vc_screen: extract vcs_write_buf

This is the counterpart of the previous patch: here, we extract buffer
writing with attributes from vcs_write.

Now, there is no need for org to be initialized to NULL. The org0
check before update_region() confuses compilers, so check org instead.
It provides the same semantics. And it also eliminates the need for
initialization of org0.

We switch the branches of the attr 'if' too, as the inversion brings only
confusion now.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20200818085706.12163-8-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 92 insertions, 76 deletions

diff --git a/drivers/tty/vt/vc_screen.c b/drivers/tty/vt/vc_screen.c
index 62e6d240f0dd..10a26fd5f1b7 100644
--- a/drivers/tty/vt/vc_screen.c
+++ b/drivers/tty/vt/vc_screen.c
@@ -481,14 +481,93 @@ static u16 *vcs_write_buf_noattr(struct vc_data *vc, const char *con_buf,
 	return org;
 }
 
+static u16 *vcs_write_buf(struct vc_data *vc, const char *con_buf,
+		unsigned int pos, unsigned int count, bool viewed, u16 **org0)
+{
+	u16 *org;
+	unsigned int col, maxcol = vc->vc_cols;
+	unsigned char c;
+
+	/* header */
+	if (pos < HEADER_SIZE) {
+		char header[HEADER_SIZE];
+
+		getconsxy(vc, header + 2);
+		while (pos < HEADER_SIZE && count > 0) {
+			count--;
+			header[pos++] = *con_buf++;
+		}
+		if (!viewed)
+			putconsxy(vc, header + 2);
+	}
+
+	if (!count)
+		return NULL;
+
+	pos -= HEADER_SIZE;
+	col = (pos/2) % maxcol;
+
+	*org0 = org = screen_pos(vc, pos/2, viewed);
+
+	/* odd pos -- the first single character */
+	if (pos & 1) {
+		count--;
+		c = *con_buf++;
+#ifdef __BIG_ENDIAN
+		vcs_scr_writew(vc, c |
+		     (vcs_scr_readw(vc, org) & 0xff00), org);
+#else
+		vcs_scr_writew(vc, (c << 8) |
+		     (vcs_scr_readw(vc, org) & 0xff), org);
+#endif
+		org++;
+		pos++;
+		if (++col == maxcol) {
+			org = screen_pos(vc, pos/2, viewed);
+			col = 0;
+		}
+	}
+
+	pos /= 2;
+	pos += maxcol - col;
+
+	/* even pos -- handle attr+character pairs */
+	while (count > 1) {
+		unsigned short w;
+
+		w = get_unaligned(((unsigned short *)con_buf));
+		vcs_scr_writew(vc, w, org++);
+		con_buf += 2;
+		count -= 2;
+		if (++col == maxcol) {
+			org = screen_pos(vc, pos, viewed);
+			col = 0;
+			pos += maxcol;
+		}
+	}
+
+	if (!count)
+		return org;
+
+	/* odd pos -- the remaining character */
+	c = *con_buf++;
+#ifdef __BIG_ENDIAN
+	vcs_scr_writew(vc, (vcs_scr_readw(vc, org) & 0xff) | (c << 8), org);
+#else
+	vcs_scr_writew(vc, (vcs_scr_readw(vc, org) & 0xff00) | c, org);
+#endif
+
+	return org;
+}
+
 static ssize_t
 vcs_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
 {
 	struct inode *inode = file_inode(file);
 	struct vc_data *vc;
-	char *con_buf0, *con_buf;
-	u16 *org0 = NULL, *org = NULL;
-	unsigned int written, col, maxcol;
+	char *con_buf;
+	u16 *org0, *org;
+	unsigned int written;
 	int size;
 	ssize_t ret;
 	loff_t pos;
@@ -526,7 +605,7 @@ vcs_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
 		count = size - pos;
 	written = 0;
 	while (count) {
-		unsigned int orig_count, p, this_round = count;
+		unsigned int this_round = count;
 
 		if (this_round > CON_BUF_SIZE)
 			this_round = CON_BUF_SIZE;
@@ -571,81 +650,18 @@ vcs_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
 		 * under the lock using the local kernel buffer.
 		 */
 
-		if (!attr) {
+		if (attr)
+			org = vcs_write_buf(vc, con_buf, pos, this_round,
+					viewed, &org0);
+		else
 			org = vcs_write_buf_noattr(vc, con_buf, pos, this_round,
 					viewed, &org0);
-		} else {
-			con_buf0 = con_buf;
-			orig_count = this_round;
-			maxcol = vc->vc_cols;
-			p = pos;
-
-			if (p < HEADER_SIZE) {
-				char header[HEADER_SIZE];
-
-				getconsxy(vc, header + 2);
-				while (p < HEADER_SIZE && this_round > 0) {
-					this_round--;
-					header[p++] = *con_buf0++;
-				}
-				if (!viewed)
-					putconsxy(vc, header + 2);
-			}
-			p -= HEADER_SIZE;
-			col = (p/2) % maxcol;
-			if (this_round > 0) {
-				org0 = org = screen_pos(vc, p/2, viewed);
-				if ((p & 1) && this_round > 0) {
-					char c;
-
-					this_round--;
-					c = *con_buf0++;
-#ifdef __BIG_ENDIAN
-					vcs_scr_writew(vc, c |
-					     (vcs_scr_readw(vc, org) & 0xff00), org);
-#else
-					vcs_scr_writew(vc, (c << 8) |
-					     (vcs_scr_readw(vc, org) & 0xff), org);
-#endif
-					org++;
-					p++;
-					if (++col == maxcol) {
-						org = screen_pos(vc, p/2, viewed);
-						col = 0;
-					}
-				}
-				p /= 2;
-				p += maxcol - col;
-			}
-			while (this_round > 1) {
-				unsigned short w;
 
-				w = get_unaligned(((unsigned short *)con_buf0));
-				vcs_scr_writew(vc, w, org++);
-				con_buf0 += 2;
-				this_round -= 2;
-				if (++col == maxcol) {
-					org = screen_pos(vc, p, viewed);
-					col = 0;
-					p += maxcol;
-				}
-			}
-			if (this_round > 0) {
-				unsigned char c;
-
-				c = *con_buf0++;
-#ifdef __BIG_ENDIAN
-				vcs_scr_writew(vc, (vcs_scr_readw(vc, org) & 0xff) | (c << 8), org);
-#else
-				vcs_scr_writew(vc, (vcs_scr_readw(vc, org) & 0xff00) | c, org);
-#endif
-			}
-		}
-		count -= orig_count;
-		written += orig_count;
-		buf += orig_count;
-		pos += orig_count;
-		if (org0)
+		count -= this_round;
+		written += this_round;
+		buf += this_round;
+		pos += this_round;
+		if (org)
 			update_region(vc, (unsigned long)(org0), org - org0);
 	}
 	*ppos += written;