From: Jeff Xu <jeffxu@chromium.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Pedro Falcato <pedro.falcato@gmail.com>,
Jeff Xu <jeffxu@google.com>, Matthew Wilcox <willy@infradead.org>,
akpm@linux-foundation.org, keescook@chromium.org,
sroettger@google.com, jorgelo@chromium.org, groeck@chromium.org,
linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org,
linux-mm@kvack.org, jannh@google.com, surenb@google.com,
alex.sierra@amd.com, apopple@nvidia.com,
aneesh.kumar@linux.ibm.com, axelrasmussen@google.com,
ben@decadent.org.uk, catalin.marinas@arm.com, david@redhat.com,
dwmw@amazon.co.uk, ying.huang@intel.com, hughd@google.com,
joey.gouly@arm.com, corbet@lwn.net, wangkefeng.wang@huawei.com,
Liam.Howlett@oracle.com, lstoakes@gmail.com,
mawupeng1@huawei.com, linmiaohe@huawei.com, namit@vmware.com,
peterx@redhat.com, peterz@infradead.org, ryan.roberts@arm.com,
shr@devkernel.io, vbabka@suse.cz, xiujianfeng@huawei.com,
yu.ma@intel.com, zhangpeng362@huawei.com, dave.hansen@intel.com,
luto@kernel.org, linux-hardening@vger.kernel.org
Subject: Re: [RFC PATCH v1 0/8] Introduce mseal() syscall
Date: Mon, 23 Oct 2023 10:44:16 -0700 [thread overview]
Message-ID: <CABi2SkVqyBgh2JpvFj3yhu8UB-p7R9euvkJAjysmn1sR_NMwsA@mail.gmail.com> (raw)
In-Reply-To: <CAHk-=wgDv5vPx2xoxNQh+kbvLsskWubGGGK69cqF_i4FkM-GCw@mail.gmail.com>
On Thu, Oct 19, 2023 at 4:06 PM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> On Thu, 19 Oct 2023 at 15:47, Pedro Falcato <pedro.falcato@gmail.com> wrote:
> > >
> > > For mprotect()/mmap(), is Linux implementation limited by POSIX ?
> >
> > No. POSIX works merely as a baseline that UNIX systems aim towards.
> > You can (and very frequently do) extend POSIX interfaces (in fact,
> > it's how most of POSIX was written, through sheer
> > "design-by-committee" on a bunch of UNIX systems' extensions).
>
> We can in extreme circumstances actually go further than that, and not
> only extend on POSIX requirements, but actively even violate them.
>
> It does need a very good reason, though, but it has happened when
> POSIX requirements were simply actively wrong.
>
> For example, at one point POSIX required
>
> int accept(int s, struct sockaddr *addr, size_t *addrlen);
>
> which was simply completely wrong. It's utter shite, and didn't
> actually match any reality.
>
> The 'addrlen' parameter is 'int *', and POSIX suddenly trying to make
> it "size_t" was completely unacceptable.
>
> So we ignored it, told POSIX people that they were full of sh*t, and
> they eventually fixed it in the next version (by introducing a
> "socklen_t" that had better be the same as "int").
>
> So POSIX can simply be wrong.
>
> Also, if it turns out that we had some ABI that wasn't
> POSIX-compatible, the whole "don't break user space" will take
> precedence over any POSIX concerns, and we will not "fix" our system
> call if people already use our old semantics.
>
> So in that case, we generally end up with a new system call (or new
> flags) instead.
>
> Or sometimes it just is such a small detail that nobody cares - POSIX
> also has a notion of documenting areas of non-conformance, and people
> who really care end up having notions like "conformance vs _strict_
> conformance".
>
> Linus
>
Thanks Linus for clarifying the guidelines on POSIX in Linux.
-Jeff
next prev parent reply other threads:[~2023-10-23 17:44 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-16 14:38 [RFC PATCH v1 0/8] Introduce mseal() syscall jeffxu
2023-10-16 14:38 ` [RFC PATCH v1 1/8] Add mseal syscall jeffxu
2023-10-16 15:05 ` Greg KH
2023-10-17 6:50 ` Jeff Xu
2023-10-16 14:38 ` [RFC PATCH v1 2/8] Wire up " jeffxu
2023-10-16 14:38 ` [RFC PATCH v1 3/8] mseal: add can_modify_mm and can_modify_vma jeffxu
2023-10-16 14:38 ` [RFC PATCH v1 4/8] mseal: seal mprotect jeffxu
2023-10-16 14:38 ` [RFC PATCH v1 5/8] mseal munmap jeffxu
2023-10-16 14:38 ` [RFC PATCH v1 6/8] mseal mremap jeffxu
2023-10-16 14:38 ` [RFC PATCH v1 7/8] mseal mmap jeffxu
2023-10-16 14:38 ` [RFC PATCH v1 8/8] selftest mm/mseal mprotect/munmap/mremap/mmap jeffxu
2023-10-16 15:18 ` [RFC PATCH v1 0/8] Introduce mseal() syscall Matthew Wilcox
2023-10-17 8:34 ` Jeff Xu
2023-10-17 12:56 ` Matthew Wilcox
2023-10-17 15:29 ` Pedro Falcato
2023-10-17 21:33 ` Jeff Xu
2023-10-17 22:35 ` Pedro Falcato
2023-10-18 18:20 ` Jeff Xu
2023-10-19 17:30 ` Jeff Xu
2023-10-19 22:47 ` Pedro Falcato
2023-10-19 23:06 ` Linus Torvalds
2023-10-23 17:44 ` Jeff Xu [this message]
2023-10-23 17:42 ` Jeff Xu
2023-10-16 17:23 ` Linus Torvalds
2023-10-17 9:07 ` Jeff Xu
2023-10-17 17:22 ` Linus Torvalds
2023-10-17 18:20 ` Theo de Raadt
2023-10-17 18:38 ` Linus Torvalds
2023-10-17 18:55 ` Theo de Raadt
2023-10-19 8:00 ` Stephen Röttger
2023-10-20 16:27 ` Theo de Raadt
2023-10-24 10:42 ` Stephen Röttger
2023-10-17 23:01 ` Jeff Xu
2023-10-17 23:56 ` Theo de Raadt
2023-10-18 3:18 ` Jeff Xu
2023-10-18 3:37 ` Theo de Raadt
2023-10-18 15:17 ` Matthew Wilcox
2023-10-18 18:54 ` Jeff Xu
2023-10-18 20:36 ` Theo de Raadt
2023-10-19 8:28 ` Stephen Röttger
2023-10-20 15:55 ` Theo de Raadt
2023-10-16 17:34 ` Jann Horn
2023-10-17 8:42 ` Jeff Xu
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