cacheflush(2) - Linux manual page (original) (raw)

cacheflush(2) System Calls Manual cacheflush(2)

NAME top

   cacheflush - flush contents of instruction and/or data cache

LIBRARY top

   Standard C library (_libc_, _-lc_)

SYNOPSIS top

   **#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 VERSIONS.

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](../man3/errno.3.html)_ 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).

VERSIONS top

   **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** _size_**);**

   SH:
          **int cacheflush(unsigned long** _addr_**, unsigned long** _size_**, 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)](../man2/syscall.2.html).

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 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.

BUGS top

   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.

COLOPHON top

   This page is part of the _man-pages_ (Linux kernel and C library
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   man-pages@man7.org

Linux man-pages 6.10 2024-11-17 cacheflush(2)

Pages that refer to this page:syscalls(2)