From: Adhemerval Zanella <adhemerval.zanella@linaro.org>
To: Andreas Schwab <schwab@linux-m68k.org>
Cc: Michal Nazarewicz <mina86@mina86.com>, libc-alpha@sourceware.org
Subject: Re: [PATCH] linux: sysconf: limit _SC_MAX_ARG to 6 MiB [BZ #25305]
Date: Tue, 13 Apr 2021 11:45:41 -0300 [thread overview]
Message-ID: <c036618a-d8a8-b439-82e6-86cfecf5c09a@linaro.org> (raw)
In-Reply-To: <87eefedz76.fsf@igel.home>
On 13/04/2021 11:41, Andreas Schwab wrote:
> On Apr 13 2021, Adhemerval Zanella wrote:
>
>> On 13/04/2021 09:13, Andreas Schwab wrote:
>>> On Apr 12 2021, Michal Nazarewicz wrote:
>>>
>>>>> On 07/04/2021 12:10, Michal Nazarewicz wrote:
>>>>>> Since Linux 4.13, kernel limits the maximum command line arguments
>>>>>> length to 6 MiB.¹ Normally the limit is still quarter of the maximum
>>>>>> stack size but if that limit exceeds 6 MiB it’s clamped down.
>>>>
>>>> On Mon, Apr 12 2021, Adhemerval Zanella wrote:
>>>>> Patch look good to me, thanks.
>>>>>
>>>>> Reviewed=by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
>>>>>
>>>>>> ---
>>>>>> sysdeps/unix/sysv/linux/sysconf.c | 5 ++++-
>>>>>> 1 file changed, 4 insertions(+), 1 deletion(-)
>>>>>>
>>>>>> diff --git a/sysdeps/unix/sysv/linux/sysconf.c b/sysdeps/unix/sysv/linux/sysconf.c
>>>>>> index 366fcef01e..bd711795c7 100644
>>>>>> --- a/sysdeps/unix/sysv/linux/sysconf.c
>>>>>> +++ b/sysdeps/unix/sysv/linux/sysconf.c
>>>>>> @@ -55,7 +55,10 @@ __sysconf (int name)
>>>>>> struct rlimit rlimit;
>>>>>> /* Use getrlimit to get the stack limit. */
>>>>>> if (__getrlimit (RLIMIT_STACK, &rlimit) == 0)
>>>>>> - return MAX (legacy_ARG_MAX, rlimit.rlim_cur / 4);
>>>>>> + {
>>>>>> + const long int limit = MAX (legacy_ARG_MAX, rlimit.rlim_cur / 4);
>>>>>> + return MIN (limit, 6 << 10 << 10);
>>>>>
>>>>> I think it a bit easier to read with the value expanded (6291456).
>>>>
>>>> I’d rather go with ‘6 * 1024 * 1024’ if shifts aren’t readable.
>>>
>>> In addition, I'd give it a symbolic name with a comment.
>>
>> What about:
>>
>> diff --git a/sysdeps/unix/sysv/linux/sysconf.c b/sysdeps/unix/sysv/linux/sysconf.c
>> index 366fcef01e..aceedfa87c 100644
>> --- a/sysdeps/unix/sysv/linux/sysconf.c
>> +++ b/sysdeps/unix/sysv/linux/sysconf.c
>> @@ -33,6 +33,9 @@
>> actual value varies based on the stack size. */
>> #define legacy_ARG_MAX 131072
>>
>> +/* Newer kernels (4.13) limit the maximum command line arguments lengths to
>> + 6MiB. */
>> +#define maximum_ARG_MAX 6291456
>
> I'd still use 6 * 1024 * 1024 here, small numbers are much easier to
> grok.
Ack.
next prev parent reply other threads:[~2021-04-13 14:45 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-07 15:10 Michal Nazarewicz
2021-04-07 18:36 ` Adhemerval Zanella
2021-04-07 18:41 ` Florian Weimer
2021-04-07 18:52 ` Adhemerval Zanella
2021-04-07 19:04 ` Florian Weimer
2021-04-07 19:34 ` Adhemerval Zanella
2021-04-07 19:36 ` Florian Weimer
2021-04-08 1:49 ` Michal Nazarewicz
2021-04-12 20:59 ` Adhemerval Zanella
2021-04-12 21:31 ` Michal Nazarewicz
2021-04-13 11:53 ` Adhemerval Zanella
2021-04-13 12:13 ` Andreas Schwab
2021-04-13 13:36 ` Adhemerval Zanella
2021-04-13 14:41 ` Andreas Schwab
2021-04-13 14:45 ` Adhemerval Zanella [this message]
2021-04-13 19:57 ` Michal Nazarewicz
2021-04-13 20:47 ` Adhemerval Zanella
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