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From:   Sean Anderson <sean.anderson@seco.com>
Subject: Re: [PATCH v2 2/2] crypto: mxs_dcp: Use sg_mapping_iter to copy data
To:     Richard Weinberger <richard@nod.at>
Cc:     Linux Crypto Mailing List <linux-crypto@vger.kernel.org>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        davem <davem@davemloft.net>, horia geanta <horia.geanta@nxp.com>,
        aymen sghaier <aymen.sghaier@nxp.com>,
        linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
        Marek Vasut <marex@denx.de>, david <david@sigma-star.at>
References: <20210701185638.3437487-1-sean.anderson@seco.com>
 <20210701185638.3437487-3-sean.anderson@seco.com>
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On 7/1/21 3:59 PM, Richard Weinberger wrote:
> ----- Ursprüngliche Mail -----
>> Von: "Sean Anderson" <sean.anderson@seco.com>
>> An: "Linux Crypto Mailing List" <linux-crypto@vger.kernel.org>, "Herbert Xu" <herbert@gondor.apana.org.au>, "davem"
>> <davem@davemloft.net>
>> CC: "horia geanta" <horia.geanta@nxp.com>, "aymen sghaier" <aymen.sghaier@nxp.com>, "richard" <richard@nod.at>,
>> "linux-arm-kernel" <linux-arm-kernel@lists.infradead.org>, "Marek Vasut" <marex@denx.de>, "Sean Anderson"
>> <sean.anderson@seco.com>
>> Gesendet: Donnerstag, 1. Juli 2021 20:56:38
>> Betreff: [PATCH v2 2/2] crypto: mxs_dcp: Use sg_mapping_iter to copy data
>
>> This uses the sg_miter_*() functions to copy data, instead of doing it
>> ourselves. Using sg_copy_buffer() would be better, but this way we don't
>> have to keep traversing the beginning of the scatterlist every time we
>> do another copy.
>
> Huh? This does not match the code.
> You use sg_pcopy_from_buffer() which is just a wrapper around sg_copy_buffer().
>
> Did you forget to update the commit message? :-)

Yes I did. I ran into trouble with sg_miter_* since there is no way to
consume only part of a page (without touching the "internal" members of
the iter).

