linux-kernel - Re: [PATCH 07/17] riscv: vdso: Switch to generic storage implementation

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Message-Id: <0bdeda72-73e6-4749-8d54-66c7614a6f83@app.fastmail.com>
Date: Thu, 19 Dec 2024 08:03:24 +0100
From: "Arnd Bergmann" <arnd@...db.de>
To: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
Cc: "Conor Dooley" <conor@...nel.org>,
 "James E . J . Bottomley" <James.Bottomley@...senpartnership.com>,
 "Helge Deller" <deller@....de>, "Andy Lutomirski" <luto@...nel.org>,
 "Thomas Gleixner" <tglx@...utronix.de>,
 "Vincenzo Frascino" <vincenzo.frascino@....com>,
 "Anna-Maria Gleixner" <anna-maria@...utronix.de>,
 "Frederic Weisbecker" <frederic@...nel.org>,
 "Andrew Morton" <akpm@...ux-foundation.org>,
 "Catalin Marinas" <catalin.marinas@....com>,
 "Will Deacon" <will@...nel.org>, "Theodore Ts'o" <tytso@....edu>,
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 "H. Peter Anvin" <hpa@...or.com>, linux-parisc@...r.kernel.org,
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 "Nam Cao" <namcao@...utronix.de>
Subject: Re: [PATCH 07/17] riscv: vdso: Switch to generic storage implementation

On Thu, Dec 19, 2024, at 07:30, Thomas Weißschuh wrote:
> On Wed, Dec 18, 2024 at 05:35:31PM +0100, Arnd Bergmann wrote:
>>
>> > There is precedence in providing 64bit only vDSO functions, for example
>> > __vdso_clock_gettime64() in arm.
>> > I do have a small, so far untested, proof-of-concept patch for it.
>> > This would even be less code than the ifdefs.
>> >
>> > What do you think about it?
>> 
>> Yes, simply exposing the normal time64 syscalls through vdso
>> should be fine. I think this currently works on everything except
>> rv32 and sparc32, probably because neither of them have actual
>> users that are able to test.
>
> Should it use the specific _vdso_clock_gettime64() naming or leave out
> the 64 suffix?

The VDSO function name should match the syscall name, with the '64'
suffix. Any syscall ending in _time64 uses the __kernel_time64_t
derived types, while the corresponding syscall names that don't end
in _time64 take a __kernel_old_time_t, which is defined as
__kernel_long_t and only 32 bits wide.

      Arnd