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From: "fweimer at redhat dot com" <sourceware-bugzilla@sourceware.org>
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Subject: [Bug libc/23960] [2.28 Regression]: New getdents{64} implementation
 breaks qemu-user
Date: Fri, 02 Oct 2020 09:46:51 +0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D23960

--- Comment #60 from Florian Weimer <fweimer at redhat dot com> ---
(In reply to Danny Milosavljevic from comment #59)
> It's impossible to store a 64 bit result into a 32 bit slot.

You can do something like that if you can maintain a translation table. The
kernel cannot do it due to the way the getdents64 system call works. glibc =
can
do it for telldir/seekdir (allocating table slots on demand), which are the
interfaces that are actually problematic.

> Please don't use SYS_getdents.  Just please mandate LFS instead.  This sh=
ould have been done long (decades) ago.

LFS does not change the return type of telldir. So it does not fix the issu=
e.
We need to maintain a translation table for telldir and seekdir in DIR. It =
can
be filled on demand, so that applications that do not call telldir are pret=
ty
much unaffected. The only thing that is a bit tricky is that we have to
pre-allocate the slot during readdir because telldir must not fail.

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