem to be defined in this file right now. Adding
> "#include <linux/types.h>" defines u64 and __u64 in the following way:
> - "typedef uint64_t u64;" from tools/include/linux/types.h
> - "typedef unsigned long long __u64;" from /usr/include/asm-generic/int-ll64.h
>
> uint64_t is unsigned long on x86-64 and gcc complains when using %llu
> on such a type, so using a cast to u64 forces using PRIu64 too.
>
> Nevertheless "(__u64)" is shorter than "(unsigned long long)" and
> seems to work fine in my quick tests because it is always unsigned
> long long (on both x86-32 and x86-64). Would you prefer to use this
> cast?

Hello,
After the question I had on the 4th revision of this patch, I have not
received any reply or comment for three weeks. What should I do in
order to get this merged?

Thanks,
Nicolas