SYNC_INSTRUCTION_MEMORY(3C) Standard C Library Functions

NAME

sync_instruction_memory - make modified instructions executable

SYNOPSIS

void sync_instruction_memory(caddr_t addr, int len);

DESCRIPTION

The sync_instruction_memory() function performs whatever steps are
required to make instructions modified by a program executable.


Some processor architectures, including some SPARC processors, have
separate and independent instruction and data caches which are not kept
consistent by hardware. For example, if the instruction cache contains
an instruction from some address and the program then stores a new
instruction at that address, the new instruction may not be immediately
visible to the instruction fetch mechanism. Software must explicitly
invalidate the instruction cache entries for new or changed mappings of
pages that might contain executable instructions. The
sync_instruction_memory() function performs this function, and/or any
other functions needed to make modified instructions between addr and
addr+len visible. A program should call sync_instruction_memory() after
modifying instructions and before executing them.


On processors with unified caches (one cache for both instructions and
data) and pipelines which are flushed by a branch instruction, such as
the x86 architecture, the function may do nothing and just return.


The changes are immediately visible to the thread calling
sync_instruction_memory() when the call returns, even if the thread
should migrate to another processor during or after the call. The changes
become visible to other threads in the same manner that stores do; that
is, they eventually become visible, but the latency is implementation-
dependent.


The result of executing sync_instruction_memory() are unpredictable if
addr through addr+len-1 are not valid for the address space of the
program making the call.

RETURN VALUES

No values are returned.

ATTRIBUTES

See attributes(7) for descriptions of the following attributes:


+---------------+-----------------+
|ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+---------------+-----------------+
|MT-Level | MT-Safe |
+---------------+-----------------+

SEE ALSO

attributes(7)


February 12, 1997 SYNC_INSTRUCTION_MEMORY(3C)