cacheflush(2) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | CONFORMING TO | NOTES | BUGS | COLOPHON

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

NAME         top

       cacheflush - flush contents of instruction and/or data cache

SYNOPSIS         top

       #include <sys/cachectl.h>

       int cacheflush(void *addr, int nbytes, int cache);

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

DESCRIPTION         top

       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         top

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

ERRORS         top

       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         top

       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         top

   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         top

       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         top

       This page is part of release 5.11 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                          2021-03-22                  CACHEFLUSH(2)

Pages that refer to this page: syscalls(2)