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.\" $FreeBSD: head/share/man/man9/proc_rwmem.9 291968 2015-12-07 22:08:12Z markj $
.\"
.Dd December 7, 2015
.Dt PROC_RWMEM 9
.Os
.Sh NAME
.Nm proc_rwmem ,
.Nm proc_readmem ,
.Nm proc_writemem
.Nd read from or write to a process address space
.Sh SYNOPSIS
.In sys/types.h
.In sys/ptrace.h
.Ft int
.Fn proc_rwmem "struct proc *p" "struct uio *uio"
.Ft ssize_t
.Fn proc_readmem "struct thread *td" "struct proc *p" "vm_offset_t va" "void *buf" "size_t len"
.Ft ssize_t
.Fn proc_writemem "struct thread *td" "struct proc *p" "vm_offset_t va" "void *buf" "size_t len"
.Sh DESCRIPTION
These functions are used to read to or write from the address space of the
process
.Fa p .
The
.Fn proc_rwmem
function requires the caller to specify the I/O parameters using a
.Vt "struct uio" ,
described in
.Xr uio 9 .
The
.Fn proc_readmem
and
.Fn proc_writemem
functions provide a simpler, less general interface which allows the caller to
read into or write the kernel buffer
.Fa buf
of size
.Fa len
from or to the memory at offset
.Fa va
in the address space of
.Fa p .
The operation is performed on behalf of thread
.Fa td ,
which will most often be the current thread.
.Pp
These functions may sleep and thus may not be called with any non-sleepable
locks held.
The process
.Fa p
must be held by the caller using
.Xr PHOLD 9 .
.Sh RETURN VALUES
The
.Fn proc_rwmem
function returns
.Dv 0
on success.
.Dv EFAULT
is returned if the specified user address is invalid, and
.Dv ENOMEM
is returned if the target pages could not be faulted in due to a resource
shortage.
.Pp
The
.Fn proc_readmem
and
.Fn proc_writemem
functions return the number of bytes read or written, respectively.
This may be smaller than the number of bytes requested, for example if the
request spans multiple pages in the process address space and one of them after
the first is not mapped.
Otherwise, -1 is returned.
.Sh SEE ALSO
.Xr copyin 9 ,
.Xr locking 9 ,
.Xr PHOLD 9 ,
.Xr uio 9
.Sh AUTHORS
This manual page was written by
.An Mark Johnston Aq Mt markj@FreeBSD.org .