From mboxrd@z Thu Jan 1 00:00:00 1970 From: leo.yan@linaro.org (Leo Yan) Date: Tue, 10 Apr 2018 00:10:56 +0800 Subject: [PATCH 1/2] coresight: Use %px to print pcsr instead of %p In-Reply-To: References: <1520961871-11196-1-git-send-email-mathieu.poirier@linaro.org> <1520961871-11196-2-git-send-email-mathieu.poirier@linaro.org> Message-ID: <20180409161056.GA13134@leoy-ThinkPad-X240s> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi Mathieu, Kees, On Fri, Apr 06, 2018 at 09:47:31AM -0600, Mathieu Poirier wrote: > On 5 April 2018 at 00:26, Kees Cook wrote: > > On Tue, Mar 13, 2018 at 10:24 AM, Mathieu Poirier > > wrote: > >> From: Leo Yan > >> > >> Commit ad67b74d2469 ("printk: hash addresses printed with %p") lets > >> printk specifier %p to hash all addresses before printing, this was > >> resulting in the high 32 bits of pcsr can only output zeros. So > >> module cannot completely print pc value and it's pointless for debugging > >> purpose. > >> > >> This patch fixes this by using %px to print pcsr instead. > > > > Why is %p (and now %px) needed here at all? %pS is already used, which > > should give useful debugging details, yes? > > Hey Leo, > > I've taken a second look at this and Kees has a point, %pS should be > sufficient here. Please test again and see if %px is absolutely > necessary. If you think that is the case please provide a snapshot of > the corner case that makes the change mandatory. Sorry I missed replying for this patch due to my email filter and thanks for suggestion. I can think out one case which should use %px: if CPU is locked up in firmwares (e.g. NS-EL2 or ARM-TF in S-EL3), we can rely on %px to read back PC hex value; for this case the CPU PC address is out of kernel space. How about you guys think for this? Thanks, Leo Yan