linux-kernel - Re: [PATCH -tip 0/3] x86/kprobes: Remoev single-step trap from x86 kprobes

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Date:   Wed, 17 Mar 2021 23:55:22 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     Andy Lutomirski <luto@...nel.org>, Ingo Molnar <mingo@...nel.org>,
        Oleg Nesterov <oleg@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
        "David S . Miller" <davem@...emloft.net>, X86 ML <x86@...nel.org>,
        Andrew Cooper <andrew.cooper3@...rix.com>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH -tip 0/3] x86/kprobes: Remoev single-step trap from x86
 kprobes

Hi Andy,

Would you think you still need this series to remove iret to kernel?

Thank you,

On Wed,  3 Mar 2021 00:25:12 +0900
Masami Hiramatsu <mhiramat@...nel.org> wrote:

> Hi,
> 
> Here is a series of patches to remove the single-step debug trap from the
> x86 kprobe.
> 
> The first 2 patches ([1/3][2/3]) are bugfixes which I've sent recently;
> 
>  https://lore.kernel.org/lkml/161425451732.93763.18329509061375062554.stgit@devnote2/
> 
> And [3/3] is actually the patch to remove single-step from kprobes. The RFC
> version is here;
> 
>  https://lore.kernel.org/lkml/161460768474.430263.18425867006584111900.stgit@devnote2/
> 
> This uses int3 as Andy suggested instead of the debug trap, for removing the
> IRET which returns to kernel.
> Some instructions must be emulated and some instructions becomes not able
> to be probed, but as far as I can see those are not rare case.
> 
> Thank you,
> 
> ---
> 
> Masami Hiramatsu (3):
>       x86/kprobes: Retrieve correct opcode for group instruction
>       x86/kprobes: Identify far indirect JMP correctly
>       x86/kprobes: Use int3 instead of debug trap for single-step
> 
> 
>  arch/x86/include/asm/kprobes.h |   21 +-
>  arch/x86/kernel/kprobes/core.c |  524 ++++++++++++++++++++++++++--------------
>  arch/x86/kernel/traps.c        |    3 
>  3 files changed, 358 insertions(+), 190 deletions(-)
> 
> --
> Masami Hiramatsu (Linaro) <mhiramat@...nel.org>


-- 
Masami Hiramatsu <mhiramat@...nel.org>