coresight: etm4x: Hide sysfs attributes for unavailable registers

mainline inclusion
from mainline-v5.11-rc5
commit 91b9f018
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I5YCYK
CVE: NA

Reference: https://lore.kernel.org/r/20210110224850.1880240-13-suzuki.poulose@arm.com

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Some of the management registers in ETMv4.x are not accessible
via system register instructions. Thus we must hide the sysfs
files exposing them to the userspace, to prevent system crashes.

This patch adds an is_visible() routine to control the visibility
at runtime for the registers that may not be accessed.

Link: https://lore.kernel.org/r/20210110224850.1880240-13-suzuki.poulose@arm.com


Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Mike Leach <mike.leach@linaro.org>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Link: https://lore.kernel.org/r/20210201181351.1475223-15-mathieu.poirier@linaro.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>