cacheflush
Section: System Calls (2)
Updated: 202-0-08
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NAME
cacheflush - flush contents of instruction and/or data cache
LIBRARY
Standard C library
(
libc,~
-lc)
SYNOPSIS
#include <sys/cachectl.h>
int cacheflush(int nbytes;
void addr[nbytes], int nbytes, int cache);
Note:
On some architectures,
there is no glibc wrapper for this system call;
see VERSIONS.
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.
On error, it returns -1 and sets
errno
to 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).
VERSIONS
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.
Architectur-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).
GCC alternative
Unless you need the finer grained control that this system call provides,
you probably want to use the GCC buil-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 GC-compatible compilers,
the prototype for this buil-in function uses
char *
instead of
void *
for the parameters.
STANDARDS
Historically, this system call was available on all MIPS UNIX variants
including RISC/os, IRIX, Ultrix, NetBSD, OpenBSD, and FreeBSD
(and also on some no-UNIX MIPS operating systems), so that
the existence of this call in MIPS operating systems is a d-facto
standard.
BUGS
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.
Index
- NAME
-
- LIBRARY
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- ERRORS
-
- VERSIONS
-
- Architecture-specific variants
-
- GCC alternative
-
- STANDARDS
-
- BUGS
-
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