[PATCH v8 10/12] firmware: qcom: tzmem: enable SHM Bridge support

Bartosz Golaszewski
2024-03-03T15:01:34Z

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>
---
drivers/firmware/qcom/Kconfig | 10 +++++
drivers/firmware/qcom/qcom_tzmem.c | 65 +++++++++++++++++++++++++++++-
2 files changed, 74 insertions(+), 1 deletion(-)

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 23f364afa6ca..244615e8c505 100644
--- a/drivers/firmware/qcom/qcom_tzmem.c
+++ b/drivers/firmware/qcom/qcom_tzmem.c
@@ -67,7 +67,70 @@ 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>
+
+#define QCOM_SHM_BRIDGE_NUM_VM_SHIFT 9
+
+static bool qcom_tzmem_using_shm_bridge;
+
+static int qcom_tzmem_init(void)
+{
+ int ret;
+
+ ret = qcom_scm_shm_bridge_enable();
+ if (ret == -EOPNOTSUPP) {
+ dev_info(qcom_tzmem_dev, "SHM Bridge not supported\n");
+ return 0;
+ }
+
+ if (!ret)
+ qcom_tzmem_using_shm_bridge = true;
+
+ return ret;
+}
+
+static int qcom_tzmem_init_area(struct qcom_tzmem_area *area)
+{
+ u64 pfn_and_ns_perm, ipfn_and_s_perm, size_and_flags, ns_perms;
+ int ret;
+
+ if (!qcom_tzmem_using_shm_bridge)
+ return 0;
+
+ ns_perms = (QCOM_SCM_PERM_WRITE | QCOM_SCM_PERM_READ);
+ pfn_and_ns_perm = (u64)area->paddr | ns_perms;
+ ipfn_and_s_perm = (u64)area->paddr | ns_perms;
+ 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)
--
2.40.1