Orion

/*
 * This file handles safely getting data from userspace for the Kernel.  This is
 * for security reasons to prevent the user from tricking a syscall into
 * manipulating/leaking Kernel data structures.  User memory is defined as any
 * address range that completely sits in a Virtual Memory Region.
 */

#include <stdint.h>
#include <string.h>
#include "vm.h"
#include "../task/task.h"

/* User can read this address */
int
verify_access(const void *addr, size_t len, int prot)
{
	if (!in_syscall() || !addr || !len)
		return 1;

	/* Iterate all user memory regions */
	VMRegion *head;
	for (head = current->vm->regions; head; head = head->next) {
		if ((uintptr_t) addr >= head->start
		 && ((uintptr_t) addr + len) < head->end)
			break;
	}
	if (!head) {
		head = current->stack;
		if ((uintptr_t) addr < head->start
		 || ((uintptr_t) addr + len) >= head->end)
			head = NULL;
	}
	/* No fitting region */
	if (!head)
		return 0;
	return (head->prot & prot);
}