linux-kernel - Re: d_off field in struct dirent and 32-on-64 emulation

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Date:   Wed, 2 Jan 2019 11:16:37 -0200
From:   Adhemerval Zanella <adhemerval.zanella@...aro.org>
To:     Joseph Myers <joseph@...esourcery.com>
Cc:     Florian Weimer <fw@...eb.enyo.de>, linux-fsdevel@...r.kernel.org,
        linux-api@...r.kernel.org, linux-ext4@...r.kernel.org,
        linux-kernel@...r.kernel.org, v9fs-developer@...ts.sourceforge.net,
        libc-alpha@...rceware.org, qemu-devel@...gnu.org, ericvh@...il.com,
        rminnich@...dia.gov, lucho@...kov.net, hpa@...or.com, arnd@...db.de
Subject: Re: d_off field in struct dirent and 32-on-64 emulation



On 31/12/2018 15:03, Joseph Myers wrote:
> 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).
> 

What about csky? Should we still make it use 32-bit offsets as default
configuration even when kernel does not support it natively?