RE: Simple LKM & copy_from_user question (followup)

RE: Simple LKM & copy_from_user question (followup)

[David CM Weber]

[-- Attachment #1: Type: text/plain, Size: 1685 bytes --]

Attached is the file I"m having problems with.  I'm compiling it w/ 

gcc -O3 -c main.c

Thanks in advance,


Dave Weber
Backbone Security, Inc.
570-422-7900





> -----Original Message-----
> From: David CM Weber 
> Sent: Friday, July 20, 2001 12:45 PM
> To: linux-kernel@vger.kernel.org
> Subject: Simple LKM & copy_from_user question
> 
> 
> Hello all.  I've been lurking for a while, and I have a quick 
> question.
> I'm in the process of writing my first LKM to mess with the
> sys_socketcall function.  I'm looking at the original one for 
> guidance,
> and it makes a call to copy_from_user() to get some 
> socket-related data.
> 
> So, to use copy_from_user(), I've gathered that I need to #include
> <asm/uaccess.h>, so I do so.  
> 
> After including this file, I'm getting the following errors:
> 
> 
> .../linux/timer.h:21: field 'vec' has incomplete type
> 
> .../asm/uaccess.h::63: dereferencing pointer to incomplete type
> 
> 
> (This is not a full list of the error message that it's reporting)
> 
> Am I not setting a define correctly? 
> 
> I'm using Redhat 7.1, on an Intel P3 system.  It's the latest stable
> release (2.4.x ??) of the kernel.
> 
> 
> 
> If you need more information, please let me know.  This has been
> troubling me for several days now..
> 
> 
> Thanks,
> 
> 
> Dave Weber
> Backbone Security, Inc.
> 570-422-7900
> -
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> 

[-- Attachment #2: main.c --]
[-- Type: application/octet-stream, Size: 1904 bytes --]

#define MODULE // this is a LKM
#include <linux/module.h> // for Module access
//#include <linux/kernel.h> // For kernel access
#include <sys/syscall.h> // for the SYS_socketcall value

#include <linux/net.h> // For the various sys_socketcall parameters
//#include <asm/unistd.h>
#include <asm/errno.h> // For the error return values
#include <asm/uaccess.h> // for copy_from_user



// Define a debug print statement
#define BBPRINT(a) printk("%s(%i): %s\n", __FILE__, __LINE__, a)
 
// Type define a byte -> unsigned char
typedef unsigned char byte;

// Our friendly neighborhood system call table
extern void* sys_call_table[];

// Taken from socket.c
// Argument list sizes for sys_socketcall
#define AL(x) ((x) * sizeof(unsigned long))
static unsigned char nargs[18]={AL(0),AL(3),AL(3),AL(3),AL(2),AL(3),
				AL(3),AL(3),AL(4),AL(4),AL(4),AL(6),
				AL(6),AL(2),AL(5),AL(5),AL(3),AL(3)};


// Create our orginal function pointer
int (*original_socketcall)(int call, unsigned long *args);

// Our function's advance declaration
int my_socketcall(int call, unsigned long *args);

int init_module(void)
{
	BBPRINT("Loading Socket LKM");

	// Save the original location	
	original_socketcall = sys_call_table[SYS_socketcall];

	// Replace the table entry with our socketcall
	sys_call_table[SYS_socketcall] = my_socketcall; 

	return 0;
}

// This is run when the module is unloaded
void cleanup_module(void)
{
	//Go back to the orignal socketcall
	sys_call_table[SYS_socketcall] = original_socketcall;

	BBPRINT("Unloading Socket LKM");
}


int my_socketcall(int call, unsigned long *args)
{
	unsigned long a[6];
	unsigned long a0,a1;

	int err;

	if(call < 1 || call > SYS_RECVMSG)
		return -EINVAL;

	// copy_from_user should be SMP safe.
	if (copy_from_user(a, args, nargs[call]))
		return -EFAULT;
		
	a0=a[0];
	a1=a[1];


	// Call the original function
	return(original_socketcall(call, args));
}

RE: Simple LKM & copy_from_user question (followup)

[Richard B. Johnson]

On Fri, 20 Jul 2001, David CM Weber wrote:

> Attached is the file I"m having problems with.  I'm compiling it w/ 
> 
> gcc -O3 -c main.c
> 
> Thanks in advance,
> 
> 
> Dave Weber
> Backbone Security, Inc.
> 570-422-7900
> 

Top line:

#define __KERNEL__

... compiles without any errors, one warning about an unused variable.

Cheers,
Dick Johnson

Penguin : Linux version 2.4.1 on an i686 machine (799.53 BogoMips).

    I was going to compile a list of innovations that could be
    attributed to Microsoft. Once I realized that Ctrl-Alt-Del
    was handled in the BIOS, I found that there aren't any.

Re: Simple LKM & copy_from_user question (followup)

[Randy.Dunlap]

Hi-

I'll suggest a few things for you.

    cd to your linux tree and 'make modules'
    Look at the gcc compile string there.
    Try to copy it closely.

I added -I/path/to/linux/include and -D__KERNEL__
and compiled your module with no problem.

