2008/12/23 Gerry Weaver <ger...@compvia.com>
> Hello All,
>
> I am working on a driver that collects various network statistics via pfil.
> I have a simple array of structures that I use to store the statistics. I
> also have a user space process that needs to collect these statistics every
> second or so. A copy operation from kernel to user space would be too
> expensive. Is there a mechanism that would allow me to gain direct access to
> my kernel array from user space? The user process would only need read
> access. It seems like maybe this could be done with mmap, but since this is
> not a character driver, there is no device file etc.. I'm a newbie, so I
> apologize if this is something that should be obvious.
>
>
> Thanks in advance,
> Gerry
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>
Hi,
some times ago I solve this task. That's my solution in a system call
(whithout cdev).
Thanx in advance for founded mistakes and possible bugs (-:
#include <sys/param.h>
#include <sys/proc.h>
#include <sys/conf.h>
#include <sys/module.h>
#include <sys/sysent.h>
#include <sys/kernel.h>
#include <sys/systm.h>
#include <sys/sysproto.h>
#include <sys/resourcevar.h>
#include <vm/vm.h>
#include <vm/pmap.h>
#include <vm/vm_map.h>
#include <vm/vm_param.h>
#include <vm/vm_kern.h>
#include <vm/vm_object.h>
/* Arguments for syscall */
struct args {
/* Pointer to allocated Buffer */
unsigned int *p;
};
/* String to be located in maped buffer */
const char *str = "BSD IS SEXY";
/* Syscall func */
static int
syscf(struct thread *td, void *sa)
{
int error;
struct args *uap;
vm_offset_t addr; /* Kernel space address */
vm_offset_t user_addr; /* User space address */
struct proc *procp = (struct proc *)td->td_proc;
struct vmspace *vms = procp->p_vmspace;
uap = (struct args *)sa;
PROC_LOCK(procp);
user_addr = round_page((vm_offset_t)vms->vm_daddr +
lim_max(procp, RLIMIT_DATA));
PROC_UNLOCK(procp);
MALLOC(addr, vm_offset_t, PAGE_SIZE, M_DEVBUF, M_WAITOK | M_ZERO);
vm_map_entry_t myentry;
vm_object_t myobject;
vm_pindex_t mypindex;
vm_prot_t myprot;
boolean_t mywired;
vm_ooffset_t objoffset;
vm_map_lookup(&kmem_map, addr, VM_PROT_ALL,
&myentry, &myobject, &mypindex, &myprot, &mywired);
/* OUT */
vm_map_lookup_done(kmem_map, myentry);
printf("---> Syscall: hint for allocating space = 0x%X\n", addr);
if (myobject == kmem_object){
printf("---> Syscall: Yes, it is kmem_obj! \n");
}
/* Offset in vm_object */
objoffset = addr - myentry->start + myentry->offset;
printf("------> Syscall: Object offset = 0x%X \n", (unsigned
int)objoffset);
/*
* Try to map kernel buffer to user space
*/
vm_object_reference(myobject); /* NEEDED Increment vm_obj references
*/
error = vm_map_find(&vms->vm_map, myobject, objoffset, (vm_offset_t
*)&user_addr,
PAGE_SIZE, TRUE, VM_PROT_RW, VM_PROT_RW,
MAP_ENTRY_NOFAULT);
if (error == KERN_SUCCESS) {
/* copy string using kernel address */
size_t len;
copystr(str, (void *)addr, 12, &len);
/*
* Tell to user process it's user space address
*/
*uap->p = user_addr;
/*
* Try to read the string using user space address
*/
printf("String: %s\n", (char *)*uap->p);
printf("---> Syscall: user_addr for allocating space =
0x%X\n", user_addr);
}
return (0);
}
/* Sysent entity for syscall */
static struct sysent sc_sysent = {
1, /* Number of
arguments */
syscf /* Syscall function */
};
/* Offset in sysent[] */
static int offset = NO_SYSCALL;
/* Loader */
static int
load (struct module *m, int cmd, void *something)
{
int error = 0;
switch(cmd){
case MOD_LOAD:
printf("Module with sysc loaded. Offset = %d \n",
offset);
break;
case MOD_UNLOAD:
printf("Module with sysc unloaded. Offset = %d \n",
offset);
break;
default:
error = EOPNOTSUPP;
break;
}
return (error);
}
/* Syscall macro*/
SYSCALL_MODULE(fiveg_sysc, &offset, &sc_sysent, load, NULL);
If needed, I can post user space program.
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