sync_instruction_memory(3C)

NAME

     sync_instruction_memory - make modified instructions execut-
     able

SYNOPSIS

     void sync_instruction_memory(caddr_t addr, int len);

DESCRIPTION

     The  sync_instruction_memory()  function  performs  whatever
     steps  are  required to make instructions modified by a pro-
     gram executable.

     Some processor architectures, including some  SPARC  proces-
     sors,  have  separate  and  independent instruction and data
     caches which are not kept consistent by hardware.  For exam-
     ple,  if  the instruction cache contains an instruction from
     some address and the program then stores a  new  instruction
     at  that address, the new instruction may not be immediately
     visible to the instruction fetch  mechanism.  Software  must
     explicitly  invalidate the instruction cache entries for new
     or changed mappings of pages that might  contain  executable
     instructions.   The  sync_instruction_memory() function per-
     forms this function, and/or any other  functions  needed  to
     make  modified  instructions between addr and addr+len visi-
     ble. A program should call  sync_instruction_memory()  after
     modifying instructions and before executing them.

     On processors  with  unified  caches  (one  cache  for  both
     instructions  and data) and pipelines which are flushed by a
     branch instruction, such as the x86 architecture, the  func-
     tion may do nothing and just return.

     The changes are immediately visible to  the  thread  calling
     sync_instruction_memory() when the call returns, even if the
     thread should migrate to another processor during  or  after
     the call. The changes become visible to other threads in the
     same manner that stores do; that is, they eventually  become
     visible, but the latency is implementation-dependent.

     The  result  of  executing   sync_instruction_memory()   are
     unpredictable  if  addr through addr+len-1 are not valid for
     the address space of the program making the call.

RETURN VALUES

     No values are returned.

ATTRIBUTES

     See attributes(5) for descriptions of the  following  attri-
     butes:

     ____________________________________________________________
    |       ATTRIBUTE TYPE        |       ATTRIBUTE VALUE       |
    |_____________________________|_____________________________|
    | MT-Level                    | MT-Safe                     |
    |_____________________________|_____________________________|

SEE ALSO

     attributes(5)