linux-kernel - Re: [PATCH] lseek.2: SYNOPSIS: Use correct types

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Date:   Sat, 21 Nov 2020 18:45:50 +0100
From:   "Alejandro Colomar (man-pages)" <alx.manpages@...il.com>
To:     mtk.manpages@...il.com
Cc:     linux-man@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] lseek.2: SYNOPSIS: Use correct types

Hi Michael,

I'm a bit lost in all the *lseek* pages.
You had a good read some months ago, so you may know it better.
I don't know which of those functions come from the kernel,
and which come from glibc (if any).
In the kernel I only found the lseek, llseek, and 32_llseek
(as you can see in the patch).
So if any other prototype needs to be updated, please do so.
Especially, have a look at lseek64(3),
which I suspect needs the same changes I propose in that patch.

Thanks,

Alex

On 11/21/20 6:30 PM, Alejandro Colomar wrote:
> The Linux kernel uses 'unsigned int' instead of 'int'
> for 'fd' and 'whence'.
> As glibc provides no wrapper, use the same types the kernel uses.
> 
> src/linux$ grep -rn "SYSCALL_DEFINE.*lseek"
> fs/read_write.c:322:SYSCALL_DEFINE3(lseek, unsigned int, fd, off_t, offset, unsigned int, whence)
> fs/read_write.c:328:COMPAT_SYSCALL_DEFINE3(lseek, unsigned int, fd, compat_off_t, offset, unsigned int, whence)
> fs/read_write.c:336:SYSCALL_DEFINE5(llseek, unsigned int, fd, unsigned long, offset_high,
> arch/mips/kernel/linux32.c:65:SYSCALL_DEFINE5(32_llseek, unsigned int, fd, unsigned int, offset_high,
> 
> src/linux$ sed -n 322,325p fs/read_write.c
> SYSCALL_DEFINE3(lseek, unsigned int, fd, off_t, offset, unsigned int, whence)
> {
> 	return ksys_lseek(fd, offset, whence);
> }
> 
> Signed-off-by: Alejandro Colomar <alx.manpages@...il.com>
> ---
>  man2/lseek.2 | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/man2/lseek.2 b/man2/lseek.2
> index e35e410a6..2ff878ffa 100644
> --- a/man2/lseek.2
> +++ b/man2/lseek.2
> @@ -51,7 +51,7 @@ lseek \- reposition read/write file offset
>  .br
>  .B #include <unistd.h>
>  .PP
> -.BI "off_t lseek(int " fd ", off_t " offset ", int " whence );
> +.BI "off_t lseek(unsigned int " fd ", off_t " offset ", unsigned int " whence );
>  .SH DESCRIPTION
>  .BR lseek ()
>  repositions the file offset of the open file description
>