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Date: Thu, 26 Jul 2007 16:06:52 +0900 From: Paul Mundt <lethal@...ux-sh.org> To: jidong xiao <jidong.xiao@...il.com> Cc: linux-kernel@...r.kernel.org Subject: Re: What's does KPROBE_ENTRY mean? On Thu, Jul 26, 2007 at 02:50:38PM +0800, jidong xiao wrote: > Thanks.So if I don't care any probes, and I actually don't need to > take use of kprobes, then I can use the functions defined through > KPROBE_ENTRY() the same way as those defined via ENTRY(), right? > Yes, there's nothing special about KPROBE_ENTRY() other than the section placement. It even wraps in to ENTRY() after the .pushsection. As you can see from kernel/kprobes.c: static int __kprobes in_kprobes_functions(unsigned long addr) { if (addr >= (unsigned long)__kprobes_text_start && addr < (unsigned long)__kprobes_text_end) return -EINVAL; return 0; } ... and in __register_kprobe(): if (!kernel_text_address((unsigned long) p->addr) || in_kprobes_functions((unsigned long) p->addr)) return -EINVAL; So the only behavioural change for these symbols is that insertion of probes is prohibited. There is nothing inherently special about them otherwise, and platforms that don't enable kprobes aren't going to care either. One curious thing is that while KPROBE_ENTRY() unconditionally does a .pushsection .kprobes.text, __kprobes does this conditionally depending on CONFIG_KPROBES. While this doesn't hurt anything, it's inconsistent to say the least. We should probably either make __kprobes explicitly always use .kprobes.text, or just wrap KPROBE_ENTRY to ENTRY directly and forego the .pushsection when CONFIG_KPROBES=n. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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