Hi !
trying to write up a simple mmap for a pseudo device that accesses a
kmalloc'ed area.
The driver is a character driver that only has mmap implemented - the kmalloc
is done in init module and the pointer to the buffer is in global context.
I expected to be able to write to the mmap'ed area from user-space but it
never shows up in kernel space (the printk in driver_mmap always shows the
init_msg passed in init_module).
the basic framework I'm using is below - can anybody point me to an obvious
error or to some docs that would explain how to share an kmalloc'ed area
with user-space via mmap ?
thx !
hofrat
---driver---
char *kmalloc_area;
...
static int
driver_mmap(struct file *file,
struct vm_area_struct *vma)
{
vma->vm_flags |= VM_LOCKED|VM_SHARED;
printk("message buffer: %s\",kmalloc_area);
remap_page_range(vma->vm_start,
virt_to_phys(kmalloc_area),
LEN,
PAGE_SHARED);
return 0;
}
static struct file_operations simple_fops={
mmap: driver_mmap,
};
int
init_module(void){
...
kmalloc_area=kmalloc(LEN,GFP_USER);
strncpy(kmalloc_area,init_msg,sizeof(init_msg));
...
}
---user-app---
int main(void)
{
int fd;
char msg[]="some message - should appear in kernel space";
unsigned int *addr;
if((fd=open("/dev/simple-device", O_RDWR))<0)
addr = mmap(0, LEN, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
memset(addr,0,LEN);
strncpy(addr,msg,sizeof(msg));
return 0;
}
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Mon Sep 30 2002 - 22:00:18 EST