PROCESS_VM_READV(2)

NAME
	process_vm_readv, process_vm_writev - read/write from/to another 
	processes' address space.

SYNPOSIS
	#include <sys/uio.h>

	ssize_t process_vm_readv(pid_t pid, 
				 const struct iovec  *lvec, 
				 unsigned long liovcnt,
		 		 const struct iovec *rvec,
		 		 unsigned long riovcnt,
		 		 unsigned long flags);

	ssize_t process_vm_writev(pid_t pid, 
				  const struct iovec  *lvec, 
				  unsigned long liovcnt,
		 		  const struct iovec *rvec,
		 		  unsigned long riovcnt,
		 		  unsigned long flags);

DESCRIPTION
	The process_vm_readv() function reads from the memory locations
	described by riovcnt buffers from rvec in the process with PID of pid
	into liovcnt buffers described by lvec in the current process. 

	The process_vm_writev() function writes into the memory locations
	described by riovcnt buffers from rvec in the process with PID of pid
	into liovcnt buffers described by lvec in the current process. 

        The pointers lvec and rvec  point to an arrays of iovec structures,
	defined in <sys/uio.h> as:

           struct iovec {
               void  *iov_base;    /* Starting address */
               size_t iov_len;     /* Number of bytes to transfer */
           };

	Buffers are processed in array order. This means that the 
	process_vm_readv() function completely fills lvec[0] before proceeding
	to lvec[1], and so on. process_vm_readv() reads completely from rvec[0]
	before proceeding to rvec[1].

	Similarly the process_vm_writev() function writes out the entire
	contents of lvec[0] before proceeding to lvec[1]. And it completely
	fill revc[0] before proceeding to rvec[1].

	The lengths of rvec[i] and lvec[i] do not have to be the same.

	The data transfers of process_vm_readv and process_vm_writev are not
	guaranteed to be atomic.

	The flags parameter is currently unused and must be set to 0.

	In order to read or write from or to another process you must have
	the capability CAP_SYS_PTRACE or have the same uid and gid of target
	process. The permission required is exactly the same as that of being
	able to succesfully perform a ptrace wtih PTRACE_ATTACH on the target
	process.

RETURN VALUE
       On success process_vm_readv() function returns the number of bytes read;
       the process_vm_writev() function returns the number of bytes written. The
       On error, the number of bytes read or written is returned or -1 
       if it was unable to read/write any bytes and errno is set appropriately

ERRORS
	EINVAL The sum of the iov_len values of either lvec or rvec overflows
	       an ssize_t value

	EINVAL The value of the flags parameter is not 0

	EFAULT lvec or rvec is outside your accessible address space

	EFAULT the memory described by lvec is outside your accessible address
	       space

	EFAULT the memory described by rvec is outside the accessible address
	       space of process pid

	ENOMEM Out of memory

	EPERM  For the process_vm_readv() function you do not have permission 
	       to read from process pid

	EPERM  For the process_vm_writev() function you do not have permission 
	       to write to process pid

	ESRCH  THe pid does not exist


EXAMPLE
	The following code sample demonstrates the use of process_vm_readv().
	It reads 20 bytes at the address 0x10000 from the process with PID 10 
	and writes the first 10 bytes into buf1 and the second 10 bytes into
	buf2

  struct iovec local[2];
  struct iovec remote[1];
  unsigned long addr;
  unsigned long len;
  char buf1[10];
  char buf2[10];
  ssize_t nread;
  pid_t pid = 10; /* PID of target process */

  local[0].iov_base = buf1;
  local[0].iov_len = 10;
  local[1].iov_base = buf2;
  local[1].iov_len = 10;
  remote.iov_base = 0x10000;
  remote.iov_len = 20;

  nread = process_vm_readv(pid, local, 2, remote, 1, 0);
	

SEE ALSO
    readv(2), writev(2)