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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-11 08:27:49 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-11 08:27:49 +0000 |
commit | ace9429bb58fd418f0c81d4c2835699bddf6bde6 (patch) | |
tree | b2d64bc10158fdd5497876388cd68142ca374ed3 /drivers/char/hw_random/arm_smccc_trng.c | |
parent | Initial commit. (diff) | |
download | linux-ace9429bb58fd418f0c81d4c2835699bddf6bde6.tar.xz linux-ace9429bb58fd418f0c81d4c2835699bddf6bde6.zip |
Adding upstream version 6.6.15.upstream/6.6.15
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'drivers/char/hw_random/arm_smccc_trng.c')
-rw-r--r-- | drivers/char/hw_random/arm_smccc_trng.c | 121 |
1 files changed, 121 insertions, 0 deletions
diff --git a/drivers/char/hw_random/arm_smccc_trng.c b/drivers/char/hw_random/arm_smccc_trng.c new file mode 100644 index 0000000000..7e954341b0 --- /dev/null +++ b/drivers/char/hw_random/arm_smccc_trng.c @@ -0,0 +1,121 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Randomness driver for the ARM SMCCC TRNG Firmware Interface + * https://developer.arm.com/documentation/den0098/latest/ + * + * Copyright (C) 2020 Arm Ltd. + * + * The ARM TRNG firmware interface specifies a protocol to read entropy + * from a higher exception level, to abstract from any machine specific + * implemenations and allow easier use in hypervisors. + * + * The firmware interface is realised using the SMCCC specification. + */ + +#include <linux/bits.h> +#include <linux/device.h> +#include <linux/hw_random.h> +#include <linux/module.h> +#include <linux/platform_device.h> +#include <linux/arm-smccc.h> + +#ifdef CONFIG_ARM64 +#define ARM_SMCCC_TRNG_RND ARM_SMCCC_TRNG_RND64 +#define MAX_BITS_PER_CALL (3 * 64UL) +#else +#define ARM_SMCCC_TRNG_RND ARM_SMCCC_TRNG_RND32 +#define MAX_BITS_PER_CALL (3 * 32UL) +#endif + +/* We don't want to allow the firmware to stall us forever. */ +#define SMCCC_TRNG_MAX_TRIES 20 + +#define SMCCC_RET_TRNG_INVALID_PARAMETER -2 +#define SMCCC_RET_TRNG_NO_ENTROPY -3 + +static int copy_from_registers(char *buf, struct arm_smccc_res *res, + size_t bytes) +{ + unsigned int chunk, copied; + + if (bytes == 0) + return 0; + + chunk = min(bytes, sizeof(long)); + memcpy(buf, &res->a3, chunk); + copied = chunk; + if (copied >= bytes) + return copied; + + chunk = min((bytes - copied), sizeof(long)); + memcpy(&buf[copied], &res->a2, chunk); + copied += chunk; + if (copied >= bytes) + return copied; + + chunk = min((bytes - copied), sizeof(long)); + memcpy(&buf[copied], &res->a1, chunk); + + return copied + chunk; +} + +static int smccc_trng_read(struct hwrng *rng, void *data, size_t max, bool wait) +{ + struct arm_smccc_res res; + u8 *buf = data; + unsigned int copied = 0; + int tries = 0; + + while (copied < max) { + size_t bits = min_t(size_t, (max - copied) * BITS_PER_BYTE, + MAX_BITS_PER_CALL); + + arm_smccc_1_1_invoke(ARM_SMCCC_TRNG_RND, bits, &res); + + switch ((int)res.a0) { + case SMCCC_RET_SUCCESS: + copied += copy_from_registers(buf + copied, &res, + bits / BITS_PER_BYTE); + tries = 0; + break; + case SMCCC_RET_TRNG_NO_ENTROPY: + if (!wait) + return copied; + tries++; + if (tries >= SMCCC_TRNG_MAX_TRIES) + return copied; + cond_resched(); + break; + default: + return -EIO; + } + } + + return copied; +} + +static int smccc_trng_probe(struct platform_device *pdev) +{ + struct hwrng *trng; + + trng = devm_kzalloc(&pdev->dev, sizeof(*trng), GFP_KERNEL); + if (!trng) + return -ENOMEM; + + trng->name = "smccc_trng"; + trng->read = smccc_trng_read; + + return devm_hwrng_register(&pdev->dev, trng); +} + +static struct platform_driver smccc_trng_driver = { + .driver = { + .name = "smccc_trng", + }, + .probe = smccc_trng_probe, +}; +module_platform_driver(smccc_trng_driver); + +MODULE_ALIAS("platform:smccc_trng"); +MODULE_AUTHOR("Andre Przywara"); +MODULE_LICENSE("GPL"); |