_syscall2 vs MAX_ERRNO

_syscall2 vs MAX_ERRNO

[Mark Wielaard]

[-- Attachment #1: Type: text/plain, Size: 521 bytes --]

Hi,

On new (FC6) x86_64 (2.6.19 kernel) systems when you try to import
linux/unistd.h to get a definition of _syscall2 it is defined in terms
that use MAX_ERRNO. Unfortunately this constant isn't anywhere defined
in a user visible header as far as I can tell. So for now I have
installed the following patch to get things compiling again.

2007-01-23  Mark Wielaard  <mark@klomp.org>

       * include/linux.syscall.h: Define MAX_ERRNO if not yet defined.

Hints and tips for a real solution appreciated.

Cheers,

Mark

[-- Attachment #2: Type: text/x-patch, Size: 666 bytes --]

? max_errno.patch
Index: include/linux.syscall.h
===================================================================
RCS file: /cvs/frysk/frysk-imports/include/linux.syscall.h,v
retrieving revision 1.4
diff -u -r1.4 linux.syscall.h
--- include/linux.syscall.h	4 Sep 2006 13:06:57 -0000	1.4
+++ include/linux.syscall.h	23 Jan 2007 11:42:30 -0000
@@ -43,6 +43,13 @@
 #include <errno.h>
 #include <linux/unistd.h>
 
+/* If linux/unistd.h defines _syscall2 then it might refer to MAX_ERRNO
+ * which might not be defined anywhere (at least it does so on x86_64).
+ */
+#ifndef MAX_ERRNO
+#define MAX_ERRNO 4095
+#endif
+
 /* Declares syscall() */
 #include <unistd.h>
 

Re: _syscall2 vs MAX_ERRNO

[Andrew Cagney]

Mark,

This gets weird.  The syscall macros were removed which is why 
include/linux.syscall.h contains simple versions.  Sounds like they are 
back!?! The tkill man page, on fc6, notes:

       _syscall2(int, tkill, int, tid, int, sig)
                 /* Using syscall(2) may be preferable; see intro(2) */

from you're notes, this doesn't work.  I'd file a bug both with frysk 
and with the relevant distro.  Otherwize, yea, that file is a kludge anyway.

Andrew

Mark Wielaard wrote:
> Hi,
>
> On new (FC6) x86_64 (2.6.19 kernel) systems when you try to import
> linux/unistd.h to get a definition of _syscall2 it is defined in terms
> that use MAX_ERRNO. Unfortunately this constant isn't anywhere defined
> in a user visible header as far as I can tell. So for now I have
> installed the following patch to get things compiling again.
>
> 2007-01-23  Mark Wielaard  <mark@klomp.org>
>
>        * include/linux.syscall.h: Define MAX_ERRNO if not yet defined.
>
> Hints and tips for a real solution appreciated.
>
> Cheers,
>
> Mark
>   
> ------------------------------------------------------------------------
>
> ? max_errno.patch
> Index: include/linux.syscall.h
> ===================================================================
> RCS file: /cvs/frysk/frysk-imports/include/linux.syscall.h,v
> retrieving revision 1.4
> diff -u -r1.4 linux.syscall.h
> --- include/linux.syscall.h	4 Sep 2006 13:06:57 -0000	1.4
> +++ include/linux.syscall.h	23 Jan 2007 11:42:30 -0000
> @@ -43,6 +43,13 @@
>  #include <errno.h>
>  #include <linux/unistd.h>
>  
> +/* If linux/unistd.h defines _syscall2 then it might refer to MAX_ERRNO
> + * which might not be defined anywhere (at least it does so on x86_64).
> + */
> +#ifndef MAX_ERRNO
> +#define MAX_ERRNO 4095
> +#endif
> +
>  /* Declares syscall() */
>  #include <unistd.h>
>  
>   

Re: _syscall2 vs MAX_ERRNO

[Roland McGrath]

Don't use those macros.  Use the syscall function.

Re: _syscall2 vs MAX_ERRNO

[Mark Wielaard]

On Tue, 2007-01-23 at 09:38 -0500, Andrew Cagney wrote:
> Mark,
> 
> This gets weird.  The syscall macros were removed which is why 
> include/linux.syscall.h contains simple versions.  Sounds like they are 
> back!?! The tkill man page, on fc6, notes:
> 
>        _syscall2(int, tkill, int, tid, int, sig)
>                  /* Using syscall(2) may be preferable; see intro(2) */
> 
> from you're notes, this doesn't work.  I'd file a bug both with frysk 
> and with the relevant distro.  Otherwize, yea, that file is a kludge anyway.

This is now frysk bug #3912. And upstream
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=224130

Cheers,

Mark