Nucleus

/*
 * 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 <nucleus/memory.h>
#include <nucleus/task.h>
#include "namespace.h"

VMRegion *find_region(uintptr_t addr);

/* Check if user has access to a region of memory */
int
verify_access(const void *addr, size_t len, int prot)
{
	if (!len || !(current && current->inSyscall))
		return 1;

	VMRegion *region;
	int minprot = ~0;
	uintptr_t end = (uintptr_t) addr;
	do {
		region = find_region(end);
		if (!region)
			return 0;
		minprot &= region->prot;
		end = region->end;
	} while (end < (uintptr_t) addr + len);
	return (minprot & prot);
}