AWS Graviton based systems provide an Arm SMC call in the vendor defined
hypervisor region to read random numbers from a TRNG and return them
to the guest.
Co-developed-by: Ron Rindjunsky <ronri...@amazon.com>
Signed-off-by: Ali Saidi <alisa...@amazon.com>
Signed-off-by: Ron Rindjunsky <ronri...@amazon.com>
---
MAINTAINERS | 6 ++
drivers/char/hw_random/Kconfig | 13 ++++
drivers/char/hw_random/Makefile | 1 +
drivers/char/hw_random/graviton-rng.c | 130 ++++++++++++++++++++++++++++++++++
4 files changed, 150 insertions(+)
create mode 100644 drivers/char/hw_random/graviton-rng.c
diff --git a/MAINTAINERS b/MAINTAINERS
index 005902ea1450..e9c490e3fd9d 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -2771,6 +2771,12 @@ S: Maintained
F: Documentation/devicetree/bindings/iio/adc/avia-hx711.txt
F: drivers/iio/adc/hx711.c
+AWS GRAVITON TRNG DRIVER
+M: Ali Saidi <alisa...@amazon.com>
+L: linux-arm-ker...@lists.infradead.org (moderated for non-subscribers)
+S: Supported
+F: drivers/char/hw_random/graviton-rng.c
+
AX.25 NETWORK LAYER
M: Ralf Baechle <r...@linux-mips.org>
L: linux-h...@vger.kernel.org
diff --git a/drivers/char/hw_random/Kconfig b/drivers/char/hw_random/Kconfig
index 25a7d8ffdb5d..7ca7386a1ac4 100644
--- a/drivers/char/hw_random/Kconfig
+++ b/drivers/char/hw_random/Kconfig
@@ -439,6 +439,19 @@ config HW_RANDOM_OPTEE
If unsure, say Y.
+config HW_RANDOM_GRAVITON
+ tristate "AWS Graviton Random Number Generator support"
+ depends on HW_RANDOM && ACPI && (ARM64 || COMPILE_TEST)
+ default HW_RANDOM
+ help
+ This driver provides kernel-side support for the Random Number
+ Generator SMC found on AWS Graviton systems.
+
+ To compile this driver as a module, choose M here: the
+ module will be called graviton-rng.
+
+ If unsure, say Y.
+
endif # HW_RANDOM
config UML_RANDOM
diff --git a/drivers/char/hw_random/Makefile b/drivers/char/hw_random/Makefile
index 7c9ef4a7667f..d1fa72670e98 100644
--- a/drivers/char/hw_random/Makefile
+++ b/drivers/char/hw_random/Makefile
@@ -39,3 +39,4 @@ obj-$(CONFIG_HW_RANDOM_MTK) += mtk-rng.o
obj-$(CONFIG_HW_RANDOM_S390) += s390-trng.o
obj-$(CONFIG_HW_RANDOM_KEYSTONE) += ks-sa-rng.o
obj-$(CONFIG_HW_RANDOM_OPTEE) += optee-rng.o
+obj-$(CONFIG_HW_RANDOM_GRAVITON) += graviton-rng.o
diff --git a/drivers/char/hw_random/graviton-rng.c
b/drivers/char/hw_random/graviton-rng.c
new file mode 100644
index 000000000000..898c8bb98a20
--- /dev/null
+++ b/drivers/char/hw_random/graviton-rng.c
@@ -0,0 +1,130 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * AWS Graviton TRNG driver
+ *
+ * Copyright (C) 2019 Amazon Corp.
