[PATCH V3 05/10] remoteproc: qcom_q6v5_mss: Use a carveout to authenticate modem headers

[Sibi Sankar <quic_sibis@xxxxxxxxxxx>]

Any access to the dynamically allocated metadata region by the application
processor after assigning it to the remote Q6 will result in a XPU
violation. Fix this by replacing the dynamically allocated memory region
with a no-map carveout and unmap the modem metadata memory region before
passing control to the remote Q6.

Reported-and-tested-by: Amit Pundir <amit.pundir@xxxxxxxxxx>
Fixes: 6c5a9dc2481b ("remoteproc: qcom: Make secure world call for mem ownership switch")
Signed-off-by: Sibi Sankar <quic_sibis@xxxxxxxxxxx>
---

v3:
 * Drop revert no_kernel_mapping since it's already on the list [Mani]
 * kfree metadata from the branch for parity

 drivers/remoteproc/qcom_q6v5_mss.c | 48 ++++++++++++++++++++++++++----
 1 file changed, 42 insertions(+), 6 deletions(-)

diff --git a/drivers/remoteproc/qcom_q6v5_mss.c b/drivers/remoteproc/qcom_q6v5_mss.c
index e2f765f87ec9..e25d44e20ae7 100644
--- a/drivers/remoteproc/qcom_q6v5_mss.c
+++ b/drivers/remoteproc/qcom_q6v5_mss.c
@@ -215,6 +215,7 @@ struct q6v5 {
 	size_t mba_size;
 	size_t dp_size;
 
+	phys_addr_t mdata_phys;
 	phys_addr_t mpss_phys;
 	phys_addr_t mpss_reloc;
 	size_t mpss_size;
@@ -973,15 +974,29 @@ static int q6v5_mpss_init_image(struct q6v5 *qproc, const struct firmware *fw,
 	if (IS_ERR(metadata))
 		return PTR_ERR(metadata);
 
-	ptr = dma_alloc_attrs(qproc->dev, size, &phys, GFP_KERNEL, dma_attrs);
-	if (!ptr) {
-		kfree(metadata);
-		dev_err(qproc->dev, "failed to allocate mdt buffer\n");
-		return -ENOMEM;
+	if (qproc->mdata_phys) {
+		phys = qproc->mdata_phys;
+		ptr = memremap(qproc->mdata_phys, size, MEMREMAP_WC);
+		if (!ptr) {
+			kfree(metadata);
+			dev_err(qproc->dev, "unable to map memory region: %pa+%zx\n",
+				&qproc->mdata_phys, size);
+			return -EBUSY;
+		}
+	} else {
+		ptr = dma_alloc_attrs(qproc->dev, size, &phys, GFP_KERNEL, dma_attrs);
+		if (!ptr) {
+			kfree(metadata);
+			dev_err(qproc->dev, "failed to allocate mdt buffer\n");
+			return -ENOMEM;
+		}
 	}
 
 	memcpy(ptr, metadata, size);
 
+	if (qproc->mdata_phys)
+		memunmap(ptr);
+
 	/* Hypervisor mapping to access metadata by modem */
 	mdata_perm = BIT(QCOM_SCM_VMID_HLOS);
 	ret = q6v5_xfer_mem_ownership(qproc, &mdata_perm, false, true,
@@ -1010,7 +1025,8 @@ static int q6v5_mpss_init_image(struct q6v5 *qproc, const struct firmware *fw,
 			 "mdt buffer not reclaimed system may become unstable\n");
 
 free_dma_attrs:
-	dma_free_attrs(qproc->dev, size, ptr, phys, dma_attrs);
+	if (!qproc->mdata_phys)
+		dma_free_attrs(qproc->dev, size, ptr, phys, dma_attrs);
 	kfree(metadata);
 
 	return ret < 0 ? ret : 0;
@@ -1893,6 +1909,26 @@ static int q6v5_alloc_memory_region(struct q6v5 *qproc)
 	qproc->mpss_phys = qproc->mpss_reloc = r.start;
 	qproc->mpss_size = resource_size(&r);
 
+	if (!child) {
+		node = of_parse_phandle(qproc->dev->of_node, "memory-region", 2);
+	} else {
+		child = of_get_child_by_name(qproc->dev->of_node, "metadata");
+		node = of_parse_phandle(child, "memory-region", 0);
+		of_node_put(child);
+	}
+
+	if (!node)
+		return 0;
+
+	ret = of_address_to_resource(node, 0, &r);
+	of_node_put(node);
+	if (ret) {
+		dev_err(qproc->dev, "unable to resolve metadata region\n");
+		return ret;
+	}
+
+	qproc->mdata_phys = r.start;
+
 	return 0;
 }
 
-- 
2.17.1