问题
I am writing a JIT on ARM Linux that executes an instruction set that contains self-modifying code. The instruction set does not have any cache flush instructions (similar to x86 in that respect).
If I write out some code to a page and then call mprotect on that page, is that sufficient to invalidate the instruction cache? Or do I also need to use the cacheflush syscall on those pages?
回答1:
You'd expect that the mmap/mprotect syscalls would establish mappings that are updated immediately, and need no further interaction to use the memory ranges as specified. I see that the kernel does indeed flush caches on mprotect. In that case, no cache flush would be required.
However, I also see that some versions of libc do call cacheflush after mprotect, which would imply that some environments would need the caches flushed (or have previously). I'd take a guess that this is a workaround to a bug.
You could always add the call to cacheflush; although it's extra code, it shouldn't be to harmful - at worst, the caches will already be flushed. You could always write a quick test and see what happens...
回答2:
I believe you do not have to explicitly flush the cache.
Which processor is this? ARMv5? ARMv7?
来源：https://stackoverflow.com/questions/2777725/does-mprotect-flush-the-instruction-cache-on-arm-linux