+ */
+
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/platform_device.h>
+#include <linux/arm-smccc.h>
+#include <linux/device.h>
+#include <linux/hw_random.h>
+#include <linux/io.h>
+#include <linux/delay.h>
+#include <linux/acpi.h>
+#include <linux/psci.h>
+#include <linux/module.h>
+
+#define AWS_GRAVITON_UUID \
+ ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, ARM_SMCCC_SMC_32, \
+ ARM_SMCCC_OWNER_VENDOR_HV, 0xFF01)
+#define AWS_GRAVITON_GET_VER \
+ ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, ARM_SMCCC_SMC_32, \
+ ARM_SMCCC_OWNER_VENDOR_HV, 0xFF03)
+#define AWS_GRAVITON_GET_RND \
+ ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, ARM_SMCCC_SMC_64, \
+ ARM_SMCCC_OWNER_VENDOR_HV, 0)
+
+/**
+ * UID of the Graviton TRNG API: 1b64036c-badc-483e-99d23e283f067bdd
+ */
+#define GRVTN_TRNG_UUID_0 0x6c03641b
+#define GRVTN_TRNG_UUID_1 0x3e48dcba
+#define GRVTN_TRNG_UUID_2 0x283ed299
+#define GRVTN_TRNG_UUID_3 0xdd7b063f
+
+static void grvtn_smccc_conduit(u64 call_id, struct arm_smccc_res *res)
+{
+ if (acpi_psci_use_hvc())
+ arm_smccc_1_1_hvc(call_id, res);
+ else
+ arm_smccc_1_1_smc(call_id, res);
+}
+
+static int grvtn_trng_read(struct hwrng *trng, void *buf, size_t max, bool
wait)
+{
+ struct arm_smccc_res res;
+ int err = 0;
+ /* timeout after one waiting period */
+ int iter_remain = 2;
+ size_t count = max > sizeof(ulong) * 2 ? sizeof(ulong) * 2 : max;
+ size_t total = count;
+
+ do {
+ if (err && wait)
+ /* Nominal wait is 5us */
+ udelay(err);
+
+ grvtn_smccc_conduit(AWS_GRAVITON_GET_RND, &res);
+ err = (int) res.a0;
+
+ if (err < 0)
+ return err;
+
+ iter_remain--;
+ } while (iter_remain && err && wait);
+
+ if (err)
+ return 0;
+
+ if (count > sizeof(ulong)) {
+ memcpy(buf, &res.a1, sizeof(ulong));
+ count -= sizeof(ulong);
+ buf += sizeof(ulong);
+ }
+ memcpy(buf, &res.a2, count);
+ return total;
+}
+
+static int grvtn_trng_probe(struct platform_device *pdev)
+{
+ int err;
+ struct arm_smccc_res res;
+ static struct hwrng ops = {
+ .name = "graviton",
+ .read = grvtn_trng_read,
+ .quality = 1024, /* all bits are sourced from a HW TRNG */
+ };
+
+ grvtn_smccc_conduit(AWS_GRAVITON_UUID, &res);
+
+ if (res.a0 != GRVTN_TRNG_UUID_0 || res.a1 != GRVTN_TRNG_UUID_1 ||
+ res.a2 != GRVTN_TRNG_UUID_2 || res.a3 != GRVTN_TRNG_UUID_3) {
+ dev_err(&pdev->dev, "failed to match UUID\n");
+ return -ENXIO;
+ }
+
+ grvtn_smccc_conduit(AWS_GRAVITON_GET_VER, &res);
+ dev_info(&pdev->dev, "Graviton TRNG, SMC version %d.%d\n",
+ (u32)res.a0, (u32)res.a1);
+
+ platform_set_drvdata(pdev, &ops);
+ err = devm_hwrng_register(&pdev->dev, &ops);
+ if (err)
+ dev_err(&pdev->dev, "failed to register hwrng");
+ return err;
+}
+
+static const struct acpi_device_id grvtn_trng_acpi_match[] = {
+ { "AMZN0010", },
+ {}
+};
+
+MODULE_DEVICE_TABLE(acpi, grvtn_trng_acpi_match);
+
+static struct platform_driver grvtn_trng_driver = {
+ .probe = grvtn_trng_probe,
+ .driver = {
+ .name = "graviton-rng",
+ .owner = THIS_MODULE,
+ .acpi_match_table = ACPI_PTR(grvtn_trng_acpi_match),
+ },
+};
+
+module_platform_driver(grvtn_trng_driver);
+
+MODULE_AUTHOR("Amazon.com, Inc. or it's affiliates");
+MODULE_DESCRIPTION("Graviton TRNG driver");
+MODULE_LICENSE("GPL v2");
--
2.15.3.AMZN
