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Thu, 06 Nov 2025 09:05:04 -0800 (PST) Received: from linaro.org ([217.38.114.219]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-42ac679d54fsm104227f8f.45.2025.11.06.09.05.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 06 Nov 2025 09:05:03 -0800 (PST) From: Mike Leach To: coresight@lists.linaro.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Cc: suzuki.poulose@arm.com, leo.yan@arm.com, james.clark@linaro.org, Mike Leach Subject: [PATCH] coresight: tmc: Prevent sysfs parameter changes if sink in use Date: Thu, 6 Nov 2025 17:04:59 +0000 Message-Id: <20251106170459.2348-1-mike.leach@linaro.org> X-Mailer: git-send-email 2.32.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" The sysfs files that change the operational parameters for TMC buffer_size, stop_on_flush and trigger_cntr are writable when the TMC is in use. The new values will have no effect and be silently ignored. Alter the sysfs functions to return -EBUSY if the TMC is currently in use, and also protect the write values using the spinlock. Signed-off-by: Mike Leach --- .../hwtracing/coresight/coresight-tmc-core.c | 41 ++++++++++++++++--- 1 file changed, 35 insertions(+), 6 deletions(-) diff --git a/drivers/hwtracing/coresight/coresight-tmc-core.c b/drivers/hwt= racing/coresight/coresight-tmc-core.c index 36599c431be6..a1216a1f9681 100644 --- a/drivers/hwtracing/coresight/coresight-tmc-core.c +++ b/drivers/hwtracing/coresight/coresight-tmc-core.c @@ -489,15 +489,24 @@ static ssize_t trigger_cntr_store(struct device *dev, const char *buf, size_t size) { int ret; - unsigned long val; + unsigned long val, flags; struct tmc_drvdata *drvdata =3D dev_get_drvdata(dev->parent); =20 ret =3D kstrtoul(buf, 16, &val); if (ret) return ret; =20 + /* do not permit write if the sink is currently in use */ + raw_spin_lock_irqsave(&drvdata->spinlock, flags); + if (coresight_get_mode(drvdata->csdev) !=3D CS_MODE_DISABLED) { + ret =3D -EBUSY; + goto out; + } drvdata->trigger_cntr =3D val; - return size; + ret =3D size; +out: + raw_spin_unlock_irqrestore(&drvdata->spinlock, flags); + return ret; } static DEVICE_ATTR_RW(trigger_cntr); =20 @@ -514,7 +523,7 @@ static ssize_t buffer_size_store(struct device *dev, const char *buf, size_t size) { int ret; - unsigned long val; + unsigned long val, flags; struct tmc_drvdata *drvdata =3D dev_get_drvdata(dev->parent); =20 /* Only permitted for TMC-ETRs */ @@ -527,8 +536,18 @@ static ssize_t buffer_size_store(struct device *dev, /* The buffer size should be page aligned */ if (val & (PAGE_SIZE - 1)) return -EINVAL; + + /* do not permit write if the sink is currently in use */ + raw_spin_lock_irqsave(&drvdata->spinlock, flags); + if (coresight_get_mode(drvdata->csdev) !=3D CS_MODE_DISABLED) { + ret =3D -EBUSY; + goto out; + } drvdata->size =3D val; - return size; + ret =3D size; +out: + raw_spin_unlock_irqrestore(&drvdata->spinlock, flags); + return ret; } =20 static DEVICE_ATTR_RW(buffer_size); @@ -547,17 +566,27 @@ static ssize_t stop_on_flush_store(struct device *dev, { int ret; u8 val; + unsigned long flags; struct tmc_drvdata *drvdata =3D dev_get_drvdata(dev->parent); =20 ret =3D kstrtou8(buf, 0, &val); if (ret) return ret; + + /* do not permit write if the sink is currently in use */ + raw_spin_lock_irqsave(&drvdata->spinlock, flags); + if (coresight_get_mode(drvdata->csdev) !=3D CS_MODE_DISABLED) { + ret =3D -EBUSY; + goto out; + } if (val) drvdata->stop_on_flush =3D true; else drvdata->stop_on_flush =3D false; - - return size; + ret =3D size; +out: + raw_spin_unlock_irqrestore(&drvdata->spinlock, flags); + return ret; } =20 static DEVICE_ATTR_RW(stop_on_flush); --=20 2.32.0