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     proc_rwmem, proc_readmem, proc_writemem — read from or write to a process address space


     #include <sys/types.h>
     #include <sys/ptrace.h>

     proc_rwmem(struct proc *p, struct uio *uio);

     proc_readmem(struct thread *td, struct proc *p, vm_offset_t va, void *buf, size_t len);

     proc_writemem(struct thread *td, struct proc *p, vm_offset_t va, void *buf, size_t len);


     These functions are used to read to or write from the address space of the process p.  The
     proc_rwmem() function requires the caller to specify the I/O parameters using a struct uio,
     described in uio(9).  The proc_readmem() and proc_writemem() functions provide a simpler,
     less general interface which allows the caller to read into or write the kernel buffer buf
     of size len from or to the memory at offset va in the address space of p.  The operation is
     performed on behalf of thread td, which will most often be the current thread.

     These functions may sleep and thus may not be called with any non-sleepable locks held.  The
     process p must be held by the caller using PHOLD(9).


     The proc_rwmem() function returns 0 on success.  EFAULT is returned if the specified user
     address is invalid, and ENOMEM is returned if the target pages could not be faulted in due
     to a resource shortage.

     The proc_readmem() and 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.


     copyin(9), locking(9), PHOLD(9), uio(9)


     This manual page was written by Mark Johnston <>.