linux-kernel - Re: LDD examples

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Message-Id: <20100903110158.aadf7850.rdunlap@xenotime.net>
Date:	Fri, 3 Sep 2010 11:01:58 -0700
From:	Randy Dunlap <rdunlap@...otime.net>
To:	Someone Something <fordhaivat@...il.com>
Cc:	linux-kernel@...r.kernel.org, gregkh <greg@...ah.com>,
	corbet@....net
Subject: Re: LDD examples

On Fri, 27 Aug 2010 18:32:03 -0400 Someone Something wrote:

> I downloaded the LDD examples
> (http://examples.oreilly.com/9780596005900/), and I unzipped the file
> and just tried building it with make just to see if it built properly
> and here are the errors I get:
> setlevel.c:30: error: expected declaration specifiers or '...' before 'type'
> setlevel.c:30: error: expected declaration specifiers or '...' before 'bufp'
> setlevel.c:30: error: expected declaration specifiers or '...' before 'len'
> setlevel.c:30: warning: data definition has no type or storage class
> setlevel.c:30: warning: type defaults to 'int' in declaration of '_syscall3'
> setlevel.c: In function 'main':
> setlevel.c:41: warning: implicit declaration of function 'syslog'
> 
> have any of use experienced these errors? Is this book out of date?
> Alternatives?
> --

The examples are certainly out of date.


'man 2 _syscall' says that it is obsolete and deprecated.

Fixing the userspace programs is easy.  E.g., for setlevel.c, just
#include <unistd.h> 
and change this line:

-_syscall3(int, syslog, int, type, char *, bufp, int, len);
+#define syslog(type, bufp, len)	syscall(8, type, bufp, len)


For the kernel modules, remove
#include <linux/config.h>
from all of them and change CFLAGS to EXTRA_CFLAGS in all Makefiles.

The biggest remaining problem with the kernel modules is scheduled_work
usage and its changing API.


---
~Randy
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