[PATCH v1] misc: fastrpc: Trigger a panic using BUG_ON in device release

[Abhishek Singh]

The user process on ARM closes the device node while closing the
session, triggers a remote call to terminate the PD running on the
DSP. If the DSP is in an unstable state and cannot process the remote
request from the HLOS, glink fails to deliver the kill request to the
DSP, resulting in a timeout error. Currently, this error is ignored,
and the session is closed, causing all the SMMU mappings associated
with that specific PD to be removed. However, since the PD is still
operational on the DSP, any attempt to access these SMMU mappings
results in an SMMU fault, leading to a panic.  As the SMMU mappings
have already been removed, there is no available information on the
DSP to determine the root cause of its unresponsiveness to remote
calls. As the DSP is unresponsive to all process remote calls, use
BUG_ON to prevent the removal of SMMU mappings and to properly
identify the root cause of the DSP’s unresponsiveness to the remote
calls.

Signed-off-by: Abhishek Singh <quic_abhishes at quicinc.com>
---
 drivers/misc/fastrpc.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
index 5204fda51da3..bac9c749564c 100644
--- a/drivers/misc/fastrpc.c
+++ b/drivers/misc/fastrpc.c
@@ -97,6 +97,7 @@
 #define FASTRPC_RMID_INIT_CREATE_STATIC	8
 #define FASTRPC_RMID_INIT_MEM_MAP      10
 #define FASTRPC_RMID_INIT_MEM_UNMAP    11
+#define PROCESS_KILL_SC 0x01010000
 
 /* Protection Domain(PD) ids */
 #define ROOT_PD		(0)
@@ -1128,6 +1129,9 @@ static int fastrpc_invoke_send(struct fastrpc_session_ctx *sctx,
 	fastrpc_context_get(ctx);
 
 	ret = rpmsg_send(cctx->rpdev->ept, (void *)msg, sizeof(*msg));
+	/* trigger panic if glink communication is broken and the message is for PD kill */
+	BUG_ON((ret == -ETIMEDOUT) && (handle == FASTRPC_INIT_HANDLE) &&
+			(ctx->sc == PROCESS_KILL_SC));
 
 	if (ret)
 		fastrpc_context_put(ctx);
-- 
2.25.1