cacheflush - flush contents of instruction and/or data cache
int cacheflush(void *addr, int nbytes, int cache);
Note: On some architectures, there is no glibc wrapper for
this system call; see NOTES.
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:
cacheflush() returns 0 on success. On error, it returns -1 and sets
errno to indicate the error.
- Flush the instruction cache.
- Write back to memory and invalidate the affected valid cache lines.
- Same as (ICACHE|DCACHE).
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.
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.
Glibc provides a wrapper for this system call, with the prototype shown in
SYNOPSIS, for the following architectures: ARC, CSKY, MIPS, and NIOS2.
- Some or all of the address range addr to (addr+nbytes-1) is
- cache is not one of ICACHE, DCACHE, or BCACHE
(but see BUGS).
On some other architectures, Linux provides this system call, with
int cacheflush(unsigned long addr, int scope, int cache,
unsigned long len);
int cacheflush(unsigned long addr, unsigned long len, int op);
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).
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
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
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