linux-kernel - Re: [PATCH 1/4] kprobes: adjust kprobe addr for KPROBES_ON

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Date:   Tue, 20 Aug 2019 01:51:52 +0000
From:   Jisheng Zhang <Jisheng.Zhang@...aptics.com>
To:     "Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>
CC:     Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
        Borislav Petkov <bp@...en8.de>,
        Catalin Marinas <catalin.marinas@....com>,
        "David S. Miller" <davem@...emloft.net>,
        "H. Peter Anvin" <hpa@...or.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Will Deacon <will@...nel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>
Subject: Re: [PATCH 1/4] kprobes: adjust kprobe addr for KPROBES_ON_FTRACE

On Mon, 19 Aug 2019 22:13:02 +0530 "Naveen N. Rao"  wrote:

> CAUTION: Email originated externally, do not click links or open attachments unless you recognize the sender and know the content is safe.
> 
> 
> Jisheng Zhang wrote:
> > For KPROBES_ON_FTRACE case, we need to adjust the kprobe's addr
> > correspondingly.
> >
> > Signed-off-by: Jisheng Zhang <Jisheng.Zhang@...aptics.com>
> > ---
> >  kernel/kprobes.c | 3 +++
> >  1 file changed, 3 insertions(+)
> >
> > diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> > index 9873fc627d61..f8400753a8a9 100644
> > --- a/kernel/kprobes.c
> > +++ b/kernel/kprobes.c
> > @@ -1560,6 +1560,9 @@ int register_kprobe(struct kprobe *p)
> >       addr = kprobe_addr(p);
> >       if (IS_ERR(addr))
> >               return PTR_ERR(addr);
> > +#ifdef CONFIG_KPROBES_ON_FTRACE
> > +     addr = (kprobe_opcode_t *)ftrace_call_adjust((unsigned long)addr);
> > +#endif
> >       p->addr = addr;  
> 
> I'm not sure what this is achieving, but looks wrong to me.

Indeed, I didn't take care of non-ftrace addr when KPROBES_ON_FTRACE, will
update in next version.

thanks

> 
> If you intend to have kprobes default to using ftrace entry for probing
> functions, consider over-riding kprobe_lookup_name() -- see powerpc
> variant for example.
> 
> 
> - Naveen
>