From: "Arnd Bergmann" <arnd@arndb.de>
To: "Zhangjin Wu" <falcon@tinylab.org>, "Willy Tarreau" <w@1wt.eu>
Cc: linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org,
linux-riscv@lists.infradead.org,
"Thomas Weißschuh" <thomas@t-8ch.de>
Subject: Re: [PATCH v2 07/13] tools/nolibc: sys_lseek: add pure 64bit lseek
Date: Tue, 30 May 2023 10:10:16 +0200 [thread overview]
Message-ID: <5e7d2adf-e96f-41ca-a4c6-5c87a25d4c9c@app.fastmail.com> (raw)
In-Reply-To: <2f5c3338898da65210ad3f62d7b7773a96f6d251.1685387484.git.falcon@tinylab.org>
On Mon, May 29, 2023, at 21:54, Zhangjin Wu wrote:
> use sys_llseek instead of sys_lseek to add 64bit seek even in 32bit
> platforms.
>
> This code is based on sysdeps/unix/sysv/linux/lseek.c of glibc and
> src/unistd/lseek.c of musl.
>
> Signed-off-by: Zhangjin Wu <falcon@tinylab.org>
> Signed-off-by: Willy Tarreau <w@1wt.eu>
> ---
> tools/include/nolibc/sys.h | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/tools/include/nolibc/sys.h b/tools/include/nolibc/sys.h
> index 98cfa2f6d021..d0720af84b6d 100644
> --- a/tools/include/nolibc/sys.h
> +++ b/tools/include/nolibc/sys.h
> @@ -672,7 +672,17 @@ int link(const char *old, const char *new)
> static __attribute__((unused))
> off_t sys_lseek(int fd, off_t offset, int whence)
> {
> +#if defined(__NR_llseek) || defined(__NR__llseek)
> +#ifndef __NR__llseek
> +#define __NR__llseek __NR_llseek
> +#endif
> + off_t result;
> + return my_syscall5(__NR__llseek, fd, offset >> 32, offset, &result,
> whence) ?: result;
> +#elif defined(__NR_lseek)
> return my_syscall3(__NR_lseek, fd, offset, whence);
> +#else
> +#error None of __NR_lseek, __NR_llseek nor __NR__llseek defined,
> cannot implement sys_lseek()
> +#endif
> }
This is not technically wrong, but I think a different approach
would be clearer: Instead of having a sys_lseek() that works
differently depending on the macros, why not define the low-level
helpers to match the kernel arguments like
static inline __attribute__((unused))
__kernel_loff_t sys_lseek(int fd, __kernel_loff_t offset, int whence)
{
#ifdef __NR__llseek
__kernel_loff_t result;
return my_syscall5(__NR__llseek, fd, offset >> 32, offset, &result, whence) ?: result;
#else
#endif
}
static inline __attribute__((unused))
__kernel_off_t sys_lseek(int fd, __kernel_off_t offset, int whence)
{
#ifdef __NR_lseek
return my_syscall3(__NR_lseek, fd, offset, whence);
#else
return -ENOSYS;
#endif
}
And then do the selection inside of the actual lseek,
something like
static __attribute__((unused))
off_t lseek(int fd, off_t offset, int whence)
{
off_t ret = -ENOSYS;
if (BITS_PER_LONG == 32)
ret = sys_llseek(fd, offset, whence);
if (ret == -ENOSYS)
ret = sys_lseek(fd, offset, whence);
if (ret < 0) {
SET_ERRNO(-ret);
ret = -1;
}
return ret;
}
For the loff_t selection, there is no real need to handle the
fallback, so this could just be an if()/else to select 32-bit
or 64-bit, but for the time_t ones the fallback is required
for pre-5.6 kernels.
Arnd
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next prev parent reply other threads:[~2023-05-30 8:10 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-29 19:45 [PATCH v2 00/13] nolibc: add part2 of support for rv32 Zhangjin Wu
2023-05-29 19:46 ` [PATCH v2 01/13] selftests/nolibc: remove gettimeofday_bad1/2 completely Zhangjin Wu
2023-05-29 19:47 ` [PATCH v2 02/13] selftests/nolibc: support two errnos with EXPECT_SYSER2() Zhangjin Wu
2023-05-29 19:49 ` [PATCH v2 03/13] selftests/nolibc: waitpid_min: add waitid syscall support Zhangjin Wu
2023-05-29 19:50 ` [PATCH v2 04/13] tools/nolibc: add missing nanoseconds support for __NR_statx Zhangjin Wu
2023-05-29 21:39 ` Thomas Weißschuh
2023-05-30 5:21 ` Zhangjin Wu
2023-05-29 19:51 ` [PATCH v2 05/13] tools/nolibc: add more wait status related types Zhangjin Wu
2023-05-29 19:53 ` [PATCH v2 06/13] tools/nolibc: add pure 64bit off_t, time_t and blkcnt_t Zhangjin Wu
2023-05-29 19:54 ` [PATCH v2 07/13] tools/nolibc: sys_lseek: add pure 64bit lseek Zhangjin Wu
2023-05-30 8:10 ` Arnd Bergmann [this message]
2023-05-30 13:54 ` Zhangjin Wu
2023-07-02 16:28 ` Willy Tarreau
2023-05-29 19:56 ` [PATCH v2 08/13] tools/nolibc: add pure 64bit time structs Zhangjin Wu
2023-05-29 19:57 ` [PATCH v2 09/13] tools/nolibc: sys_select: add pure 64bit select Zhangjin Wu
2023-05-29 19:58 ` [PATCH v2 10/13] tools/nolibc: sys_poll: add pure 64bit poll Zhangjin Wu
2023-05-29 19:59 ` [PATCH v2 11/13] tools/nolibc: sys_gettimeofday: add pure 64bit gettimeofday Zhangjin Wu
2023-05-29 20:01 ` [PATCH v2 12/13] tools/nolibc: sys_wait4: add waitid syscall support Zhangjin Wu
2023-05-29 20:03 ` [PATCH v2 13/13] selftests/nolibc: riscv: customize makefile for rv32 Zhangjin Wu
2023-06-02 4:06 ` Zhangjin Wu
2023-06-02 10:33 ` Thomas Weißschuh
2023-06-02 11:56 ` Zhangjin Wu
2023-05-30 6:33 ` [PATCH v2 0/2] nolibc: add part3 of support " Zhangjin Wu
2023-05-30 6:37 ` [PATCH 1/2] selftests/nolibc: add new gettimeofday test cases Zhangjin Wu
2023-05-30 10:59 ` Thomas Weißschuh
2023-05-30 11:28 ` Zhangjin Wu
2023-05-30 11:54 ` Thomas Weißschuh
2023-05-30 12:05 ` Willy Tarreau
2023-05-30 12:31 ` Andreas Schwab
2023-05-30 12:35 ` Thomas Weißschuh
2023-05-30 6:42 ` [PATCH 2/2] selftests/nolibc: add sizeof test for the new 64bit data types Zhangjin Wu
2023-05-30 9:18 ` Thomas Weißschuh
2023-05-30 11:17 ` Zhangjin Wu
2023-06-02 19:44 ` [PATCH v2 00/13] nolibc: add part2 of support for rv32 Willy Tarreau
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