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https://github.com/AsahiLinux/u-boot
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208 lines
5.3 KiB
C
208 lines
5.3 KiB
C
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// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright (c) 2022, Linaro Limited
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*/
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#define LOG_CATEGORY UCLASS_RNG
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#include <common.h>
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#include <dm.h>
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#include <linker_lists.h>
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#include <log.h>
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#include <rng.h>
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#include <dm/device_compat.h>
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#include <linux/arm-smccc.h>
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#include <linux/bitops.h>
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#include <linux/kernel.h>
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#include <linux/psci.h>
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#define DRIVER_NAME "smccc-trng"
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/**
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* Arm SMCCC TRNG firmware interface specification:
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* https://developer.arm.com/documentation/den0098/latest/
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*/
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#define ARM_SMCCC_TRNG_VERSION 0x84000050
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#define ARM_SMCCC_TRNG_FEATURES 0x84000051
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#define ARM_SMCCC_TRNG_GET_UUID 0x84000052
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#define ARM_SMCCC_TRNG_RND_32 0x84000053
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#define ARM_SMCCC_TRNG_RND_64 0xC4000053
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#define ARM_SMCCC_RET_TRNG_SUCCESS ((ulong)0)
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#define ARM_SMCCC_RET_TRNG_NOT_SUPPORTED ((ulong)-1)
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#define ARM_SMCCC_RET_TRNG_INVALID_PARAMETER ((ulong)-2)
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#define ARM_SMCCC_RET_TRNG_NO_ENTROPY ((ulong)-3)
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#define TRNG_MAJOR_MASK GENMASK(30, 16)
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#define TRNG_MAJOR_SHIFT 16
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#define TRNG_MINOR_MASK GENMASK(15, 0)
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#define TRNG_MINOR_SHIFT 0
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#define TRNG_MAX_RND_64 (192 / 8)
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#define TRNG_MAX_RND_32 (96 / 8)
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/**
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* struct smccc_trng_priv - Private data for SMCCC TRNG support
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*
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* @smc64 - True if TRNG_RND_64 is supported, false if TRNG_RND_32 is supported
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*/
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struct smccc_trng_priv {
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bool smc64;
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};
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/*
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* Copy random bytes from ulong SMCCC output register to target buffer
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* Defines 2 function flavors for whether ARM_SMCCC_TRNG_RND_32 or
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* ARM_SMCCC_TRNG_RND_64 was used to invoke the service.
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*/
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static size_t smc32_copy_sample(u8 **ptr, size_t size, ulong *rnd)
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{
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size_t len = min(size, sizeof(u32));
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u32 sample = *rnd;
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memcpy(*ptr, &sample, len);
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*ptr += len;
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return size - len;
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}
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static size_t smc64_copy_sample(u8 **ptr, size_t size, ulong *rnd)
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{
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size_t len = min(size, sizeof(u64));
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u64 sample = *rnd;
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memcpy(*ptr, &sample, len);
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*ptr += len;
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return size - len;
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}
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static int smccc_trng_read(struct udevice *dev, void *data, size_t len)
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{
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struct psci_plat_data *smccc = dev_get_parent_plat(dev);
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struct smccc_trng_priv *priv = dev_get_priv(dev);
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struct arm_smccc_res res;
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u32 func_id;
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u8 *ptr = data;
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size_t rem = len;
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size_t max_sz;
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size_t (*copy_sample)(u8 **ptr, size_t size, ulong *rnd);
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if (priv->smc64) {
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copy_sample = smc64_copy_sample;
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func_id = ARM_SMCCC_TRNG_RND_64;
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max_sz = TRNG_MAX_RND_64;
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} else {
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copy_sample = smc32_copy_sample;
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func_id = ARM_SMCCC_TRNG_RND_32;
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max_sz = TRNG_MAX_RND_32;
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}
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while (rem) {
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size_t sz = min(rem, max_sz);
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smccc->invoke_fn(func_id, sz * 8, 0, 0, 0, 0, 0, 0, &res);
