cacheflush

CACHEFLUSH(2)              Linux Programmer's Manual             CACHEFLUSH(2)

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 de-
       tected, 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 nowa-
       days, Linux provides a cacheflush() system call on some other architec-
       tures, 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 dif-
       ferent 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 pro-
       vides,  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  ar-
       guments,  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)