2023-09-25 15:14:53

by Kathiravan Thirumoorthy

Subject: [PATCH v3] firmware: qcom_scm: use 64-bit calling convention only when client is 64-bit

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: [email protected]
Fixes: 9a434cee773a ("firmware: qcom_scm: Dynamically support SMCCC and legacy conventions")
Reviewed-By: Elliot Berman <[email protected]>
Signed-off-by: Kathiravan Thirumoorthy <[email protected]>
---
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,
--
Kathiravan Thirumoorthy <[email protected]>

2023-09-28 00:31:57

by Bjorn Andersson

Subject: Re: [PATCH v3] firmware: qcom_scm: use 64-bit calling convention only when client is 64-bit

On Mon, 25 Sep 2023 13:59:22 +0530, Kathiravan Thirumoorthy wrote:
> 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.
>
> [...]

Applied, thanks!

[1/1] firmware: qcom_scm: use 64-bit calling convention only when client is 64-bit
commit: 3337a6fea25370d3d244ec6bb38c71ee86fcf837

Best regards,
--
Bjorn Andersson <[email protected]>