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switch (res.a0) {
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case ARM_SMCCC_RET_TRNG_SUCCESS:
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break;
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case ARM_SMCCC_RET_TRNG_NO_ENTROPY:
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continue;
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default:
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return -EIO;
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}
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rem -= sz;
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sz = copy_sample(&ptr, sz, &res.a3);
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if (sz)
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sz = copy_sample(&ptr, sz, &res.a2);
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if (sz)
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sz = copy_sample(&ptr, sz, &res.a1);
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}
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return 0;
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}
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static const struct dm_rng_ops smccc_trng_ops = {
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.read = smccc_trng_read,
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};
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static bool smccc_trng_is_supported(void (*invoke_fn)(unsigned long a0, unsigned long a1,
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unsigned long a2, unsigned long a3,
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unsigned long a4, unsigned long a5,
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unsigned long a6, unsigned long a7,
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struct arm_smccc_res *res))
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{
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struct arm_smccc_res res;
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(*invoke_fn)(ARM_SMCCC_ARCH_FEATURES, ARM_SMCCC_TRNG_VERSION, 0, 0, 0, 0, 0, 0, &res);
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if (res.a0 == ARM_SMCCC_RET_NOT_SUPPORTED)
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return false;
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(*invoke_fn)(ARM_SMCCC_TRNG_VERSION, 0, 0, 0, 0, 0, 0, 0, &res);
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if (res.a0 & BIT(31))
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return false;
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/* Test 64bit interface and fallback to 32bit interface */
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invoke_fn(ARM_SMCCC_TRNG_FEATURES, ARM_SMCCC_TRNG_RND_64,
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0, 0, 0, 0, 0, 0, &res);
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if (res.a0 == ARM_SMCCC_RET_TRNG_NOT_SUPPORTED)
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invoke_fn(ARM_SMCCC_TRNG_FEATURES, ARM_SMCCC_TRNG_RND_32,
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0, 0, 0, 0, 0, 0, &res);
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return res.a0 == ARM_SMCCC_RET_TRNG_SUCCESS;
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}
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ARM_SMCCC_FEATURE_DRIVER(smccc_trng) = {
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.driver_name = DRIVER_NAME,
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.is_supported = smccc_trng_is_supported,
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};
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static int smccc_trng_probe(struct udevice *dev)
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{
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struct psci_plat_data *smccc = dev_get_parent_plat(dev);
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struct smccc_trng_priv *priv = dev_get_priv(dev);
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struct arm_smccc_res res;
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if (!(smccc_trng_is_supported(smccc->invoke_fn)))
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return -ENODEV;
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/* At least one of 64bit and 32bit interfaces is available */
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smccc->invoke_fn(ARM_SMCCC_TRNG_FEATURES, ARM_SMCCC_TRNG_RND_64,
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0, 0, 0, 0, 0, 0, &res);
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priv->smc64 = (res.a0 == ARM_SMCCC_RET_TRNG_SUCCESS);
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#ifdef DEBUG
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smccc->invoke_fn(ARM_SMCCC_TRNG_GET_UUID, 0, 0, 0, 0, 0, 0, 0, &res);
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if (res.a0 != ARM_SMCCC_RET_TRNG_NOT_SUPPORTED) {
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unsigned long uuid_a0 = res.a0;
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unsigned long uuid_a1 = res.a1;
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unsigned long uuid_a2 = res.a2;
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unsigned long uuid_a3 = res.a3;
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unsigned long major, minor;
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smccc->invoke_fn(ARM_SMCCC_TRNG_VERSION, 0, 0, 0, 0, 0, 0, 0, &res);
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major = (res.a0 & TRNG_MAJOR_MASK) >> TRNG_MAJOR_SHIFT;
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minor = (res.a0 & TRNG_MINOR_MASK) >> TRNG_MINOR_SHIFT;
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dev_dbg(dev, "Version %lu.%lu, UUID %08lx-%04lx-%04lx-%04lx-%04lx%08lx\n",
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major, minor, uuid_a0, uuid_a1 >> 16, uuid_a1 & GENMASK(16, 0),
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uuid_a2 >> 16, uuid_a2 & GENMASK(16, 0), uuid_a3);
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} else {
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dev_warn(dev, "Can't get TRNG UUID\n");
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}
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#endif
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return 0;
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}
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U_BOOT_DRIVER(smccc_trng) = {
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.name = DRIVER_NAME,
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.id = UCLASS_RNG,
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.ops = &smccc_trng_ops,
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.probe = smccc_trng_probe,
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.priv_auto = sizeof(struct smccc_trng_priv),
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};
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