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).

VERSIONS

       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.

   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.

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.

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.