firmware: qcom: tzmem: enable SHM Bridge support

SHM Bridge is a safety mechanism allowing to limit the amount of memory
shared between the kernel and the TrustZone to regions explicitly marked
as such.

Add a variant of the tzmem allocator that configures the memory pools as
SHM bridges. It also enables the SHM bridge globally so non-SHM bridge
memory will no longer work with SCM calls.

If enabled at build-time, it will still be checked for availability at
run-time. If the architecture doesn't support SHM Bridge, the allocator
will fall back to the generic mode.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Tested-by: Andrew Halaney <ahalaney@redhat.com> # sc8280xp-lenovo-thinkpad-x13s
Tested-by: Deepti Jaggi <quic_djaggi@quicinc.com> #sa8775p-ride
Reviewed-by: Elliot Berman <quic_eberman@quicinc.com>
Link: https://lore.kernel.org/r/20240527-shm-bridge-v10-11-ce7afaa58d3a@linaro.org
Signed-off-by: Bjorn Andersson <andersson@kernel.org>

2 files changed, 88 insertions, 1 deletions

diff --git a/drivers/firmware/qcom/Kconfig b/drivers/firmware/qcom/Kconfig
index 4634f8cecc7b..7f6eb4174734 100644
--- a/drivers/firmware/qcom/Kconfig
+++ b/drivers/firmware/qcom/Kconfig
@@ -28,6 +28,16 @@ config QCOM_TZMEM_MODE_GENERIC
 	  Use the generic allocator mode. The memory is page-aligned, non-cachable
 	  and physically contiguous.
 
+config QCOM_TZMEM_MODE_SHMBRIDGE
+	bool "SHM Bridge"
+	help
+	  Use Qualcomm Shared Memory Bridge. The memory has the same alignment as
+	  in the 'Generic' allocator but is also explicitly marked as an SHM Bridge
+	  buffer.
+
+	  With this selected, all buffers passed to the TrustZone must be allocated
+	  using the TZMem allocator or else the TrustZone will refuse to use them.
+
 endchoice
 
 config QCOM_SCM_DOWNLOAD_MODE_DEFAULT
diff --git a/drivers/firmware/qcom/qcom_tzmem.c b/drivers/firmware/qcom/qcom_tzmem.c
index 3853385bf215..aab6376cade5 100644
--- a/drivers/firmware/qcom/qcom_tzmem.c
+++ b/drivers/firmware/qcom/qcom_tzmem.c
@@ -66,7 +66,84 @@ static void qcom_tzmem_cleanup_area(struct qcom_tzmem_area *area)
 
 }
 
-#endif /* CONFIG_QCOM_TZMEM_MODE_GENERIC */
+#elif IS_ENABLED(CONFIG_QCOM_TZMEM_MODE_SHMBRIDGE)
+
+#include <linux/firmware/qcom/qcom_scm.h>
+#include <linux/of.h>
+
+#define QCOM_SHM_BRIDGE_NUM_VM_SHIFT 9
+
+static bool qcom_tzmem_using_shm_bridge;
+
+/* List of machines that are known to not support SHM bridge correctly. */
+static const char *const qcom_tzmem_blacklist[] = {
+	"qcom,sc8180x",
+	NULL
+};
+
+static int qcom_tzmem_init(void)
+{
+	const char *const *platform;
+	int ret;
+
+	for (platform = qcom_tzmem_blacklist; *platform; platform++) {
+		if (of_machine_is_compatible(*platform))
+			goto notsupp;
+	}
+
+	ret = qcom_scm_shm_bridge_enable();
+	if (ret == -EOPNOTSUPP)
+		goto notsupp;
+
+	if (!ret)
+		qcom_tzmem_using_shm_bridge = true;
+
+	return ret;
+
+notsupp:
+	dev_info(qcom_tzmem_dev, "SHM Bridge not supported\n");
+	return 0;
+}
+
+static int qcom_tzmem_init_area(struct qcom_tzmem_area *area)
+{
+	u64 pfn_and_ns_perm, ipfn_and_s_perm, size_and_flags;
+	int ret;
+
+	if (!qcom_tzmem_using_shm_bridge)
+		return 0;
+
+	pfn_and_ns_perm = (u64)area->paddr | QCOM_SCM_PERM_RW;
+	ipfn_and_s_perm = (u64)area->paddr | QCOM_SCM_PERM_RW;
+	size_and_flags = area->size | (1 << QCOM_SHM_BRIDGE_NUM_VM_SHIFT);
+
+	u64 *handle __free(kfree) = kzalloc(sizeof(*handle), GFP_KERNEL);
+	if (!handle)
+		return -ENOMEM;
+
+	ret = qcom_scm_shm_bridge_create(qcom_tzmem_dev, pfn_and_ns_perm,
+					 ipfn_and_s_perm, size_and_flags,
+					 QCOM_SCM_VMID_HLOS, handle);
+	if (ret)
+		return ret;
+
+	area->priv = no_free_ptr(handle);
+
+	return 0;
+}
+
+static void qcom_tzmem_cleanup_area(struct qcom_tzmem_area *area)
+{
+	u64 *handle = area->priv;
+
+	if (!qcom_tzmem_using_shm_bridge)
+		return;
+
+	qcom_scm_shm_bridge_delete(qcom_tzmem_dev, *handle);
+	kfree(handle);
+}
+
+#endif /* CONFIG_QCOM_TZMEM_MODE_SHMBRIDGE */
 
 static int qcom_tzmem_pool_add_memory(struct qcom_tzmem_pool *pool,
 				      size_t size, gfp_t gfp)