intel_th: sth: Sanitize packet callback's return values

According to the stm class interface, the packet callback should return
an error if it is asked to generate packets that it doesn't support.
When it succeeds, it should return number of bytes consumed from its
payload. Currently, for FLAG packet it mistakenly returns 1.

This patch addresses these issues.

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 8 insertions, 3 deletions

diff --git a/drivers/hwtracing/intel_th/sth.c b/drivers/hwtracing/intel_th/sth.c
index 56101c33e10f..e1aee61dd7b3 100644
--- a/drivers/hwtracing/intel_th/sth.c
+++ b/drivers/hwtracing/intel_th/sth.c
@@ -94,10 +94,13 @@ static ssize_t sth_stm_packet(struct stm_data *stm_data, unsigned int master,
         case STP_PACKET_TRIG:
                 if (flags & STP_PACKET_TIMESTAMPED)
                         reg += 4;
-                iowrite8(*payload, sth->base + reg);
+                writeb_relaxed(*payload, sth->base + reg);
                 break;
 
         case STP_PACKET_MERR:
+                if (size > 4)
+                        size = 4;
+
                 sth_iowrite(&out->MERR, payload, size);
                 break;
 
@@ -107,8 +110,8 @@ static ssize_t sth_stm_packet(struct stm_data *stm_data, unsigned int master,
                 else
                         outp = (u64 __iomem *)&out->FLAG;
 
-                size = 1;
-                sth_iowrite(outp, payload, size);
+                size = 0;
+                writeb_relaxed(0, outp);
                 break;
 
         case STP_PACKET_USER:
@@ -129,6 +132,8 @@ static ssize_t sth_stm_packet(struct stm_data *stm_data, unsigned int master,
 
                 sth_iowrite(outp, payload, size);
                 break;
+        default:
+                return -ENOTSUPP;
         }
 
         return size;