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Re: [PATCH] binfmt_misc: pass binfmt_misc P flag to the interpreter
- From: Florian Weimer <fw at deneb dot enyo dot de>
- To: YunQiang Su <syq at debian dot org>
- Cc: Laurent Vivier <laurent at vivier dot eu>, torvalds at linux-foundation dot org, Greg KH <gregkh at linuxfoundation dot org>, akpm at linux-foundation dot org, Al Viro <viro at zeniv dot linux dot org dot uk>, James Bottomley <James dot Bottomley at hansenpartnership dot com>, linux-kernel at vger dot kernel dot org, linux-fsdevel at vger dot kernel dot org, linux-arch at vger dot kernel dot org, linux-api at vger dot kernel dot org, libc-alpha at sourceware dot org
- Date: Fri, 06 Mar 2020 13:07:33 +0100
- Subject: Re: [PATCH] binfmt_misc: pass binfmt_misc P flag to the interpreter
- References: <20200306080905.173466-1-syq@debian.org> <87r1y53npd.fsf@mid.deneb.enyo.de> <8441f497-61eb-5c14-bf1e-c90a464105a7@vivier.eu> <87mu8t3mlw.fsf@mid.deneb.enyo.de> <40da389d-4e74-2644-2e7c-04d988fcc26f@vivier.eu> <CAKcpw6WEO5Rmsv+WFkOMrkH+0jwtFKKy7b2n3U9xgv-xGC0UUQ@mail.gmail.com> <87v9nhzp6w.fsf@mid.deneb.enyo.de> <CAKcpw6VF1N2gTVXeWLU4aVOuARf5oN6yPg9O=RCzgkMrjXmxYQ@mail.gmail.com>
* YunQiang Su:
> Florian Weimer <fw@deneb.enyo.de> 于2020年3月6日周五 下午7:42写道：
>>
>> * YunQiang Su:
>>
>> > AT_* only has 32 slot and now. I was afraid that maybe we shouldn't take one.
>> > /* AT_* values 18 through 22 are reserved */
>> > 27,28,29,30 are not used now.
>> > Which should we use?
>>
>> Where does this limit of 32 tags come from? I don't see it from a
>> userspace perspective.
>
> Sorry it is my mistake: In linux/auxvec.h, I saw
>
> #define AT_RANDOM 25 /* address of 16 random bytes */
> #define AT_HWCAP2 26 /* extension of AT_HWCAP */
>
> #define AT_EXECFN 31 /* filename of program */
>
> The number jump to 31 from 26.
>
> It is my fault: in x86_64-linux-gnu/bits/auxv.h, the max number is 47 now.
So AT_* tags aren't a scarce resource after all?