Messages in this thread | | | Subject | Re: [PATCH 08/15] x86/alternatives: Teach text_poke_bp() to emulate instructions | From | Andy Lutomirski <> | Date | Fri, 7 Jun 2019 11:10:19 -0700 |
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> On Jun 7, 2019, at 10:34 AM, Peter Zijlstra <peterz@infradead.org> wrote: > > On Sat, Jun 08, 2019 at 12:47:08AM +0900, Masami Hiramatsu wrote: > >>> This fits almost all text_poke_bp() users, except >>> arch_unoptimize_kprobe() which restores random text, and for that site >>> we have to build an explicit emulate instruction. >> >> Hm, actually it doesn't restores randome text, since the first byte >> must always be int3. As the function name means, it just unoptimizes >> (jump based optprobe -> int3 based kprobe). >> Anyway, that is not an issue. With this patch, optprobe must still work. > > I thought it basically restored 5 bytes of original text (with no > guarantee it is a single instruction, or even a complete instruction), > with the first byte replaced with INT3. >
I am surely missing some kprobe context, but is it really safe to use this mechanism to replace more than one instruction?
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