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From: Julian Elischer <julian@FreeBSD.org>
Date: Fri, 18 Mar 2016 07:59:39 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
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Subject: svn commit: r297012 - head/share/man/man9
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Author: julian
Date: Fri Mar 18 07:59:38 2016
New Revision: 297012
URL: https://svnweb.freebsd.org/changeset/base/297012

Log:
  Add a few details that make it easier to use this macro.
  
  MFC after:	1 week
  Sponsored by:	Panzura inc

Modified:
  head/share/man/man9/SYSCALL_MODULE.9

Modified: head/share/man/man9/SYSCALL_MODULE.9
==============================================================================
--- head/share/man/man9/SYSCALL_MODULE.9	Fri Mar 18 07:13:09 2016	(r297011)
+++ head/share/man/man9/SYSCALL_MODULE.9	Fri Mar 18 07:59:38 2016	(r297012)
@@ -57,6 +57,8 @@ A pointer to an
 which saves the offset in
 .Vt "struct sysent"
 where the syscall is allocated.
+If the location pointed to by offset holds a non 0 number it will be used if possible.
+If it holds 0 then one will be assigned.
 .It Fa new_sysent
 is a pointer to a structure that specifies the function implementing
 the syscall and the number of arguments this function needs (see
@@ -72,6 +74,17 @@ The argument passed to the callback func
 .Fa evh
 event handler when it is called.
 .El
+.Pp
+The syscall number assigned to the module can be retrieved using the
+.Xr modstat 3
+and
+.Xr modfind 3
+library functions in libc.
+The MACRO
+.Fn SYSCALL_MODULE_HELPER
+includes 
+.Fn SYSCALL_MODULE
+and much of its boilerplate code.
 .Sh EXAMPLES
 A minimal example for a syscall module can be found in
 .Pa /usr/share/examples/kld/syscall/module/syscall.c .