linux-kernel - [PATCH v2] crypto: hisilicon - allow smaller reads in debugfs

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Date:   Tue, 2 Jun 2020 16:54:09 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Zhou Wang <wangzhou1@...ilicon.com>,
        Shukun Tan <tanshukun1@...wei.com>
Cc:     Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org
Subject: [PATCH v2] crypto: hisilicon - allow smaller reads in debugfs

Originally this code rejected any read less than 256 bytes.  There
is no need for this artificial limit.  We should just use the normal
helper functions to read a string from the kernel.

Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
---
v2: Use simple_read_from_buffer().  The v1 was slightly half arsed
because I left the original check for:

	if (*pos)
		return 0;

So it could result in partial reads.  The new code means that if you
want to read the buffer one byte at a time, that's fine or if you want
to read it in one 256 byte chunk that's also fine.  Plus it deletes 21
lines of code and is a lot cleaner.

 drivers/crypto/hisilicon/qm.c | 33 ++++++---------------------------
 1 file changed, 6 insertions(+), 27 deletions(-)

diff --git a/drivers/crypto/hisilicon/qm.c b/drivers/crypto/hisilicon/qm.c
index 9bb263cec6c30..13ccb9e29a2e1 100644
--- a/drivers/crypto/hisilicon/qm.c
+++ b/drivers/crypto/hisilicon/qm.c
@@ -1064,19 +1064,10 @@ static ssize_t qm_cmd_read(struct file *filp, char __user *buffer,
 	char buf[QM_DBG_READ_LEN];
 	int len;
 
-	if (*pos)
-		return 0;
-
-	if (count < QM_DBG_READ_LEN)
-		return -ENOSPC;
+	len = scnprintf(buf, QM_DBG_READ_LEN, "%s\n",
+			"Please echo help to cmd to get help information");
 
-	len = snprintf(buf, QM_DBG_READ_LEN, "%s\n",
-		       "Please echo help to cmd to get help information");
-
-	if (copy_to_user(buffer, buf, len))
-		return -EFAULT;
-
-	return (*pos = len);
+	return simple_read_from_buffer(buffer, count, pos, buf, len);
 }
 
 static void *qm_ctx_alloc(struct hisi_qm *qm, size_t ctx_size,
@@ -2691,24 +2682,12 @@ static ssize_t qm_status_read(struct file *filp, char __user *buffer,
 {
 	struct hisi_qm *qm = filp->private_data;
 	char buf[QM_DBG_READ_LEN];
-	int val, cp_len, len;
-
-	if (*pos)
-		return 0;
-
-	if (count < QM_DBG_READ_LEN)
-		return -ENOSPC;
+	int val, len;
 
 	val = atomic_read(&qm->status.flags);
-	len = snprintf(buf, QM_DBG_READ_LEN, "%s\n", qm_s[val]);
-	if (!len)
-		return -EFAULT;
-
-	cp_len = copy_to_user(buffer, buf, len);
-	if (cp_len)
-		return -EFAULT;
+	len = scnprintf(buf, QM_DBG_READ_LEN, "%s\n", qm_s[val]);
 
-	return (*pos = len);
+	return simple_read_from_buffer(buffer, count, pos, buf, len);
 }
 
 static const struct file_operations qm_status_fops = {
-- 
2.26.2