Messages in this thread | | | Date | Mon, 17 Mar 2008 10:49:56 +0530 | From | Ananth N Mavinakayanahalli <> | Subject | Re: [PATCH] Subject: kprobes-x86: correct post-eip value in post_hander() |
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On Sun, Mar 16, 2008 at 03:21:21AM -0500, Yakov Lerner wrote: > > I was trying to get the address of instruction to be executed > next after the kprobed instruction. But regs->eip in post_handler() > contains value which is useless to the user. It's pre-corrected value. > This value is difficult to use without access to resume_execution(), which > is not exported anyway. > I moved the invocation of post_handler() to *after* resume_execution(). > Now regs->eip contains meaningful value in post_handler(). > > I do not think this change breaks any backward-compatibility. > To make meaning of the old value, post_handler() would need access to > resume_execution() which is not exported. I have difficulty to believe > that previous, uncorrected, regs->eip can be meaningfully used in > post_handler().
resume_execution() exists not just for the program counter fixups after out-of-line singlestepping, but is also as an insurance to put the program counter back to the correct address in case the user's post_handler() mucks around with it. That isn't possible with this change :-(
Ananth
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