[PATCH 6.6 341/530] firmware: qcom_scm: use 64-bit calling convention only when client is 64-bit

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6.6-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Kathiravan Thirumoorthy <quic_kathirav@xxxxxxxxxxx>

commit 3337a6fea25370d3d244ec6bb38c71ee86fcf837 upstream.

Per the "SMC calling convention specification", the 64-bit calling
convention can only be used when the client is 64-bit. Whereas the
32-bit calling convention can be used by either a 32-bit or a 64-bit
client.

Currently during SCM probe, irrespective of the client, 64-bit calling
convention is made, which is incorrect and may lead to the undefined
behaviour when the client is 32-bit. Let's fix it.

Cc: stable@xxxxxxxxxxxxxxx
Fixes: 9a434cee773a ("firmware: qcom_scm: Dynamically support SMCCC and legacy conventions")
Reviewed-By: Elliot Berman <quic_eberman@xxxxxxxxxxx>
Signed-off-by: Kathiravan Thirumoorthy <quic_kathirav@xxxxxxxxxxx>
Link: https://lore.kernel.org/r/20230925-scm-v3-1-8790dff6a749@xxxxxxxxxxx
Signed-off-by: Bjorn Andersson <andersson@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/firmware/qcom_scm.c |    7 +++++++
 1 file changed, 7 insertions(+)

--- a/drivers/firmware/qcom_scm.c
+++ b/drivers/firmware/qcom_scm.c
@@ -168,6 +168,12 @@ static enum qcom_scm_convention __get_co
 		return qcom_scm_convention;
 
 	/*
+	 * Per the "SMC calling convention specification", the 64-bit calling
+	 * convention can only be used when the client is 64-bit, otherwise
+	 * system will encounter the undefined behaviour.
+	 */
+#if IS_ENABLED(CONFIG_ARM64)
+	/*
 	 * Device isn't required as there is only one argument - no device
 	 * needed to dma_map_single to secure world
 	 */
@@ -187,6 +193,7 @@ static enum qcom_scm_convention __get_co
 		forced = true;
 		goto found;
 	}
+#endif
 
 	probed_convention = SMC_CONVENTION_ARM_32;
 	ret = __scm_smc_call(NULL, &desc, probed_convention, &res, true);






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