linux-kernel - Re: [PATCH v3 4/7] kprobes: Replace %p with other pointer types

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Message-Id: <20180428134333.6e1b878fc9748dac67387476@kernel.org>
Date:   Sat, 28 Apr 2018 13:43:33 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
        linux-arch@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Ananth N Mavinakayanahalli <ananth@...ibm.com>,
        Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jon Medhurst <tixy@...aro.org>,
        Will Deacon <will.deacon@....com>,
        Arnd Bergmann <arnd@...db.de>,
        David Howells <dhowells@...hat.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        "Tobin C . Harding" <me@...in.cc>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Thomas Richter <tmricht@...ux.ibm.com>,
        akpm@...ux-foundation.org, acme@...nel.org, rostedt@...dmis.org,
        brueckner@...ux.vnet.ibm.com, schwidefsky@...ibm.com,
        stable@...r.kernel.org
Subject: Re: [PATCH v3 4/7] kprobes: Replace %p with other pointer types

On Sat, 28 Apr 2018 00:42:02 +0900
Masami Hiramatsu <mhiramat@...nel.org> wrote:

> > > +/* Caller must NOT call this in usual path. This is only for critical case */
> > >  void dump_kprobe(struct kprobe *kp)
> > >  {
> > > -	printk(KERN_WARNING "Dumping kprobe:\n");
> > > -	printk(KERN_WARNING "Name: %s\nAddress: %p\nOffset: %x\n",
> > > -	       kp->symbol_name, kp->addr, kp->offset);
> > > +	pr_err("Dumping kprobe:\n");
> > > +	pr_err("Name: %s\nOffset: %x\nAddress: %pS\n",
> > > +	       kp->symbol_name, kp->offset, kp->addr);
> > 
> > No, this function should just go away and be replaced by a WARN() in 
> > reenter_kprobe().
> 
> Would you consider to use pr_err() here? If so, I'll move this
> dump as you suggested.

So, this is actually called right before BUG(), which means we found
a non-recoverable error while recovering from reentrant kprobes.
Since the BUG() dumps all registers and stack as same as WARN(),
I think we should keep it.
(I would like to dump all kprobes fields like flags, etc. so that
 we can find it is broken or not.)

Thank you,

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