minix/drivers/log/liveupdate.c
David van Moolenbroek c51cd5fe91 Server/driver protocols: no longer allow third-party copies.
Before safecopies, the IO_ENDPT and DL_ENDPT message fields were needed
to know which actual process to copy data from/to, as that process may
not always be the caller. Now that we have full safecopy support, these
fields have become useless for that purpose: the owner of the grant is
*always* the caller. Allowing the caller to supply another endpoint is
in fact dangerous, because the callee may then end up using a grant
from a third party. One could call this a variant of the confused
deputy problem.

From now on, safecopy calls should always use the caller's endpoint as
grant owner. This fully obsoletes the DL_ENDPT field in the
inet/ethernet protocol. IO_ENDPT has other uses besides identifying the
grant owner though. This patch renames IO_ENDPT to USER_ENDPT, not only
because that is a more fitting name (it should never be used for I/O
after all), but also in order to intentionally break any old system
source code outside the base system. If this patch breaks your code,
fixing it is fairly simple:

- DL_ENDPT should be replaced with m_source;
- IO_ENDPT should be replaced with m_source when used for safecopies;
- IO_ENDPT should be replaced with USER_ENDPT for any other use, e.g.
  when setting REP_ENDPT, matching requests in CANCEL calls, getting
  DEV_SELECT flags, and retrieving of the real user process's endpoint
  in DEV_OPEN.

The changes in this patch are binary backward compatible.
2011-04-11 17:35:05 +00:00

99 lines
3.2 KiB
C

#include "log.h"
/* State management variables. */
#define NR_DEVS 1 /* number of minor devices */
EXTERN struct logdevice logdevices[NR_DEVS];
/* State management helpers. */
PRIVATE int is_read_pending;
PRIVATE int is_select_callback_pending;
PRIVATE void load_state_info(void)
{
int i, found_pending;
struct logdevice *log;
/* Check if reads or select callbacks are pending. */
is_read_pending = FALSE;
is_select_callback_pending = FALSE;
found_pending = FALSE;
for (i = 0; i < NR_DEVS && !found_pending; i++) {
log = &logdevices[i];
if(log->log_source != NONE) {
is_read_pending = TRUE;
}
if(log->log_selected) {
is_select_callback_pending = TRUE;
}
found_pending = (is_read_pending && is_select_callback_pending);
}
}
/* Custom states definition. */
#define LOG_STATE_SELECT_PROTOCOL_FREE (SEF_LU_STATE_CUSTOM_BASE + 0)
#define LOG_STATE_IS_CUSTOM(s) ((s) == LOG_STATE_SELECT_PROTOCOL_FREE)
/*===========================================================================*
* sef_cb_lu_prepare *
*===========================================================================*/
PUBLIC int sef_cb_lu_prepare(int state)
{
int is_ready;
/* Load state information. */
load_state_info();
/* Check if we are ready for the target state. */
is_ready = FALSE;
switch(state) {
/* Standard states. */
case SEF_LU_STATE_REQUEST_FREE:
is_ready = (!is_read_pending);
break;
case SEF_LU_STATE_PROTOCOL_FREE:
is_ready = (!is_read_pending && !is_select_callback_pending);
break;
/* Custom states. */
case LOG_STATE_SELECT_PROTOCOL_FREE:
is_ready = (!is_select_callback_pending);
break;
}
/* Tell SEF if we are ready. */
return is_ready ? OK : ENOTREADY;
}
/*===========================================================================*
* sef_cb_lu_state_isvalid *
*===========================================================================*/
PUBLIC int sef_cb_lu_state_isvalid(int state)
{
return SEF_LU_STATE_IS_STANDARD(state) || LOG_STATE_IS_CUSTOM(state);
}
/*===========================================================================*
* sef_cb_lu_state_dump *
*===========================================================================*/
PUBLIC void sef_cb_lu_state_dump(int state)
{
/* Load state information. */
load_state_info();
sef_lu_dprint("log: live update state = %d\n", state);
sef_lu_dprint("log: is_read_pending = %d\n", is_read_pending);
sef_lu_dprint("log: is_select_callback_pending = %d\n",
is_select_callback_pending);
sef_lu_dprint("log: SEF_LU_STATE_WORK_FREE(%d) reached = %d\n",
SEF_LU_STATE_WORK_FREE, TRUE);
sef_lu_dprint("log: SEF_LU_STATE_REQUEST_FREE(%d) reached = %d\n",
SEF_LU_STATE_REQUEST_FREE, (!is_read_pending));
sef_lu_dprint("log: SEF_LU_STATE_PROTOCOL_FREE(%d) reached = %d\n",
SEF_LU_STATE_PROTOCOL_FREE, (!is_read_pending
&& !is_select_callback_pending));
sef_lu_dprint("log: LOG_STATE_SELECT_PROTOCOL_FREE(%d) reached = %d\n",
LOG_STATE_SELECT_PROTOCOL_FREE, (!is_select_callback_pending));
}