NAME

       cacheflush - flush contents of instruction and/or data cache

SYNOPSIS

       #include <asm/cachectl.h>

       int cacheflush(char *addr, 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 or -1 on error.  If errors are detected, errno will 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).

CONFORMING TO

       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 version 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.

COLOPHON

       This  page  is  part  of  release  5.10  of  the  Linux man-pages project.  A description of the project,
       information  about  reporting  bugs,  and  the  latest  version  of  this   page,   can   be   found   at
       https://www.kernel.org/doc/man-pages/.

Linux                                              2020-12-21                                      CACHEFLUSH(2)