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Date: Mon, 2 Mar 2026 23:30:57 +0100
From: Thomas =?utf-8?Q?Wei=C3=9Fschuh?= <linux@weissschuh.net>
To: Jordan Richards <jordanrichards@google.com>
Cc: dmatlack@google.com, jasonmiu@google.com, linux-kernel@vger.kernel.org, 
	linux-kselftest@vger.kernel.org, linux-mm@kvack.org, pasha.tatashin@soleen.com, 
	pratyush@kernel.org, rppt@kernel.org, shuah@kernel.org, w@1wt.eu
Subject: Re: [PATCH v2 1/2] tools/nolibc: add ftruncate()
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References: <ebf0c9fd-9c45-4aa2-8cd7-fe8d5956ce52@t-8ch.de>
 <20260302222043.2432413-1-jordanrichards@google.com>
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In-Reply-To: <20260302222043.2432413-1-jordanrichards@google.com>

On 2026-03-02 22:20:43+0000, Jordan Richards wrote:

(...)

> > off_t is now always 64bit on nolibc. On 32-bit architectures however
> > __NR_ftruncate only takes a 32bit value, leading to the wrong kind of
> > truncation. Use __NR_ftruncate64 instead where available.
> 
> Good call. On some archs (arm, mips, ppc) register pairs need to start
> in an even register. I assume adding a flag like:
> 
>   #define ARCH_ALIGN_REGISTER_PAIR 1
> 
> in "nolibc/arch-xxx.h" is appropriate?

I would use a custom sys_ftruncate64() wrapper function for those.
Similar to sys_mmap() on some architectures or sys_fork() on s390.

(...)

Thomas