NAME

       cacheflush - flush contents of instruction and/or data cache

LIBRARY

       Standard C library (libc, -lc)

SYNOPSIS

       #include <sys/cachectl.h>

       int cacheflush(void addr[.nbytes], int nbytes, int cache);

       Note: On some architectures, there is no glibc wrapper for this system call; see NOTES.

DESCRIPTION

       cacheflush()  flushes the contents of the indicated cache(s) for the user addresses in the
       range addr to (addr+nbytes-1).  cache may be one of:

       ICACHE Flush the instruction cache.

       DCACHE Write back to memory and invalidate the affected valid cache lines.

       BCACHE Same as (ICACHE|DCACHE).

RETURN VALUE

       cacheflush() returns 0 on success.  On error, it returns -1 and sets errno to indicate the
       error.

ERRORS

       EFAULT Some or all of the address range addr to (addr+nbytes-1) is not accessible.

       EINVAL cache is not one of ICACHE, DCACHE, or BCACHE (but see BUGS).

STANDARDS

       Historically,  this system call was available on all MIPS UNIX variants including RISC/os,
       IRIX, Ultrix, NetBSD, OpenBSD, and FreeBSD (and  also  on  some  non-UNIX  MIPS  operating
       systems),  so  that  the  existence  of  this call in MIPS operating systems is a de-facto
       standard.

   Caveat
       cacheflush() should not be used in programs intended to be portable.  On Linux, this  call
       first  appeared  on  the  MIPS  architecture,  but nowadays, Linux provides a cacheflush()
       system call on some other architectures, but with different arguments.

NOTES

   Architecture-specific variants
       glibc provides a wrapper for this system call, with the prototype shown in  SYNOPSIS,  for
       the following architectures: ARC, CSKY, MIPS, and NIOS2.

       On some other architectures, Linux provides this system call, with different arguments:

       M68K:
              int cacheflush(unsigned long addr, int scope, int cache,
                             unsigned long len);

       SH:
              int cacheflush(unsigned long addr, unsigned long len, int op);

       NDS32:
              int cacheflush(unsigned int start, unsigned int end, int cache);

       On the above architectures, glibc does not provide a wrapper for this system call; call it
       using syscall(2).

   GCC alternative
       Unless you need the finer grained control that this system  call  provides,  you  probably
       want to use the GCC built-in function __builtin___clear_cache(), which provides a portable
       interface across platforms supported by GCC and compatible compilers:

           void __builtin___clear_cache(void *begin, void *end);

       On platforms that don't require instruction cache flushes,  __builtin___clear_cache()  has
       no effect.

       Note: On some GCC-compatible compilers, the prototype for this built-in function uses char
       * instead of void * for the parameters.

BUGS

       Linux kernels older than Linux 2.6.11 ignore the addr and nbytes  arguments,  making  this
       function fairly expensive.  Therefore, the whole cache is always flushed.

       This  function always behaves as if BCACHE has been passed for the cache argument and does
       not do any error checking on the cache argument.