do_copy.c

Minix3.11的源码。[MINIX 3是一个为高可靠性应用而设计的自由且简洁的类UNIX系统。]

/* The kernel call implemented in this file:
 *   m_type:	SYS_VIRCOPY, SYS_PHYSCOPY
 *
 * The parameters for this kernel call are:
 *    m5_c1:	CP_SRC_SPACE		source virtual segment
 *    m5_l1:	CP_SRC_ADDR		source offset within segment
 *    m5_i1:	CP_SRC_PROC_NR		source process number
 *    m5_c2:	CP_DST_SPACE		destination virtual segment
 *    m5_l2:	CP_DST_ADDR		destination offset within segment
 *    m5_i2:	CP_DST_PROC_NR		destination process number
 *    m5_l3:	CP_NR_BYTES		number of bytes to copy
 */

#include "../system.h"
#include <minix/type.h>

#if (USE_VIRCOPY || USE_PHYSCOPY)

/*===========================================================================*
 *				do_copy					     *
 *===========================================================================*/
PUBLIC int do_copy(m_ptr)
register message *m_ptr;	/* pointer to request message */
{
/* Handle sys_vircopy() and sys_physcopy().  Copy data using virtual or
 * physical addressing. Although a single handler function is used, there 
 * are two different kernel calls so that permissions can be checked. 
 */
  struct vir_addr vir_addr[2];	/* virtual source and destination address */
  phys_bytes bytes;		/* number of bytes to copy */
  int i;

  /* Dismember the command message. */
  vir_addr[_SRC_].proc_nr = m_ptr->CP_SRC_PROC_NR;
  vir_addr[_SRC_].segment = m_ptr->CP_SRC_SPACE;
  vir_addr[_SRC_].offset = (vir_bytes) m_ptr->CP_SRC_ADDR;
  vir_addr[_DST_].proc_nr = m_ptr->CP_DST_PROC_NR;
  vir_addr[_DST_].segment = m_ptr->CP_DST_SPACE;
  vir_addr[_DST_].offset = (vir_bytes) m_ptr->CP_DST_ADDR;
  bytes = (phys_bytes) m_ptr->CP_NR_BYTES;

  /* Now do some checks for both the source and destination virtual address.
   * This is done once for _SRC_, then once for _DST_. 
   */
  for (i=_SRC_; i<=_DST_; i++) {

      /* Check if process number was given implictly with SELF and is valid. */
      if (vir_addr[i].proc_nr == SELF) vir_addr[i].proc_nr = m_ptr->m_source;
      if (! isokprocn(vir_addr[i].proc_nr) && vir_addr[i].segment != PHYS_SEG) 
          return(EINVAL); 

      /* Check if physical addressing is used without SYS_PHYSCOPY. */
      if ((vir_addr[i].segment & PHYS_SEG) &&
          m_ptr->m_type != SYS_PHYSCOPY) return(EPERM);
  }

  /* Check for overflow. This would happen for 64K segments and 16-bit 
   * vir_bytes. Especially copying by the PM on do_fork() is affected. 
   */
  if (bytes != (vir_bytes) bytes) return(E2BIG);

  /* Now try to make the actual virtual copy. */
  return( virtual_copy(&vir_addr[_SRC_], &vir_addr[_DST_], bytes) );
}
#endif /* (USE_VIRCOPY || USE_PHYSCOPY) */