linux-kernel - Re: [PATCH v2 1/3] kprobes/x86: use instruction_pointer and instruction_pointer

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Message-Id: <20190823235127.6b1ab6bdb3a280b64ca8585e@kernel.org>
Date:   Fri, 23 Aug 2019 23:51:27 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Jisheng Zhang <Jisheng.Zhang@...aptics.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Catalin Marinas <catalin.marinas@....com>,
        Jonathan Corbet <corbet@....net>,
        Will Deacon <will@...nel.org>, Ingo Molnar <mingo@...hat.com>,
        Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>,
        Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
        "David S. Miller" <davem@...emloft.net>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v2 1/3] kprobes/x86: use instruction_pointer and
 instruction_pointer_set

Hi Jisheng,

On Wed, 21 Aug 2019 02:09:10 +0000
Jisheng Zhang <Jisheng.Zhang@...aptics.com> wrote:

> > > In v2, actually, the arm64 version's kprobe_ftrace_handler() is the same
> > > as x86's, the only difference is comment, e.g
> > >
> > > /* Kprobe handler expects regs->ip = ip + 1 as breakpoint hit */
> > >
> > > while in arm64
> > >
> > > /* Kprobe handler expects regs->pc = ip + 1 as breakpoint hit */  
> > 
> > As Peter pointed, on arm64, is that really 1 or 4 bytes?
> > This part is heavily depends on the processor software-breakpoint
> > implementation.
> 
> Per my understanding, the "+1" here means "+ one kprobe_opcode_t".

No, that is the size of INT3. It just emulates the software trap on x86.

Thank you,
-- 
Masami Hiramatsu <mhiramat@...nel.org>