sys/cache.3

   1 .Dd September 21, 2006
   2 .Dt CACHE 3
   3 .Os Darwin
   4 .Sh NAME
   5 .Nm sys_cache_control ,
   6 .Nm sys_icache_invalidate ,
   7 .Nm sys_dcache_flush
   8 .Nd cache control
   9 .Sh LIBRARY
  10 .Lb libc
  11 .Sh SYNOPSIS
  12 .In libkern/OSCacheControl.h
  13 .Ft int
  14 .Fn sys_cache_control "int function" "void *start" "size_t len"
  15 .Ft void
  16 .Fn sys_icache_invalidate "void *start" "size_t len"
  17 .Ft void
  18 .Fn sys_dcache_flush "void *start" "size_t len"
  19 .Sh DESCRIPTION
  20 .Pp
  21 These functions operate on every cache line containing one of the
  22 .Fa len
  23 bytes of memory pointed to by
  24 .Fa start .
  25 Normally the operations apply to every
  26 processor in the system, but the exact semantics of these
  27 operations is platform dependent.  They should be used with caution.
  28 .Pp
  29 .Fn sys_cache_control
  30 performs the operation specified by
  31 .Fa function .
  32 Refer to the header file for a list of currently supported functions.
  33 .Pp
  34 .Fn sys_icache_invalidate
  35 prepares memory for execution, typically by invalidating the instruction
  36 cache for the indicated range.  This should be called
  37 after writing machine instructions to memory, and before
  38 executing them.  On IA32 processors this function is a NOP, because
  39 their instruction caches are coherent.
  40 .Pp
  41 .Fn sys_dcache_flush
  42 writes modified data cache lines to main memory,
  43 and then invalidates all lines in the range being operated on.
  44 It can be useful when dealing with cache incoherent
  45 devices or DMA.
  46 .Sh RETURN VALUES
  47 .Fn sys_cache_control
  48 returns zero on success, ENOTSUP if
  49 .Fa function
  50 is not valid.
  51 .Sh SEE ALSO
  52 .Xr atomic 3 ,
  53 .Xr barrier 3
  54 .Sh HISTORY
  55 These functions first appeared in Mac OS 10.5 (Leopard).