--Sean

>
>> In addition to reducing code size, this fixes the following oops
>> resulting from failing to kmap the page:
>>
>> [   68.896381] Unable to handle kernel NULL pointer dereference at virtual
>> address 00000ab8
>> [   68.904539] pgd = 3561adb3
>> [   68.907475] [00000ab8] *pgd=00000000
>> [   68.911153] Internal error: Oops: 805 [#1] ARM
>> [   68.915618] Modules linked in: cfg80211 rfkill des_generic libdes arc4
>> libarc4 cbc ecb algif_skcipher sha256_generic libsha256 sha1_generic hmac
>> aes_generic libaes cmac sha512_generic md5 md4 algif_hash af_alg i2c_imx
>> i2c_core ci_hdrc_imx ci_hdrc mxs_dcp ulpi roles udc_core imx_sdma usbmisc_imx
>> usb_common firmware_class virt_dma phy_mxs_usb nf_tables nfnetlink ip_tables
>> x_tables ipv6 autofs4
>> [   68.950741] CPU: 0 PID: 139 Comm: mxs_dcp_chan/ae Not tainted 5.10.34 #296
>> [   68.958501] Hardware name: Freescale i.MX6 Ultralite (Device Tree)
>> [   68.964710] PC is at memcpy+0xa8/0x330
>> [   68.968479] LR is at 0xd7b2bc9d
>> [   68.971638] pc : [<c053e7c8>]    lr : [<d7b2bc9d>]    psr: 000f0013
>> [   68.977920] sp : c2cbbee4  ip : 00000010  fp : 00000010
>> [   68.983159] r10: 00000000  r9 : c3283a40  r8 : 1a5a6f08
>> [   68.988402] r7 : 4bfe0ecc  r6 : 76d8a220  r5 : c32f9050  r4 : 00000001
>> [   68.994945] r3 : 00000ab8  r2 : fffffff0  r1 : c32f9050  r0 : 00000ab8
>> [   69.001492] Flags: nzcv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment none
>> [   69.008646] Control: 10c53c7d  Table: 83664059  DAC: 00000051
>> [   69.014414] Process mxs_dcp_chan/ae (pid: 139, stack limit = 0x667b57ab)
>> [   69.021133] Stack: (0xc2cbbee4 to 0xc2cbc000)
>> [   69.025519] bee0:          c32f9050 c3235408 00000010 00000010 00000ab8
>> 00000001 bf10406c
>> [   69.033720] bf00: 00000000 00000000 00000010 00000000 c32355d0 832fb080
>> 00000000 c13de2fc
>> [   69.041921] bf20: c3628010 00000010 c33d5780 00000ab8 bf1067e8 00000002
>> c21e5010 c2cba000
>> [   69.050125] bf40: c32f8040 00000000 bf106a40 c32f9040 c3283a80 00000001
>> bf105240 c3234040
>> [   69.058327] bf60: ffffe000 c3204100 c2c69800 c2cba000 00000000 bf103b84
>> 00000000 c2eddc54
>> [   69.066530] bf80: c3204144 c0140d1c c2cba000 c2c69800 c0140be8 00000000
>> 00000000 00000000
>> [   69.074730] bfa0: 00000000 00000000 00000000 c0100114 00000000 00000000
>> 00000000 00000000
>> [   69.082932] bfc0: 00000000 00000000 00000000 00000000 00000000 00000000
>> 00000000 00000000
>> [   69.091131] bfe0: 00000000 00000000 00000000 00000000 00000013 00000000
>> 00000000 00000000
>> [   69.099364] [<c053e7c8>] (memcpy) from [<bf10406c>]
>> (dcp_chan_thread_aes+0x4e8/0x840 [mxs_dcp])
>> [   69.108117] [<bf10406c>] (dcp_chan_thread_aes [mxs_dcp]) from [<c0140d1c>]
>> (kthread+0x134/0x160)
>> [   69.116941] [<c0140d1c>] (kthread) from [<c0100114>]
>> (ret_from_fork+0x14/0x20)
>> [   69.124178] Exception stack(0xc2cbbfb0 to 0xc2cbbff8)
>> [   69.129250] bfa0:                                     00000000 00000000
>> 00000000 00000000
>> [   69.137450] bfc0: 00000000 00000000 00000000 00000000 00000000 00000000
>> 00000000 00000000
>> [   69.145648] bfe0: 00000000 00000000 00000000 00000000 00000013 00000000
>> [   69.152289] Code: e320f000 e4803004 e4804004 e4805004 (e4806004)
>>
>> Signed-off-by: Sean Anderson <sean.anderson@seco.com>
>> ---
>>
>> Changes in v2:
>> - Fix warning when taking the minimum of a u32 and a size_t
>> - Use sg_pcopy_from_buffer to properly deal with partial reads.
>>
>> drivers/crypto/mxs-dcp.c | 36 +++++++++---------------------------
>> 1 file changed, 9 insertions(+), 27 deletions(-)
>>
>> diff --git a/drivers/crypto/mxs-dcp.c b/drivers/crypto/mxs-dcp.c
>> index f397cc5bf102..d19e5ffb5104 100644
>> --- a/drivers/crypto/mxs-dcp.c
>> +++ b/drivers/crypto/mxs-dcp.c
>> @@ -300,21 +300,20 @@ static int mxs_dcp_aes_block_crypt(struct
>> crypto_async_request *arq)
>>
>> 	struct scatterlist *dst = req->dst;
>> 	struct scatterlist *src = req->src;
>> -	const int nents = sg_nents(req->src);
>> +	int dst_nents = sg_nents(dst);
>>
>> 	const int out_off = DCP_BUF_SZ;
>> 	uint8_t *in_buf = sdcp->coh->aes_in_buf;
>> 	uint8_t *out_buf = sdcp->coh->aes_out_buf;
>>
>> -	uint8_t *out_tmp, *src_buf, *dst_buf = NULL;
>> 	uint32_t dst_off = 0;
>> +	uint8_t *src_buf = NULL;
>> 	uint32_t last_out_len = 0;
>>
>> 	uint8_t *key = sdcp->coh->aes_key;
>>
>> 	int ret = 0;
>> -	int split = 0;
>> -	unsigned int i, len, clen, rem = 0, tlen = 0;
>> +	unsigned int i, len, clen, tlen = 0;
>> 	int init = 0;
>> 	bool limit_hit = false;
>>
>> @@ -332,7 +331,7 @@ static int mxs_dcp_aes_block_crypt(struct
>> crypto_async_request *arq)
>> 		memset(key + AES_KEYSIZE_128, 0, AES_KEYSIZE_128);
>> 	}
>>
>> -	for_each_sg(req->src, src, nents, i) {
>> +	for_each_sg(req->src, src, sg_nents(src), i) {
>> 		src_buf = sg_virt(src);
>> 		len = sg_dma_len(src);
>> 		tlen += len;
>> @@ -357,34 +356,17 @@ static int mxs_dcp_aes_block_crypt(struct
>> crypto_async_request *arq)
>> 			 * submit the buffer.
>> 			 */
>> 			if (actx->fill == out_off || sg_is_last(src) ||
>> -				limit_hit) {
>> +			    limit_hit) {
>> 				ret = mxs_dcp_run_aes(actx, req, init);
>> 				if (ret)
>> 					return ret;
>> 				init = 0;
>>
>> -				out_tmp = out_buf;
>> +				sg_pcopy_from_buffer(dst, dst_nents, out_buf,
>> +						     actx->fill, dst_off);
>> +				dst_off += actx->fill;
>> 				last_out_len = actx->fill;
>> -				while (dst && actx->fill) {
>> -					if (!split) {
>> -						dst_buf = sg_virt(dst);
>> -						dst_off = 0;
>> -					}
>> -					rem = min(sg_dma_len(dst) - dst_off,
>> -						  actx->fill);
>> -
>> -					memcpy(dst_buf + dst_off, out_tmp, rem);
>> -					out_tmp += rem;
>> -					dst_off += rem;
>> -					actx->fill -= rem;
>> -
>> -					if (dst_off == sg_dma_len(dst)) {
>> -						dst = sg_next(dst);
>> -						split = 0;
>> -					} else {
>> -						split = 1;
>> -					}
>> -				}
>> +				actx->fill = 0;
>> 			}
>> 		} while (len);
>>
>> --
>> 2.25.1
>