linux-kernel - Re: [PATCH v9 5/7] coresight: tmc: Add support for reading crash data

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Date: Thu, 20 Jun 2024 09:44:25 +0530
From: Linu Cherian <lcherian@...vell.com>
To: James Clark <james.clark@....com>
CC: <linux-arm-kernel@...ts.infradead.org>, <coresight@...ts.linaro.org>,
        <linux-kernel@...r.kernel.org>, <robh+dt@...nel.org>,
        <krzysztof.kozlowski+dt@...aro.org>, <conor+dt@...nel.org>,
        <devicetree@...r.kernel.org>, <sgoutham@...vell.com>,
        <gcherian@...vell.com>, Anil Kumar Reddy <areddy3@...vell.com>,
        Tanmay Jagdale <tanmay@...vell.com>, <suzuki.poulose@....com>,
        <mike.leach@...aro.org>
Subject: Re: [PATCH v9 5/7] coresight: tmc: Add support for reading crash data

Hi James,

On 2024-06-05 at 16:00:39, James Clark (james.clark@....com) wrote:
> 
> 
> On 05/06/2024 09:17, Linu Cherian wrote:
> > * Introduce a new mode CS_MODE_READ_CRASHDATA for reading trace
> >   captured in previous crash/watchdog reset.
> > 
> > * Add special device files for reading ETR/ETF crash data.
> > 
> > * User can read the crash data as below
> > 
> >   For example, for reading crash data from tmc_etf sink
> > 
> >   #dd if=/dev/crash_tmc_etfXX of=~/cstrace.bin
> > 
> 
> Hi Linu,
> 
> I think you are missing the removal of the new crash file when the
> device is unloaded.
> 
> If you reload the module you get some errors:
> 
>   # rmmod coresight_tmc
>   # modprobe coresight_tmc dyndbg=+p
> 
>   kobject: kobject_add_internal failed for crash_tmc_etf0 with -EEXIST,
>     don't try to register things with the same name in the same
>     directory.
>   coresight tmc_etf0: Failed to setup user interface for crashdata
>   sysfs: cannot create duplicate filename '/devices/virtual
>    /misc/crash_tmc_etr0'
> 
> I'm not sure if it's related, but there are also some kasan errors at
> the same time which I haven't seen before:
>

Okay, somehow i missed testing with modules. Will fix those.

>   BUG: KASAN: slab-use-after-free in strcmp+0x94/0xd0
>   Read of size 1 at addr ffff00080b271be0 by task modprobe/570
>   CPU: 2 PID: 570 Comm: modprobe Not tainted 6.9.0-rc4+ #71
>   Hardware name: ARM LTD ARM Juno Development Platform/ARM Juno

Okay. Will check if its reproducible and related.

Thanks.

>     Development Platform, BIOS EDK II Oct 19 2019
>   Call trace:
>    dump_backtrace+0x100/0x158
>    show_stack+0x24/0x38
>    dump_stack_lvl+0x3c/0x98
>    print_report+0x178/0x508
>    kasan_report+0xc0/0x120
>    __asan_report_load1_noabort+0x20/0x30
>    strcmp+0x94/0xd0
>    cti_add_assoc_to_csdev+0x174/0x430 [coresight_cti]
>    coresight_register+0x414/0x500 [coresight]
>    __tmc_probe+0xd40/0x1340 [coresight_tmc]
>    tmc_probe+0x60/0x98 [coresight_tmc]
>    amba_probe+0x604/0x838
>    really_probe+0x318/0x780
>    __driver_probe_device+0x168/0x318
>    driver_probe_device+0x78/0x2a0
>    __driver_attach+0x22c/0x538
>    bus_for_each_dev+0x1bc/0x1f0
>    driver_attach+0x54/0x70
>    bus_add_driver+0x2a8/0x4c0
>    driver_register+0x168/0x2b8
>    amba_driver_register+0x74/0x98
>    coresight_init_driver+0x34/0xa8 [coresight]
>    init_module+0x34/0xfb8 [coresight_tmc]
>    do_one_initcall+0x1a0/0x8d0
>    do_init_module+0x1f8/0x588
>    load_module+0x3c20/0x44c0
>    __arm64_sys_finit_module+0x3c8/0x638
>    invoke_syscall+0x78/0x218
>    el0_svc_common+0x160/0x1d8
>    do_el0_svc+0x50/0x68
>    el0_svc+0x4c/0xc0
>    el0t_64_sync_handler+0x84/0x100
>    el0t_64_sync+0x190/0x198
> 
> _______________________________________________
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> linux-arm-kernel@...ts.infradead.org
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