LinuxKPI: Use simple_read_from_buffer in simple_attr_read and seq_read

Reviewed by:	bz
Sponsored by:	AFRL, DARPA
Differential Revision:	https://reviews.freebsd.org/D55879

sys/compat/linuxkpi/common/src/linux_seq_file.c

@@ -60,15 +60,8 @@ seq_read(struct linux_file *f, char *ubuf, size_t size, off_t *ppos)
 	if (rc)
 		return (rc);
 
-	rc = sbuf_len(sbuf);
-	if (*ppos >= rc || size < 1)
-		return (-EINVAL);
-
-	size = min(rc - *ppos, size);
-	memcpy(ubuf, sbuf_data(sbuf) + *ppos, size);
-	*ppos += size;
-
-	return (size);
+	return (simple_read_from_buffer(ubuf, size, ppos, sbuf_data(sbuf),
+	    sbuf_len(sbuf)));
 }
 
 int

sys/compat/linuxkpi/common/src/linux_simple_attr.c

@@ -119,18 +119,9 @@ simple_attr_read(struct file *filp, char *buf, size_t read_size, loff_t *ppos)
 
 	scnprintf(prebuf, sizeof(prebuf), sattr->fmt, data);
 
-	ret = strlen(prebuf) + 1;
-	if (*ppos >= ret || read_size < 1) {
-		ret = -EINVAL;
-		goto unlock;
-	}
-
-	read_size = min(ret - *ppos, read_size);
-	ret = strscpy(buf, prebuf + *ppos, read_size);
-
 	/* add 1 for null terminator */
-	if (ret > 0)
-		ret += 1;
+	ret = simple_read_from_buffer(buf, read_size, ppos, prebuf,
+	    strlen(prebuf) + 1);
 
 unlock:
 	mutex_unlock(&sattr->mutex);