If you had included the complete messages, we could have
seen that it was using /usr/include/linux for header files
instead of header files from linux/include/* .
(at least that's what it did on my system)

~Randy


David CM Weber wrote:
> 
> Attached is the file I"m having problems with.  I'm compiling it w/
> 
> gcc -O3 -c main.c
> 
> Thanks in advance,
> 
> Dave Weber
> Backbone Security, Inc.
> 570-422-7900
> 
> > -----Original Message-----
> > From: David CM Weber
> > Sent: Friday, July 20, 2001 12:45 PM
> > To: linux-kernel@vger.kernel.org
> > Subject: Simple LKM & copy_from_user question
> >
> >
> > Hello all.  I've been lurking for a while, and I have a quick
> > question.
> > I'm in the process of writing my first LKM to mess with the
> > sys_socketcall function.  I'm looking at the original one for
> > guidance,
> > and it makes a call to copy_from_user() to get some
> > socket-related data.
> >
> > So, to use copy_from_user(), I've gathered that I need to #include
> > <asm/uaccess.h>, so I do so.
> >
> > After including this file, I'm getting the following errors:
> >
> >
> > .../linux/timer.h:21: field 'vec' has incomplete type
> >
> > .../asm/uaccess.h::63: dereferencing pointer to incomplete type
> >
> >
> > (This is not a full list of the error message that it's reporting)
> >
> > Am I not setting a define correctly?
> >
> > I'm using Redhat 7.1, on an Intel P3 system.  It's the latest stable
> > release (2.4.x ??) of the kernel.
> >
> > If you need more information, please let me know.  This has been
> > troubling me for several days now..

Re: Simple LKM & copy_from_user question (followup)

[John Polyakov]

[-- Attachment #1: Type: text/plain, Size: 549 bytes --]

On Fri, 20 Jul 2001 16:26:43 -0400
"David CM Weber" <dweber@backbonesecurity.com> wrote:

DCW> Attached is the file I"m having problems with.  I'm compiling it w/ 

DCW> gcc -O3 -c main.c

DCW> Thanks in advance,

There is a Makefile for you in attachment.

Here is lsmod output:
It's work :)

[root@Sombre lkm]# lsmod
Module                  Size  Used by
main                     836   0  (unused)
NVdriver              660144  15  (autoclean)
[root@Sombre lkm]#


DCW> Dave Weber
DCW> Backbone Security, Inc.
DCW> 570-422-7900

---
WBR. //s0mbre

[-- Attachment #2: Makefile --]
[-- Type: text/plain, Size: 257 bytes --]

CC=gcc
MODCFLAGS := -Wall -Wwrite-strings -Wredundant-decls -O2 -DMODULE -D__KERNEL__ -DLINUX -I/usr/src/linux/include
MODCFLAGS1:= -O1 -D__KERNEL__ -DMODULE -Wall -DLINUX -I/usr/src/linux/include
main.o:      main.c
	        $(CC) $(MODCFLAGS1) -c main.c

RE: Simple LKM & copy_from_user question (followup)

[David CM Weber]

God(Allah, Ganesh, or whom/whatever) bless you all.  Turns out I am a
dumba** and forgot to define __KERNEL__

Thanks to all for your help.  It's a valuable lesson that I'm sure
newbies make lots of..

Thanks,


Dave Weber
(Feeling somewhat idiotic)

Backbone Security, Inc.
570-422-7900





> -----Original Message-----
> From: Randy.Dunlap [mailto:rddunlap@osdlab.org]
> Sent: Friday, July 20, 2001 4:39 PM
> To: David CM Weber
> Cc: linux-kernel@vger.kernel.org
> Subject: Re: Simple LKM & copy_from_user question (followup)
> 
> 
> Hi-
> 
> I'll suggest a few things for you.
> 
>     cd to your linux tree and 'make modules'
>     Look at the gcc compile string there.
>     Try to copy it closely.
> 
> I added -I/path/to/linux/include and -D__KERNEL__
> and compiled your module with no problem.
> 
> If you had included the complete messages, we could have
> seen that it was using /usr/include/linux for header files
> instead of header files from linux/include/* .
> (at least that's what it did on my system)
> 
> ~Randy
> 
> 
> David CM Weber wrote:
> > 
> > Attached is the file I"m having problems with.  I'm compiling it w/
> > 
> > gcc -O3 -c main.c
> > 
> > Thanks in advance,
> > 
> > Dave Weber
> > Backbone Security, Inc.
> > 570-422-7900
> > 
> > > -----Original Message-----
> > > From: David CM Weber
> > > Sent: Friday, July 20, 2001 12:45 PM
> > > To: linux-kernel@vger.kernel.org
> > > Subject: Simple LKM & copy_from_user question
> > >
> > >
> > > Hello all.  I've been lurking for a while, and I have a quick
> > > question.
> > > I'm in the process of writing my first LKM to mess with the
> > > sys_socketcall function.  I'm looking at the original one for
> > > guidance,
> > > and it makes a call to copy_from_user() to get some
> > > socket-related data.
> > >
> > > So, to use copy_from_user(), I've gathered that I need to #include
> > > <asm/uaccess.h>, so I do so.
> > >
> > > After including this file, I'm getting the following errors:
> > >
> > >
> > > .../linux/timer.h:21: field 'vec' has incomplete type
> > >
> > > .../asm/uaccess.h::63: dereferencing pointer to incomplete type
> > >
> > >
> > > (This is not a full list of the error message that it's reporting)
> > >
> > > Am I not setting a define correctly?
> > >
> > > I'm using Redhat 7.1, on an Intel P3 system.  It's the 
> latest stable
> > > release (2.4.x ??) of the kernel.
> > >
> > > If you need more information, please let me know.  This has been
> > > troubling me for several days now..
>