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@vger.kernel.org Fixes: 9a434cee773a ("firmware: qcom_scm: Dynamically support SMCCC and legacy conventions") Reviewed-By: Elliot Berman quic_eberman@quicinc.com Signed-off-by: Kathiravan Thirumoorthy quic_kathirav@quicinc.com --- Changes in V3: - reworded the commit title and msg - pick up the R-b tag

Changes in V2: - Added the Fixes tag and cc'd stable mailing list --- drivers/firmware/qcom_scm.c | 7 +++++++ 1 file changed, 7 insertions(+)

diff --git a/drivers/firmware/qcom_scm.c b/drivers/firmware/qcom_scm.c index c2c7fafef34b..520de9b5633a 100644 --- a/drivers/firmware/qcom_scm.c +++ b/drivers/firmware/qcom_scm.c @@ -215,6 +215,12 @@ static enum qcom_scm_convention __get_convention(void) if (likely(qcom_scm_convention != SMC_CONVENTION_UNKNOWN)) 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 @@ -235,6 +241,7 @@ static enum qcom_scm_convention __get_convention(void) forced = true; goto found; } +#endif

probed_convention = SMC_CONVENTION_ARM_32; ret = __scm_smc_call(NULL, &desc, probed_convention, &res, true);

--- base-commit: 8fff9184d1b5810dca5dd1a02726d4f844af88fc change-id: 20230925-scm-d62c6cd1947b

Best regards,