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
       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)