Re: [PATCH v4 2/2] crypto: stm32 - Support for STM32 CRYP crypto module

From: Neil Armstrong
Date: Thu Oct 19 2017 - 09:47:18 EST

On 19/10/2017 15:01, Fabien DESSENNE wrote:
> Hi Corentin
>
>
> Thank you for your comments. I will fix according to them. See also me
> answers/questions below
>
> While we are at it, do you plan to deliver a new version of the
> crypto_engine update? (I had to remove the AEAD part of this new driver
> since it depends on that pending update)
>
> BR
>
> Fabien
>
>
> On 19/10/17 12:34, Corentin Labbe wrote:
>> Hello
>>
>> I have some minor comment below
>>
>> On Thu, Oct 19, 2017 at 11:03:59AM +0200, Fabien Dessenne wrote:
>>> This module registers block cipher algorithms that make use of the
>>> STMicroelectronics STM32 crypto "CRYP1" hardware.
>>> The following algorithms are supported:
>>> - aes: ecb, cbc, ctr
>>> - des: ecb, cbc
>>> - tdes: ecb, cbc
>>>
>>> Signed-off-by: Fabien Dessennie <fabien.dessenne@xxxxxx>
>>> ---
>>> drivers/crypto/stm32/Kconfig | 9 +
>>> drivers/crypto/stm32/Makefile | 3 +-
>>> drivers/crypto/stm32/stm32-cryp.c | 1188 +++++++++++++++++++++++++++++++++++++
>>> 3 files changed, 1199 insertions(+), 1 deletion(-)
>>> create mode 100644 drivers/crypto/stm32/stm32-cryp.c
>>>
>>> diff --git a/drivers/crypto/stm32/Kconfig b/drivers/crypto/stm32/Kconfig
>>> index 602332e..61ef00b 100644
>>> --- a/drivers/crypto/stm32/Kconfig
>>> +++ b/drivers/crypto/stm32/Kconfig
>> [...]
>>> +/* Bit [0] encrypt / decrypt */
>>> +#define FLG_ENCRYPT BIT(0)
>>> +/* Bit [8..1] algo & operation mode */
>>> +#define FLG_AES BIT(1)
>>> +#define FLG_DES BIT(2)
>>> +#define FLG_TDES BIT(3)
>>> +#define FLG_ECB BIT(4)
>>> +#define FLG_CBC BIT(5)
>>> +#define FLG_CTR BIT(6)
>>> +/* Mode mask = bits [15..0] */
>>> +#define FLG_MODE_MASK GENMASK(15, 0)
>>> +
>>> +/* Registers */
>>> +#define CRYP_CR 0x00000000
>>> +#define CRYP_SR 0x00000004
>>> +#define CRYP_DIN 0x00000008
>>> +#define CRYP_DOUT 0x0000000C
>>> +#define CRYP_DMACR 0x00000010
>>> +#define CRYP_IMSCR 0x00000014
>>> +#define CRYP_RISR 0x00000018
>>> +#define CRYP_MISR 0x0000001C
>>> +#define CRYP_K0LR 0x00000020
>>> +#define CRYP_K0RR 0x00000024
>>> +#define CRYP_K1LR 0x00000028
>>> +#define CRYP_K1RR 0x0000002C
>>> +#define CRYP_K2LR 0x00000030
>>> +#define CRYP_K2RR 0x00000034
>>> +#define CRYP_K3LR 0x00000038
>>> +#define CRYP_K3RR 0x0000003C
>>> +#define CRYP_IV0LR 0x00000040
>>> +#define CRYP_IV0RR 0x00000044
>>> +#define CRYP_IV1LR 0x00000048
>>> +#define CRYP_IV1RR 0x0000004C
>>> +
>>> +/* Registers values */
>>> +#define CR_DEC_NOT_ENC 0x00000004
>>> +#define CR_TDES_ECB 0x00000000
>>> +#define CR_TDES_CBC 0x00000008
>>> +#define CR_DES_ECB 0x00000010
>>> +#define CR_DES_CBC 0x00000018
>>> +#define CR_AES_ECB 0x00000020
>>> +#define CR_AES_CBC 0x00000028
>>> +#define CR_AES_CTR 0x00000030
>>> +#define CR_AES_KP 0x00000038
>>> +#define CR_AES_UNKNOWN 0xFFFFFFFF
>>> +#define CR_ALGO_MASK 0x00080038
>>> +#define CR_DATA32 0x00000000
>>> +#define CR_DATA16 0x00000040
>>> +#define CR_DATA8 0x00000080
>>> +#define CR_DATA1 0x000000C0
>>> +#define CR_KEY128 0x00000000
>>> +#define CR_KEY192 0x00000100
>>> +#define CR_KEY256 0x00000200
>>> +#define CR_FFLUSH 0x00004000
>>> +#define CR_CRYPEN 0x00008000
>> Why not using BIT(x) ?
>
> Some values are not only 1 bit (then we may use BIT and BITGEN but this
> would be less readable), so I prefer to keep this values.

You can use GENMASK and the corresponding FIELD_PREP() and FIELD_GET().
It avoids manipulating the bits directly.

