linux-kernel - Re: [PATCH] coresight: Remove %px for printing pcsr value

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Message-ID: <20180502061039.GB332@leoy-ThinkPad-X240s>
Date:   Wed, 2 May 2018 14:10:39 +0800
From:   Leo Yan <leo.yan@...aro.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     Mathieu Poirier <mathieu.poirier@...aro.org>,
        Jonathan Corbet <corbet@....net>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-doc@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] coresight: Remove %px for printing pcsr value

On Tue, May 01, 2018 at 10:29:46PM -0700, Kees Cook wrote:
> On Tue, May 1, 2018 at 10:00 PM, Leo Yan <leo.yan@...aro.org> wrote:
> > The driver prints pcsr twice: the first time it uses specifier %px to
> > print hexadecimal pcsr value and the second time uses specifier %pS for
> > output kernel symbols.
> >
> > As suggested by Kees, using %pS should be sufficient and %px isn't
> > necessary; the reason is if the pcsr is a kernel space address, we can
> > easily get to know the code line from %pS format, on the other hand, if
> > the pcsr value doesn't fall into kernel space range (e.g. if the CPU is
> > stuck in firmware), %pS also gives out pcsr hexadecimal value.
> >
> > So this commit removes useless %px and update section "Output format"
> > in the document for alignment between the code and document.
> >
> > Suggested-by: Kees Cook <keescook@...omium.org>
> > Cc: Mathieu Poirier <mathieu.poirier@...aro.org>
> > Signed-off-by: Leo Yan <leo.yan@...aro.org>
> 
> Thanks!
> 
> Reviewed-by: Kees Cook <keescook@...omium.org>

Thanks for reviewing, Kees.

> -Kees
> 
> > ---
> >  Documentation/trace/coresight-cpu-debug.txt       | 4 ++--
> >  drivers/hwtracing/coresight/coresight-cpu-debug.c | 2 +-
> >  2 files changed, 3 insertions(+), 3 deletions(-)
> >
> > diff --git a/Documentation/trace/coresight-cpu-debug.txt b/Documentation/trace/coresight-cpu-debug.txt
> > index 2b9b51c..89ab09e 100644
> > --- a/Documentation/trace/coresight-cpu-debug.txt
> > +++ b/Documentation/trace/coresight-cpu-debug.txt
> > @@ -177,11 +177,11 @@ Here is an example of the debugging output format:
> >  ARM external debug module:
> >  coresight-cpu-debug 850000.debug: CPU[0]:
> >  coresight-cpu-debug 850000.debug:  EDPRSR:  00000001 (Power:On DLK:Unlock)
> > -coresight-cpu-debug 850000.debug:  EDPCSR:  [<ffff00000808e9bc>] handle_IPI+0x174/0x1d8
> > +coresight-cpu-debug 850000.debug:  EDPCSR:  handle_IPI+0x174/0x1d8
> >  coresight-cpu-debug 850000.debug:  EDCIDSR: 00000000
> >  coresight-cpu-debug 850000.debug:  EDVIDSR: 90000000 (State:Non-secure Mode:EL1/0 Width:64bits VMID:0)
> >  coresight-cpu-debug 852000.debug: CPU[1]:
> >  coresight-cpu-debug 852000.debug:  EDPRSR:  00000001 (Power:On DLK:Unlock)
> > -coresight-cpu-debug 852000.debug:  EDPCSR:  [<ffff0000087fab34>] debug_notifier_call+0x23c/0x358
> > +coresight-cpu-debug 852000.debug:  EDPCSR:  debug_notifier_call+0x23c/0x358
> >  coresight-cpu-debug 852000.debug:  EDCIDSR: 00000000
> >  coresight-cpu-debug 852000.debug:  EDVIDSR: 90000000 (State:Non-secure Mode:EL1/0 Width:64bits VMID:0)
> > diff --git a/drivers/hwtracing/coresight/coresight-cpu-debug.c b/drivers/hwtracing/coresight/coresight-cpu-debug.c
> > index 9cdb3fb..78a054e 100644
> > --- a/drivers/hwtracing/coresight/coresight-cpu-debug.c
> > +++ b/drivers/hwtracing/coresight/coresight-cpu-debug.c
> > @@ -315,7 +315,7 @@ static void debug_dump_regs(struct debug_drvdata *drvdata)
> >         }
> >
> >         pc = debug_adjust_pc(drvdata);
> > -       dev_emerg(dev, " EDPCSR:  [<%px>] %pS\n", (void *)pc, (void *)pc);
> > +       dev_emerg(dev, " EDPCSR:  %pS\n", (void *)pc);
> >
> >         if (drvdata->edcidsr_present)
> >                 dev_emerg(dev, " EDCIDSR: %08x\n", drvdata->edcidsr);
> > --
> > 2.7.4
> >
> 
> 
> 
> -- 
> Kees Cook
> Pixel Security