minix/kernel/ipc.h

   1 #ifndef IPC_H
   2 #define IPC_H
   3
   4 /* This header file defines constants for MINIX inter-process communication.
   5  * These definitions are used in the file proc.c.
   6  */
   7 #include <minix/com.h>
   8 #include <minix/ipcconst.h>
   9
  10 /* Masks and flags for system calls. */
  11 #define NON_BLOCKING    0x0080  /* do not block if target not ready */
  12 #define FROM_KERNEL     0x0100  /* message from kernel on behalf of a process */
  13
  14 #define WILLRECEIVE(src_e,dst_ptr,m_src_v,m_src_p) \
  15         ((RTS_ISSET(dst_ptr, RTS_RECEIVING) && \
  16         !RTS_ISSET(dst_ptr, RTS_SENDING)) && \
  17         CANRECEIVE(dst_ptr->p_getfrom_e,src_e,dst_ptr,m_src_v,m_src_p))
  18
  19 #define CANRECEIVE(receive_e,src_e,dst_ptr,m_src_v,m_src_p) \
  20         (((receive_e) == ANY || (receive_e) == (src_e)) && \
  21         (priv(dst_ptr)->s_ipcf == NULL || \
  22         allow_ipc_filtered_msg(dst_ptr,src_e,m_src_v,m_src_p)))
  23
  24 /* IPC status code macros. */
  25 #define IPC_STATUS_GET(p)       ((p)->p_reg.IPC_STATUS_REG)
  26 #define IPC_STATUS_CLEAR(p)     ((p)->p_reg.IPC_STATUS_REG = 0)
  27
  28 /*
  29  * XXX: the following check is used to set the status code only on RECEIVE.
  30  * SENDREC is not currently atomic for user processes. A process can return
  31  * from SENDREC in a different context than the original when a Posix signal
  32  * handler gets executed. For this reason, it is not safe to manipulate
  33  * the context (i.e. registers) when a process is blocked on a SENDREC.
  34  * Unfortunately, avoiding setting the status code for SENDREC doesn't solve
  35  * the problem entirely because in rare situations it is still necessary to
  36  * override retreg dynamically (and possibly in a different context).
  37  * A possible reliable solution is to improve our Posix signal handling
  38  * implementation and guarantee SENDREC atomicity w.r.t. the process context.
  39  */
  40 #define IPC_STATUS_ADD(p, m)    do { \
  41         if(!((p)->p_misc_flags & MF_REPLY_PEND)) { \
  42             (p)->p_reg.IPC_STATUS_REG |= (m); \
  43         } \
  44     } while(0)
  45 #define IPC_STATUS_ADD_CALL(p, call) \
  46     IPC_STATUS_ADD(p, IPC_STATUS_CALL_TO(call))
  47 #define IPC_STATUS_ADD_FLAGS(p, flags) \
  48     IPC_STATUS_ADD(p, IPC_STATUS_FLAGS(flags))
  49
  50 #endif /* IPC_H */