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Re: d_off field in struct dirent and 32-on-64 emulation
- From: Joseph Myers <joseph at codesourcery dot com>
- To: Adhemerval Zanella <adhemerval dot zanella at linaro dot org>
- Cc: Florian Weimer <fw at deneb dot enyo dot de>, <linux-fsdevel at vger dot kernel dot org>, <linux-api at vger dot kernel dot org>, <linux-ext4 at vger dot kernel dot org>, <linux-kernel at vger dot kernel dot org>, <v9fs-developer at lists dot sourceforge dot net>, <libc-alpha at sourceware dot org>, <qemu-devel at nongnu dot org>, <ericvh at gmail dot com>, <rminnich at sandia dot gov>, <lucho at ionkov dot net>, <hpa at zytor dot com>, <arnd at arndb dot de>
- Date: Mon, 31 Dec 2018 17:03:40 +0000
- Subject: Re: d_off field in struct dirent and 32-on-64 emulation
- References: <87bm56vqg4.fsf@mid.deneb.enyo.de> <957967d7-5717-8ada-fb30-dfdf19898b6b@linaro.org> <87pntmu9iw.fsf@mid.deneb.enyo.de> <ae0530c9-5c46-5560-9734-1eacaf173b8d@linaro.org>
On Fri, 28 Dec 2018, Adhemerval Zanella wrote:
> >> Currently we only have nios2 and csky (unfortunately). But since generic
> >> definition for off_t and off64_t still assumes non-LFS support, all new
> >> 32-bits ports potentially might carry the issue.
> >
> > For csky, we could still change the type of the non-standard d_off
> > field to long long int. This way, only telldir would have to fail
> > when truncation is necessary, as mentioned below:
>
> I think it makes no sense to continue making non-LFS as default for
> newer 32 bits ports, the support will be emulated with LFS syscalls.
Any new 32-bit port that uses 64-bit time_t will also use 64-bit offsets
(because we don't have any glibc configurations that support the
combination of 64-bit time with 32-bit offsets, and don't want to add
them). That should apply for RISC-V 32-bit at least.
I've filed <https://sourceware.org/bugzilla/show_bug.cgi?id=24050> for
missing overflow checks in telldir when the default off_t is wider than
long int (currently just applies to x32; not sure why we don't see glibc
test failures on x32 resulting from the quiet truncation, as the issue is
certainly there in the source code).
--
Joseph S. Myers
joseph@codesourcery.com