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Date:   Fri, 26 May 2023 11:34:46 +0200
From:   "Arnd Bergmann" <arnd@arndb.de>
To:     =?UTF-8?Q?Thomas_Wei=C3=9Fschuh?= <thomas@t-8ch.de>,
        "Zhangjin Wu" <falcon@tinylab.org>
Cc:     "Willy Tarreau" <w@1wt.eu>, linux-kernel@vger.kernel.org,
        linux-kselftest@vger.kernel.org, linux-riscv@lists.infradead.org,
        "Palmer Dabbelt" <palmer@dabbelt.com>,
        "Paul Walmsley" <paul.walmsley@sifive.com>
Subject: Re: [PATCH 09/13] tools/nolibc: sys_poll: riscv: use __NR_ppoll_time64 for
 rv32
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On Fri, May 26, 2023, at 09:15, Thomas Wei=C3=9Fschuh wrote:
> On 2023-05-25 01:57:24+0800, Zhangjin Wu wrote:
>> rv32 uses the generic include/uapi/asm-generic/unistd.h and it has no

>> =20
>> +/* needed by time64 syscalls */
>> +struct timespec64 {
>> +	time64_t	tv_sec;		/* seconds */
>> +	long		tv_nsec;	/* nanoseconds */
>> +};
>
> A question to you and Willy, as it's also done the same for other type=
s:
>
> What is the advantage of custom definitions over using the one from the
> kernel (maybe via a typedef).
>
> From linux/time_types.h:
>
> struct __kernel_timespec {
> 	__kernel_time64_t tv_set;
> 	long long tv_nsec;
> };

I agree the __kernel_* types are what we should be using when
interacting with system calls directly, that is definitely what
they are intended for.

I would go further here and completely drop support for 32-bit
time_t/off_t and derived types in nolibc. Unfortunately, the
kernel's include/uapi/linux/time.h header still defines the
old types, this is one of the last remnants the time32 syscalls
definitions in the kernel headers, and this already conflicts
with the glibc and musl definitions, so anything that includes
this header is broken on real systems. I think it makes most
sense for nolibc to just use the linux/time_types.h header
instead and use something like

#define timespec   __kernel_timespec
#define itimerspec __kernel_itimerspec
typedef __kernel_time64_t time_t;
/* timeval is only provided for users, not compatible with syscalls */
struct timeval { __kernel_time64_t tv_sec; __s64 tv_nsec; };

so we can drop all the fallbacks for old 32-bit targets. This
also allows running with CONFIG_COMPAT_32BIT_TIME disabled.

     Arnd