>
>> Why not using also directly FLG_XX since CR_XX are arbitray values ? like using instead CR_AES_CBC = FLG_AES | FLG_CBC
>
> The CR_ values are used to write in the registers. FLG_ are arbitraty
> values, so we cannot mix them.
>
>>
>> [...]
>>> +static inline void stm32_cryp_wait_enable(struct stm32_cryp *cryp)
>>> +{
>>> + while (stm32_cryp_read(cryp, CRYP_CR) & CR_CRYPEN)
>>> + cpu_relax();
>>> +}
>> This function is not used, so you could remove it
>>
>>> +
>>> +static inline void stm32_cryp_wait_busy(struct stm32_cryp *cryp)
>>> +{
>>> + while (stm32_cryp_read(cryp, CRYP_SR) & SR_BUSY)
>>> + cpu_relax();
>>> +}
>> No timeout ?
>>
>>
>>> +
>>> +static inline void stm32_cryp_wait_output(struct stm32_cryp *cryp)
>>> +{
>>> + while (!(stm32_cryp_read(cryp, CRYP_SR) & SR_OFNE))
>>> + cpu_relax();
>>> +}
>> This function is not used, so you could remove it
>>
>> [...]
>>> +static int stm32_cryp_check_aligned(struct scatterlist *sg, size_t total,
>>> + size_t align)
>>> +{
>>> + int len = 0;
>>> +
>>> + if (!total)
>>> + return 0;
>>> +
>>> + if (!IS_ALIGNED(total, align))
>>> + return -EINVAL;
>>> +
>>> + while (sg) {
>>> + if (!IS_ALIGNED(sg->offset, sizeof(u32)))
>>> + return -1;
>> -1 is not a good return value, prefer any -Exxxx
>>
>>> +
>>> + if (!IS_ALIGNED(sg->length, align))
>>> + return -1;
>>> +
>>> + len += sg->length;
>>> + sg = sg_next(sg);
>>> + }
>>> +
>>> + if (len != total)
>>> + return -1;
>> [...]
>>> +static int stm32_cryp_copy_sgs(struct stm32_cryp *cryp)
>>> +{
>>> + void *buf_in, *buf_out;
>>> + int pages, total_in, total_out;
>>> +
>>> + if (!stm32_cryp_check_io_aligned(cryp)) {
>>> + cryp->sgs_copied = 0;
>>> + return 0;
>>> + }
>>> +
>>> + total_in = ALIGN(cryp->total_in, cryp->hw_blocksize);
>>> + pages = total_in ? get_order(total_in) : 1;
>>> + buf_in = (void *)__get_free_pages(GFP_ATOMIC, pages);
>>> +
>>> + total_out = ALIGN(cryp->total_out, cryp->hw_blocksize);
>>> + pages = total_out ? get_order(total_out) : 1;
>>> + buf_out = (void *)__get_free_pages(GFP_ATOMIC, pages);
>>> +
>>> + if (!buf_in || !buf_out) {
>>> + pr_err("Couldn't allocate pages for unaligned cases.\n");
>> You must use dev_err() instead. without it, it will be hard to know which subsystem said that error message.
>>
>> [...]
>>> +static int stm32_cryp_cra_init(struct crypto_tfm *tfm)
>>> +{
>>> + tfm->crt_ablkcipher.reqsize = sizeof(struct stm32_cryp_reqctx);
>>> +
>>> + return 0;
>>> +}
>> You could simply remove this function
>
> I am not sure we can. Here we set reqsize.
> Most of the other drivers do the same, but maybe this is wrong everywhere.
> Could you give more details?
>
>>
>> [...]
>>> +
>>> +static void stm32_cryp_cra_exit(struct crypto_tfm *tfm)
>>> +{
>>> +}
>>> +
>>> +static int stm32_cryp_crypt(struct ablkcipher_request *req, unsigned long mode)
>>> +{
>>> + struct stm32_cryp_ctx *ctx = crypto_ablkcipher_ctx(
>>> + crypto_ablkcipher_reqtfm(req));
>>> + struct stm32_cryp_reqctx *rctx = ablkcipher_request_ctx(req);
>>> + struct stm32_cryp *cryp = stm32_cryp_find_dev(ctx);
>>> +
>>> + if (!cryp)
>>> + return -ENODEV;
>>> +
>>> + rctx->mode = mode;
>>> +
>>> + return crypto_transfer_cipher_request_to_engine(cryp->engine, req);
>>> +}
>>> +
>>> +static int stm32_cryp_setkey(struct crypto_ablkcipher *tfm, const u8 *key,
>>> + unsigned int keylen)
>>> +{
>>> + struct stm32_cryp_ctx *ctx = crypto_ablkcipher_ctx(tfm);
>>> +
>>> + memcpy(ctx->key, key, keylen);
>>> + ctx->keylen = keylen;
>> You never zeroize the key after request.
>>
>> [...]
>>> +static const struct of_device_id stm32_dt_ids[] = {
>>> + { .compatible = "st,stm32f756-cryp", },
>>> + {},
>>> +};
>>> +MODULE_DEVICE_TABLE(of, sti_dt_ids);
>>> +
>>> +static int stm32_cryp_probe(struct platform_device *pdev)
>>> +{
>>> + struct device *dev = &pdev->dev;
>>> + struct stm32_cryp *cryp;
>>> + struct resource *res;
>>> + struct reset_control *rst;
>>> + const struct of_device_id *match;
>>> + int irq, ret;
>>> +
>>> + cryp = devm_kzalloc(dev, sizeof(*cryp), GFP_KERNEL);
>>> + if (!cryp)
>>> + return -ENOMEM;
>>> +
>>> + match = of_match_device(stm32_dt_ids, dev);
>>> + if (!match)
>>> + return -ENODEV;
>> I think this test is unnecessary, at least it should be before the devm_kzalloc
>>
>> Regards
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