arm_fadvise() man page

arm_fadvise() man page

[Michael Kerrisk]

[Was: man pages for undocumented system calls]

Stephan,

The situation here is similar to sync_file_range, but specific to ARM.
The documentation would better be in the posix_fadvise() page, should
explicitly note that this system call is for ARM only, and should note
why the system call exists. For man-pages-3.29, I applied the patch
below.

Thanks,

Michael

--- a/man2/posix_fadvise.2
+++ b/man2/posix_fadvise.2
@@ -148,6 +149,30 @@ call
 or
 .BR fdatasync (2)
 first.
+.SS arm_fadvise()
+The ARM architecture
+needs 64-bit arguments to be aligned in a suitable pair of registers.
+On this architecture, the call signature of
+.BR posix_fadvise ()
+is flawed, since it forces a register to be wasted as padding between the
+.I fd
+and
+.I len
+arguments.
+Therefore, since Linux 2.6.14, ARM defines a different
+system call that orders the arguments suitably:
+.PP
+.in +4n
+.nf
+.BI "long arm_fadvise64_64(int " fd ", int " advice ,
+.BI "                     loff_t " offset ", loff_t " len );
+.fi
+.in
+.PP
+The behavior of this system call is otherwise exactly the same as
+.BR posix_fadvise().
+No library support is provided for this system call in glibc.
+.\" No ARM support in glibc.
 .SH BUGS
 In kernels before 2.6.6, if
 .I len

-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Author of "The Linux Programming Interface"; http://man7.org/tlpi/
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Re: arm_fadvise() man page

[Stephan Mueller]

Am Samstag, 9. Oktober 2010, um 06:50:29 schrieb Michael Kerrisk:

Hi Michael,

> [Was: man pages for undocumented system calls]
> 
> Stephan,
> 
> The situation here is similar to sync_file_range, but specific to ARM.
> The documentation would better be in the posix_fadvise() page, should
> explicitly note that this system call is for ARM only, and should note
> why the system call exists. For man-pages-3.29, I applied the patch
> below.

Same here, I think your approach is better than a stand-alone man page.

Nevertheless, are you going to please add a symlink from posix_fadvise.2.gz to 
arm_fadvise.2.gz?

Thanks
Stephan

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Re: arm_fadvise() man page

[Michael Kerrisk]

Hi Stephan,

On Sat, Oct 9, 2010 at 2:40 PM, Stephan Mueller
<stephan.mueller-fwYZOkdEjagAvxtiuMwx3w@public.gmane.org> wrote:
> Am Samstag, 9. Oktober 2010, um 06:50:29 schrieb Michael Kerrisk:
>
> Hi Michael,
>
>> [Was: man pages for undocumented system calls]
>>
>> Stephan,
>>
>> The situation here is similar to sync_file_range, but specific to ARM.
>> The documentation would better be in the posix_fadvise() page, should
>> explicitly note that this system call is for ARM only, and should note
>> why the system call exists. For man-pages-3.29, I applied the patch
>> below.
>
> Same here, I think your approach is better than a stand-alone man page.
>
> Nevertheless, are you going to please add a symlink from posix_fadvise.2.gz to
> arm_fadvise.2.gz?

Thanks for reminding me of this, but in fact I already made such a
link. I added a link arm_fadvise64_64.2, since that is the precise
name of the system call. But, on reflection, perhaps it does not hurt
to also add a link arm_fadvise.2, so I've also added that one now.

Thanks,

Michael

-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Author of "The Linux Programming Interface"; http://man7.org/tlpi/
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