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#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/fs.h>
#include <linux/miscdevice.h>
#include <linux/module.h>
#include <litmus/litmus.h>
/* only one page for now, but we might want to add a RO version at some point */
#define CTRL_NAME "litmus/ctrl"
/* allocate t->rt_param.ctrl_page*/
static int alloc_ctrl_page(struct task_struct *t)
{
int err = 0;
/* only allocate if the task doesn't have one yet */
if (!tsk_rt(t)->ctrl_page) {
tsk_rt(t)->ctrl_page = (void*) get_zeroed_page(GFP_KERNEL);
if (!tsk_rt(t)->ctrl_page)
err = -ENOMEM;
/* will get de-allocated in task teardown */
TRACE_TASK(t, "%s ctrl_page = %p\n", __FUNCTION__,
tsk_rt(t)->ctrl_page);
}
return err;
}
static int map_ctrl_page(struct task_struct *t, struct vm_area_struct* vma)
{
int err;
struct page* ctrl = virt_to_page(tsk_rt(t)->ctrl_page);
TRACE_CUR(CTRL_NAME
": mapping %p (pfn:%lx) to 0x%lx (prot:%lx)\n",
tsk_rt(t)->ctrl_page,page_to_pfn(ctrl), vma->vm_start,
vma->vm_page_prot);
/* Map it into the vma. */
err = vm_insert_page(vma, vma->vm_start, ctrl);
if (err)
TRACE_CUR(CTRL_NAME ": vm_insert_page() failed (%d)\n", err);
return err;
}
static void litmus_ctrl_vm_close(struct vm_area_struct* vma)
{
TRACE_CUR("%s flags=0x%x prot=0x%x\n", __FUNCTION__,
vma->vm_flags, vma->vm_page_prot);
TRACE_CUR(CTRL_NAME
": %p:%p vma:%p vma->vm_private_data:%p closed.\n",
(void*) vma->vm_start, (void*) vma->vm_end, vma,
vma->vm_private_data);
}
static int litmus_ctrl_vm_fault(struct vm_area_struct* vma,
struct vm_fault* vmf)
{
TRACE_CUR("%s flags=0x%x (off:%ld)\n", __FUNCTION__,
vma->vm_flags, vmf->pgoff);
/* This function should never be called, since all pages should have
* been mapped by mmap() already. */
WARN_ONCE(1, "Page faults should be impossible in the control page\n");
return VM_FAULT_SIGBUS;
}
static struct vm_operations_struct litmus_ctrl_vm_ops = {
.close = litmus_ctrl_vm_close,
.fault = litmus_ctrl_vm_fault,
};
static int litmus_ctrl_mmap(struct file* filp, struct vm_area_struct* vma)
{
int err = 0;
/* first make sure mapper knows what he's doing */
/* you can only get one page */
if (vma->vm_end - vma->vm_start != PAGE_SIZE)
return -EINVAL;
/* you can only map the "first" page */
if (vma->vm_pgoff != 0)
return -EINVAL;
/* you can't share it with anyone */
if (vma->vm_flags & (VM_MAYSHARE | VM_SHARED))
return -EINVAL;
vma->vm_ops = &litmus_ctrl_vm_ops;
/* This mapping should not be kept across forks,
* cannot be expanded, and is not a "normal" page. */
vma->vm_flags |= VM_DONTCOPY | VM_DONTEXPAND | VM_IO;
/* We don't want the first write access to trigger a "minor" page fault
* to mark the page as dirty. This is transient, private memory, we
* don't care if it was touched or not. __S011 means RW access, but not
* execute, and avoids copy-on-write behavior.
* See protection_map in mmap.c. */
vma->vm_page_prot = __S011;
err = alloc_ctrl_page(current);
if (!err)
err = map_ctrl_page(current, vma);
TRACE_CUR("%s flags=0x%x prot=0x%lx\n",
__FUNCTION__, vma->vm_flags, vma->vm_page_prot);
return err;
}
static struct file_operations litmus_ctrl_fops = {
.owner = THIS_MODULE,
.mmap = litmus_ctrl_mmap,
};
static struct miscdevice litmus_ctrl_dev = {
.name = CTRL_NAME,
.minor = MISC_DYNAMIC_MINOR,
.fops = &litmus_ctrl_fops,
};
static int __init init_litmus_ctrl_dev(void)
{
int err;
BUILD_BUG_ON(sizeof(struct control_page) > PAGE_SIZE);
printk("Initializing LITMUS^RT control device.\n");
err = misc_register(&litmus_ctrl_dev);
if (err)
printk("Could not allocate %s device (%d).\n", CTRL_NAME, err);
return err;
}
static void __exit exit_litmus_ctrl_dev(void)
{
misc_deregister(&litmus_ctrl_dev);
}
module_init(init_litmus_ctrl_dev);
module_exit(exit_litmus_ctrl_dev);
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