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    Subject[PATCH 5.14 189/849] coresight: trbe: Defer the probe on offline CPUs
    Date
    From: Suzuki K Poulose <suzuki.poulose@arm.com>

    commit a08025b3fe56185290a1ea476581f03ca733f967 upstream.

    If a CPU is offline during the driver init, we could end up causing
    a kernel crash trying to register the coresight device for the TRBE
    instance. The trbe_cpudata for the TRBE instance is initialized only
    when it is probed. Otherwise, we could end up dereferencing a NULL
    cpudata->drvdata.

    e.g:

    [ 0.149999] coresight ete0: CPU0: ete v1.1 initialized
    [ 0.149999] coresight-etm4x ete_1: ETM arch init failed
    [ 0.149999] coresight-etm4x: probe of ete_1 failed with error -22
    [ 0.150085] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000050
    [ 0.150085] Mem abort info:
    [ 0.150085] ESR = 0x96000005
    [ 0.150085] EC = 0x25: DABT (current EL), IL = 32 bits
    [ 0.150085] SET = 0, FnV = 0
    [ 0.150085] EA = 0, S1PTW = 0
    [ 0.150085] Data abort info:
    [ 0.150085] ISV = 0, ISS = 0x00000005
    [ 0.150085] CM = 0, WnR = 0
    [ 0.150085] [0000000000000050] user address but active_mm is swapper
    [ 0.150085] Internal error: Oops: 96000005 [#1] PREEMPT SMP
    [ 0.150085] Modules linked in:
    [ 0.150085] Hardware name: FVP Base RevC (DT)
    [ 0.150085] pstate: 00800009 (nzcv daif -PAN +UAO -TCO BTYPE=--)
    [ 0.150155] pc : arm_trbe_register_coresight_cpu+0x74/0x144
    [ 0.150155] lr : arm_trbe_register_coresight_cpu+0x48/0x144
    ...

    [ 0.150237] Call trace:
    [ 0.150237] arm_trbe_register_coresight_cpu+0x74/0x144
    [ 0.150237] arm_trbe_device_probe+0x1c0/0x2d8
    [ 0.150259] platform_drv_probe+0x94/0xbc
    [ 0.150259] really_probe+0x1bc/0x4a8
    [ 0.150266] driver_probe_device+0x7c/0xb8
    [ 0.150266] device_driver_attach+0x6c/0xac
    [ 0.150266] __driver_attach+0xc4/0x148
    [ 0.150266] bus_for_each_dev+0x7c/0xc8
    [ 0.150266] driver_attach+0x24/0x30
    [ 0.150266] bus_add_driver+0x100/0x1e0
    [ 0.150266] driver_register+0x78/0x110
    [ 0.150266] __platform_driver_register+0x44/0x50
    [ 0.150266] arm_trbe_init+0x28/0x84
    [ 0.150266] do_one_initcall+0x94/0x2bc
    [ 0.150266] do_initcall_level+0xa4/0x158
    [ 0.150266] do_initcalls+0x54/0x94
    [ 0.150319] do_basic_setup+0x24/0x30
    [ 0.150319] kernel_init_freeable+0xe8/0x14c
    [ 0.150319] kernel_init+0x14/0x18c
    [ 0.150319] ret_from_fork+0x10/0x30
    [ 0.150319] Code: f94012c8 b0004ce2 9134a442 52819801 (f9402917)
    [ 0.150319] ---[ end trace d23e0cfe5098535e ]---
    [ 0.150346] Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b

    Fix this by skipping the step, if we are unable to probe the CPU.

    Fixes: 3fbf7f011f24 ("coresight: sink: Add TRBE driver")
    Reported-by: Bransilav Rankov <branislav.rankov@arm.com>
    Cc: Anshuman Khandual <anshuman.khandual@arm.com>
    Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
    Cc: Mike Leach <mike.leach@linaro.org>
    Cc: Leo Yan <leo.yan@linaro.org>
    Cc: stable <stable@vger.kernel.org>
    Tested-by: Branislav Rankov <branislav.rankov@arm.com>
    Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
    Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
    Link: https://lore.kernel.org/r/20211014142238.2221248-1-suzuki.poulose@arm.com
    Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/hwtracing/coresight/coresight-trbe.c | 8 +++++++-
    1 file changed, 7 insertions(+), 1 deletion(-)

    --- a/drivers/hwtracing/coresight/coresight-trbe.c
    +++ b/drivers/hwtracing/coresight/coresight-trbe.c
    @@ -869,6 +869,10 @@ static void arm_trbe_register_coresight_
    if (WARN_ON(trbe_csdev))
    return;

    + /* If the TRBE was not probed on the CPU, we shouldn't be here */
    + if (WARN_ON(!cpudata->drvdata))
    + return;
    +
    dev = &cpudata->drvdata->pdev->dev;
    desc.name = devm_kasprintf(dev, GFP_KERNEL, "trbe%d", cpu);
    if (!desc.name)
    @@ -950,7 +954,9 @@ static int arm_trbe_probe_coresight(stru
    return -ENOMEM;

    for_each_cpu(cpu, &drvdata->supported_cpus) {
    - smp_call_function_single(cpu, arm_trbe_probe_cpu, drvdata, 1);
    + /* If we fail to probe the CPU, let us defer it to hotplug callbacks */
    + if (smp_call_function_single(cpu, arm_trbe_probe_cpu, drvdata, 1))
    + continue;
    if (cpumask_test_cpu(cpu, &drvdata->supported_cpus))
    arm_trbe_register_coresight_cpu(drvdata, cpu);
    if (cpumask_test_cpu(cpu, &drvdata->supported_cpus))

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