On 11/25/2013 04:37 PM, Andi Kleen wrote: > From: Andi Kleen <a...@linux.intel.com> > > [Addressed all addressable review feedback in v2] > > Properly patching running code ("cross modification") > is a quite complicated business on x86. > > The CPU has specific rules that need to be followed, including > multiple global barriers. > > Self modifying code is getting more popular, so it's important > to make it easy to follow the rules. > > The kernel does it properly with text_poke_bp(). But the same > method is hard to do for user programs. > > This patch adds a (x86 specific) text_poke() syscall that exposes > the text_poke_bp() machinery to user programs. > > The interface is practically the same as text_poke_bp, just as > a syscall. I added an extra flags parameter, for future > extension. Right now it is enforced to be 0. > > The call also still has a global lock, so it has some scaling > limitations. If it was commonly used this could be fixed > by setting up a list of break point locations. Then > a lock would only be hold to modify the list. > > Right now the implementation is just as simple as possible.
IIRC someone proposed that, rather than specifying a "handler", that any user thread that traps just wait until the poke completes. This would complicate the kernel implementation a bit, but it would make the user code a good deal simpler. Is there any reason that this is a bad idea? --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/