coresight: etm3x: Adding missing features of Coresight PTM components

In the current driver for Coresight components, two features of PTM
components are missing:

1. Branch Broadcasting (present also in ETM but called Branch Output)
2. Return Stack (only present in PTM v1.0 and PTMv1.1)

These features can be added simply to the code using `mode` field of
`etm_config` struct.

1. **Branch Broadcast** : The branch broadcast feature is present in ETM
components as well and is called Branch output. It allows to retrieve
addresses for direct branch addresses alongside the indirect branch
addresses. For example, it could be useful in cases when tracing without
source code.
2. **Return Stack** : The return stack option allows to retrieve the
return addresses of function calls. It can be useful to avoid CRA
(Code Reuse Attacks) by keeping a shadowstack.

Signed-off-by: Muhammad Abdul Wahab <muhammadabdul.wahab@centralesupelec.fr>
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

2 files changed, 15 insertions, 0 deletions

diff --git a/drivers/hwtracing/coresight/coresight-etm.h b/drivers/hwtracing/coresight/coresight-etm.h
index 4a18ee499965..ad063d7444e1 100644
--- a/drivers/hwtracing/coresight/coresight-etm.h
+++ b/drivers/hwtracing/coresight/coresight-etm.h
@@ -89,11 +89,13 @@
 /* ETMCR - 0x00 */
 #define ETMCR_PWD_DWN           BIT(0)
 #define ETMCR_STALL_MODE        BIT(7)
+#define ETMCR_BRANCH_BROADCAST  BIT(8)
 #define ETMCR_ETM_PRG           BIT(10)
 #define ETMCR_ETM_EN            BIT(11)
 #define ETMCR_CYC_ACC           BIT(12)
 #define ETMCR_CTXID_SIZE        (BIT(14)|BIT(15))
 #define ETMCR_TIMESTAMP_EN      BIT(28)
+#define ETMCR_RETURN_STACK      BIT(29)
 /* ETMCCR - 0x04 */
 #define ETMCCR_FIFOFULL         BIT(23)
 /* ETMPDCR - 0x310 */
@@ -110,8 +112,11 @@
 #define ETM_MODE_STALL          BIT(2)
 #define ETM_MODE_TIMESTAMP      BIT(3)
 #define ETM_MODE_CTXID          BIT(4)
+#define ETM_MODE_BBROAD         BIT(5)
+#define ETM_MODE_RET_STACK      BIT(6)
 #define ETM_MODE_ALL            (ETM_MODE_EXCLUDE | ETM_MODE_CYCACC | \
                                  ETM_MODE_STALL | ETM_MODE_TIMESTAMP | \
+                                 ETM_MODE_BBROAD | ETM_MODE_RET_STACK | \
                                  ETM_MODE_CTXID | ETM_MODE_EXCL_KERN | \
                                  ETM_MODE_EXCL_USER)
 
diff --git a/drivers/hwtracing/coresight/coresight-etm3x-sysfs.c b/drivers/hwtracing/coresight/coresight-etm3x-sysfs.c
index 5ea090955c08..ca98ad13bb8c 100644
--- a/drivers/hwtracing/coresight/coresight-etm3x-sysfs.c
+++ b/drivers/hwtracing/coresight/coresight-etm3x-sysfs.c
@@ -164,6 +164,16 @@ static ssize_t mode_store(struct device *dev,
         else
                 config->ctrl &= ~ETMCR_CTXID_SIZE;
 
+        if (config->mode & ETM_MODE_BBROAD)
+                config->ctrl |= ETMCR_BRANCH_BROADCAST;
+        else
+                config->ctrl &= ~ETMCR_BRANCH_BROADCAST;
+
+        if (config->mode & ETM_MODE_RET_STACK)
+                config->ctrl |= ETMCR_RETURN_STACK;
+        else
+                config->ctrl &= ~ETMCR_RETURN_STACK;
+
         if (config->mode & (ETM_MODE_EXCL_KERN | ETM_MODE_EXCL_USER))
                 etm_config_trace_mode(config);