[Schemix-devel] Using AVCALL library to call random functions in the kernel

[Cory Cross]

Hello everyone (anyone?),
    I stopped working on this a while ago after getting dead-locked on a
foreign-function-interface library but remained interested. I ran across
AVCALL many months ago and finally decided to make it work. I tried
libffi, but it has many userland dependencies.

Progress: Got compilation and primitive function of avcall.
Next steps: Bring in vacall. Make both access any given function in the
kernel. Integrate into Schemix's kernel-lambda. (Of course, I still need
to locate my old Schemix files somewhere...)

My steps:
1. Download attached files and place in separate directory mod-avcall
2. Download ffcall (I used version 1.10) and compile avcall
3. From avcall directory, copy avcall.h and .libs/libavcall.a to mod-avcall
4. Run "make" in mod-avcall
5. I added "V=1" to the Makefile for verbosity. The last thing "make"
does is link cory.o and cory.mod.o to create cory.ko. Copy this command,
then add "libavcall.a" to the end, in effect linking cory.o, cory.mod.o,
and libavcall.a to create a kernel module "cory.ko"

Cory Cross

#include <linux/module.h>
#include <linux/kernel.h>
#include "avcall.h"

static void cory_print( char* text ) {
  printk( KERN_ALERT "%s\n", text );
}

static int __init cory_init(void)
{
        char string[60] = "FFI works!";
        av_alist function_list;

        printk(KERN_ALERT "Hello, world\n");

        av_start_void( function_list, cory_print );
        av_ptr( function_list, char*, string );
        av_call( function_list );


        return 0;
}

static void __exit cory_exit(void)
{
  //    printk(KERN_ALERT "Da symbol:%lu\n",(unsigned long) __get_any_symbol( 
"donuttin" ) );
        printk(KERN_ALERT "Goodbye, world\n");
}

module_init(cory_init);
module_exit(cory_exit);
MODULE_LICENSE("GPL");

#MODULE := cory.ko

OBJS := cory.o libavcall.a

obj-m   := cory.o

#CFLAGS += -E
LDFLAGS = -v

all:
        make -C /lib/modules/$(shell uname -r)/build M=$(PWD) V=1 modules

clean:
        make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean