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Date: Fri, 22 Feb 2013 22:58:18 -0500
From: KOSAKI Motohiro <kosaki.motohiro@...il.com>
To: Rich Felker <dalias@...ifal.cx>
Cc: libc-alpha <libc-alpha@...rceware.org>, musl@...ts.openwall.com
Subject: Re: O_EXEC and O_SEARCH
On Fri, Feb 22, 2013 at 10:17 PM, Rich Felker <dalias@...ifal.cx> wrote:
> On Fri, Feb 22, 2013 at 10:05:03PM -0500, KOSAKI Motohiro wrote:
>> > I'd like to have a conversation with the glibc team about O_EXEC and
>> > O_SEARCH in the interest of hopefully developing a unified plan for
>> > supporting them on Linux. Presumably the reason glibc still does not
>> > have them is that Linux O_PATH does not exactly match their semantics
>> > in some cases, and O_PATH is sufficiently broken on many kernel
>> > versions to make offering it problematic. In particular, current
>> > coreutils break badly on most kernel versions around 2.6.39-3.6 or so
>> > if O_SEARCH and O_EXEC are defined as O_PATH.
>>
>> I'm curious why don't you implement them in kernel directly?
>
> See this thread for Linus's opinion on why O_SEARCH was not added:
>
> http://comments.gmane.org/gmane.linux.file-systems/33611
>
> O_NODE seems to have been renamed to O_PATH, or perhaps O_PATH was a
> later independent implementation of the same idea; it's not clear to
> me which happened. But the idea is that the kernel folks did not want
> to do O_SEARCH and O_EXEC properly in kernelspace but instead wanted
> to provide a more general flag that could be used to implement both
> O_SEARCH and O_EXEC.
Do you mean following response?
>I suspect that what we _could_ possibly do is to have something like
>O_NODE, and after that - if the semantics (for directories) match what
>O_SEARCH/O_EXEC wants, we could just do
>
>#define O_SEARCH O_NODE
>
>but my point is that we should _not_ start from O_SEARCH and make that the
>"core" part, since its semantics are badly defined (undefined) to begin
>with.
I so, I don't think "start" mean refusing at all. However, I agree
kernel folks dislike
to hear "because it's posix". As far as no concrete good use case, any proposal
may be going to be get negative response.
However, if O_SEARCH is really useful, I think in kernel
implementation is better
because all other flags are implemented in kernel and it may prevent to create
ugly corner case.
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