Re: [PATCH -tip v2 2/2] [BUGFIX] kprobes/x86: Check Interrupt Flagmodifier when registering probe

[Ananth N Mavinakayanahalli]

On Thu, Mar 14, 2013 at 08:52:43PM +0900, Masami Hiramatsu wrote:
> Currently kprobes check whether the copied instruction modifies
> IF (interrupt flag) on each probe hit. This means not only
> introducing overhead but also involving inat_get_opcode_attribute
> into kprobes hot path, and it can cause an infinit recursive
> call (and kernel panic in the end).
> 
> Actually, since the copied instruction itself never be modified
> on the buffer, it is needless to analyze the instruction every
> probe hit.
> 
> To fix this issue, we checks it only once when registering probe
> and store the result on ainsn->if_modifier.
> 
> Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>
> Reported-by: Timo Juhani Lindfors <timo.lindfors@xxxxxx>
> Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
> Cc: Ananth N Mavinakayanahalli <ananth@xxxxxxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
> Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>

Acked-by: Ananth N Mavinakayanahalli <ananth@xxxxxxxxxx>

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