---
name: "useracc"
section: "9"
platform: "freebsd"
package: "base"
version: "16.0-CURRENT-20261027-61c70dc16a79"
release: "FreeBSD 16.0-CURRENT (2026-10-27)"
platforms: ["linux", "freebsd"]
url: "https://new.carta.tech/kernacc"
---

# useracc(9)

check memory regions for accessibility

Part of [kernacc(9)](/kernacc/9.md).

## NAME

**kernacc**, **useracc** – check memory regions for accessibility

## SYNOPSIS

**#include \<sys/param.h\>**

**#include \<sys/proc.h\>**

**#include \<vm/vm.h\>**

**#include \<vm/vm\_extern.h\>**

*int*\

**kernacc**(*void \*addr*, *int len*, *int rw*);

*int*\

**useracc**(*void \*addr*, *int len*, *int rw*);

## DESCRIPTION

The **kernacc**() and **useracc**() functions check whether operations of the type specified in *rw* are permitted in the range of virtual addresses given by *addr* and *len*. The possible values of *rw* are any bitwise combination of VM\_PROT\_READ, VM\_PROT\_WRITE and VM\_PROT\_EXECUTE. **kernacc**() checks addresses in the kernel address space, while **useracc**() considers *addr* to represent an user space address. The process context to use for this operation is taken from the global variable *curproc*.

## RETURN VALUES

Both functions return boolean true if the type of access specified by *rw* is permitted. Otherwise boolean false is returned.

## BUGS

The process pointer should be passed in as an argument to **useracc**().