linux-kernel - Re: [PATCH] coresight: cti: Fix null pointer error on CTI init before ETM

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Message-ID: <f1bf0342-20e3-0a98-d6e4-1ee6e128b902@arm.com>
Date:   Thu, 24 Nov 2022 13:32:36 +0000
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     Mike Leach <mike.leach@...aro.org>,
        linux-arm-kernel@...ts.infradead.org, coresight@...ts.linaro.org,
        linux-kernel@...r.kernel.org
Cc:     mathieu.poirier@...aro.org, leo.yan@...aro.org, acme@...nel.org
Subject: Re: [PATCH] coresight: cti: Fix null pointer error on CTI init before
 ETM

On 23/11/2022 19:38, Mike Leach wrote:
> When CTI is discovered first then the function
> coresight_set_assoc_ectdev_mutex() is called to set the association
> between CTI and ETM device. Recent lockdep fix passes a null pointer. >
> This patch passes the correct pointer.
> 
> Before patch: log of boot oops sequence with CTI discovered first:
> 
> [   12.424091]  cs_system_cfg: CoreSight Configuration manager initialised
> [   12.483474] coresight cti_sys0: CTI initialized
> [   12.488109] coresight cti_sys1: CTI initialized
> [   12.503594] coresight cti_cpu0: CTI initialized
> [   12.517877] coresight-cpu-debug 850000.debug: Coresight debug-CPU0 initialized
> [   12.523479] coresight-cpu-debug 852000.debug: Coresight debug-CPU1 initialized
> [   12.529926] coresight-cpu-debug 854000.debug: Coresight debug-CPU2 initialized
> [   12.541808] coresight stm0: STM32 initialized
> [   12.544421] coresight-cpu-debug 856000.debug: Coresight debug-CPU3 initialized
> [   12.585639] coresight cti_cpu1: CTI initialized
> [   12.614028] coresight cti_cpu2: CTI initialized
> [   12.631679] CSCFG registered etm0
> [   12.633920] coresight etm0: CPU0: etm v4.0 initialized
> [   12.656392] coresight cti_cpu3: CTI initialized
> 
> ...
> 
> [   12.708383] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000348
> 
> ...
> 
> [   12.755094] Internal error: Oops: 0000000096000044 [#1] SMP
> [   12.761817] Modules linked in: coresight_etm4x(+) coresight_tmc coresight_cpu_debug coresight_replicator coresight_funnel coresight_cti coresight_tpiu coresight_stm coresight
> [   12.767210] CPU: 3 PID: 1346 Comm: systemd-udevd Not tainted 6.1.0-rc3tid-v6tid-v6-235166-gf7f7d7a2204a-dirty #498
> [   12.782827] Hardware name: Qualcomm Technologies, Inc. APQ 8016 SBC (DT)
> [   12.793154] pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> [   12.800010] pc : coresight_set_assoc_ectdev_mutex+0x30/0x50 [coresight]
> [   12.806694] lr : coresight_set_assoc_ectdev_mutex+0x30/0x50 [coresight]
> 
> ...
> 
> [   12.885064] Call trace:
> [   12.892352]  coresight_set_assoc_ectdev_mutex+0x30/0x50 [coresight]
> [   12.894693]  cti_add_assoc_to_csdev+0x144/0x1b0 [coresight_cti]
> [   12.900943]  coresight_register+0x2c8/0x320 [coresight]
> [   12.906844]  etm4_add_coresight_dev.isra.27+0x148/0x280 [coresight_etm4x]
> [   12.912056]  etm4_probe+0x144/0x1c0 [coresight_etm4x]
> [   12.918998]  etm4_probe_amba+0x40/0x78 [coresight_etm4x]
> [   12.924032]  amba_probe+0x11c/0x1f0
> 
> After patch: similar log
> 
> [   12.444467]  cs_system_cfg: CoreSight Configuration manager initialised
> [   12.456329] coresight-cpu-debug 850000.debug: Coresight debug-CPU0 initialized
> [   12.456754] coresight-cpu-debug 852000.debug: Coresight debug-CPU1 initialized
> [   12.469672] coresight-cpu-debug 854000.debug: Coresight debug-CPU2 initialized
> [   12.476098] coresight-cpu-debug 856000.debug: Coresight debug-CPU3 initialized
> [   12.532409] coresight stm0: STM32 initialized
> [   12.533708] coresight cti_sys0: CTI initialized
> [   12.539478] coresight cti_sys1: CTI initialized
> [   12.550106] coresight cti_cpu0: CTI initialized
> [   12.633931] coresight cti_cpu1: CTI initialized
> [   12.634664] coresight cti_cpu2: CTI initialized
> [   12.638090] coresight cti_cpu3: CTI initialized
> [   12.721136] CSCFG registered etm0
> 
> ...
> 
> [   12.762643] CSCFG registered etm1
> [   12.762666] coresight etm1: CPU1: etm v4.0 initialized
> [   12.776258] CSCFG registered etm2
> [   12.776282] coresight etm2: CPU2: etm v4.0 initialized
> [   12.784357] CSCFG registered etm3
> [   12.785455] coresight etm3: CPU3: etm v4.0 initialized
> 
> Error can also be triggered by manually starting the modules using modprobe
> in the following order:
> 
> root@...aro-developer:/home/linaro/cs-mods# modprobe coresight
> root@...aro-developer:/home/linaro/cs-mods# modprobe coresight-cti
> root@...aro-developer:/home/linaro/cs-mods# modprobe coresight-etm4x
> 
> Tested on Dragonboard DB410c
> Applies to coresight/next
> 

It is not just the NULL pointer reference, but also the code is using
wrong "device" as csdev. The patch looks good to me. I will queue this

Suzuki