firmware: qcom: uefisecapp: Fix memory related IO errors and crashes

It turns out that while the QSEECOM APP_SEND command has specific fields
for request and response buffers, uefisecapp expects them both to be in
a single memory region. Failure to adhere to this has (so far) resulted
in either no response being written to the response buffer (causing an
EIO to be emitted down the line), the SCM call to fail with EINVAL
(i.e., directly from TZ/firmware), or the device to be hard-reset.

While this issue can be triggered deterministically, in the current form
it seems to happen rather sporadically (which is why it has gone
unnoticed during earlier testing). This is likely due to the two
kzalloc() calls (for request and response) being directly after each
other. Which means that those likely return consecutive regions most of
the time, especially when not much else is going on in the system.

Fix this by allocating a single memory region for both request and
response buffers, properly aligning both structs inside it. This
unfortunately also means that the qcom_scm_qseecom_app_send() interface
needs to be restructured, as it should no longer map the DMA regions
separately. Therefore, move the responsibility of DMA allocation (or
mapping) to the caller.

Fixes: 759e7a2b62eb ("firmware: Add support for Qualcomm UEFI Secure Application")
Cc: stable@vger.kernel.org  # 6.7
Tested-by: Johan Hovold <johan+linaro@kernel.org>
Reviewed-by: Johan Hovold <johan+linaro@kernel.org>
Signed-off-by: Maximilian Luz <luzmaximilian@gmail.com>
Tested-by: Konrad Dybcio <konrad.dybcio@linaro.org> # X13s
Link: https://lore.kernel.org/r/20240406130125.1047436-1-luzmaximilian@gmail.com
Signed-off-by: Bjorn Andersson <andersson@kernel.org>

2 files changed, 56 insertions, 9 deletions

diff --git a/include/linux/firmware/qcom/qcom_qseecom.h b/include/linux/firmware/qcom/qcom_qseecom.h
index 5c28298a98bec..366243ee96096 100644
--- a/include/linux/firmware/qcom/qcom_qseecom.h
+++ b/include/linux/firmware/qcom/qcom_qseecom.h
@@ -10,6 +10,7 @@
 #define __QCOM_QSEECOM_H
 
 #include <linux/auxiliary_bus.h>
+#include <linux/dma-mapping.h>
 #include <linux/types.h>
 
 #include <linux/firmware/qcom/qcom_scm.h>
@@ -25,11 +26,56 @@ struct qseecom_client {
 };
 
 /**
+ * qseecom_scm_dev() - Get the SCM device associated with the QSEECOM client.
+ * @client: The QSEECOM client device.
+ *
+ * Returns the SCM device under which the provided QSEECOM client device
+ * operates. This function is intended to be used for DMA allocations.
+ */
+static inline struct device *qseecom_scm_dev(struct qseecom_client *client)
+{
+	return client->aux_dev.dev.parent->parent;
+}
+
+/**
+ * qseecom_dma_alloc() - Allocate DMA memory for a QSEECOM client.
+ * @client:     The QSEECOM client to allocate the memory for.
+ * @size:       The number of bytes to allocate.
+ * @dma_handle: Pointer to where the DMA address should be stored.
+ * @gfp:        Allocation flags.
+ *
+ * Wrapper function for dma_alloc_coherent(), allocating DMA memory usable for
+ * TZ/QSEECOM communication. Refer to dma_alloc_coherent() for details.
+ */
+static inline void *qseecom_dma_alloc(struct qseecom_client *client, size_t size,
+				      dma_addr_t *dma_handle, gfp_t gfp)
+{
+	return dma_alloc_coherent(qseecom_scm_dev(client), size, dma_handle, gfp);
+}
+
+/**
+ * dma_free_coherent() - Free QSEECOM DMA memory.
+ * @client:     The QSEECOM client for which the memory has been allocated.
+ * @size:       The number of bytes allocated.
+ * @cpu_addr:   Virtual memory address to free.
+ * @dma_handle: DMA memory address to free.
+ *
+ * Wrapper function for dma_free_coherent(), freeing memory previously
+ * allocated with qseecom_dma_alloc(). Refer to dma_free_coherent() for
+ * details.
+ */
+static inline void qseecom_dma_free(struct qseecom_client *client, size_t size,
+				    void *cpu_addr, dma_addr_t dma_handle)
+{
+	return dma_free_coherent(qseecom_scm_dev(client), size, cpu_addr, dma_handle);
+}
+
+/**
  * qcom_qseecom_app_send() - Send to and receive data from a given QSEE app.
  * @client:   The QSEECOM client associated with the target app.
- * @req:      Request buffer sent to the app (must be DMA-mappable).
+ * @req:      DMA address of the request buffer sent to the app.
  * @req_size: Size of the request buffer.
- * @rsp:      Response buffer, written to by the app (must be DMA-mappable).
+ * @rsp:      DMA address of the response buffer, written to by the app.
  * @rsp_size: Size of the response buffer.
  *
  * Sends a request to the QSEE app associated with the given client and read
@@ -43,8 +89,9 @@ struct qseecom_client {
  *
  * Return: Zero on success, nonzero on failure.
  */
-static inline int qcom_qseecom_app_send(struct qseecom_client *client, void *req, size_t req_size,
-					void *rsp, size_t rsp_size)
+static inline int qcom_qseecom_app_send(struct qseecom_client *client,
+					dma_addr_t req, size_t req_size,
+					dma_addr_t rsp, size_t rsp_size)
 {
 	return qcom_scm_qseecom_app_send(client->app_id, req, req_size, rsp, rsp_size);
 }
diff --git a/include/linux/firmware/qcom/qcom_scm.h b/include/linux/firmware/qcom/qcom_scm.h
index ccaf288460546..aaa19f93ac430 100644
--- a/include/linux/firmware/qcom/qcom_scm.h
+++ b/include/linux/firmware/qcom/qcom_scm.h
@@ -118,8 +118,8 @@ bool qcom_scm_lmh_dcvsh_available(void);
 #ifdef CONFIG_QCOM_QSEECOM
 
 int qcom_scm_qseecom_app_get_id(const char *app_name, u32 *app_id);
-int qcom_scm_qseecom_app_send(u32 app_id, void *req, size_t req_size, void *rsp,
-			      size_t rsp_size);
+int qcom_scm_qseecom_app_send(u32 app_id, dma_addr_t req, size_t req_size,
+			      dma_addr_t rsp, size_t rsp_size);
 
 #else /* CONFIG_QCOM_QSEECOM */
 
@@ -128,9 +128,9 @@ static inline int qcom_scm_qseecom_app_get_id(const char *app_name, u32 *app_id)
 	return -EINVAL;
 }
 
-static inline int qcom_scm_qseecom_app_send(u32 app_id, void *req,
-					    size_t req_size, void *rsp,
-					    size_t rsp_size)
+static inline int qcom_scm_qseecom_app_send(u32 app_id,
+					    dma_addr_t req, size_t req_size,
+					    dma_addr_t rsp, size_t rsp_size)
 {
 	return -EINVAL;
 }