[PATCH v4 1/3] fbcon: Include font geometry in the rotated font cache

[Yao Yiqi]

From: Yao Yiqi <yaoyiqi3@xxxxxxxxxx>

fbcon_rotate_font() caches a rotated copy of the console font and
skips the rebuild when the fontdata pointer and the rotation match.
Raw font data carries no geometry, though: width, height and
charcount live in vc->vc_font. fbcon_set_font() deduplicates uploads
by byte equality, so the same bytes re-uploaded with different
dimensions keep the fontdata pointer while the geometry changes, and
the early-out skips the rebuild.

The rotated cell size depends on the geometry (rotation swaps width
and height), so the stale buffer is indexed with the new cell size.
Re-uploading a 4x16 font as 16x8 on a CW-rotated console, for
example, doubles the rotated cell size and reads past the end of the
old buffer.

Record the geometry the buffer was built from and compare it in the
early-out. The pointer-only key used to be backed by an explicit
width check in the deduplication, which commit 1e3c49aa03fb
("lib/fonts: Compare font data for equality with font_data_is_equal()")
dropped.

Fixes: 6cc50e1c5b57 ("[PATCH] fbcon: Console Rotation - Add support to rotate font bitmap")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Yao Yiqi <yaoyiqi3@xxxxxxxxxx>
---
 drivers/video/fbdev/core/fbcon.h        | 9 ++++++---
 drivers/video/fbdev/core/fbcon_rotate.c | 9 ++++++++-
 2 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/drivers/video/fbdev/core/fbcon.h b/drivers/video/fbdev/core/fbcon.h
index 407d207b14f1..bfbd70f8b1cd 100644
--- a/drivers/video/fbdev/core/fbcon.h
+++ b/drivers/video/fbdev/core/fbcon.h
@@ -89,10 +89,13 @@ struct fbcon_par {
 	char  *cursor_data;
 #ifdef CONFIG_FRAMEBUFFER_CONSOLE_ROTATION
 	struct {
-		font_data_t *fontdata;  /* source font */
-		u8 *buf;                /* rotated glyphs */
+		font_data_t *fontdata;       /* source font */
+		u8 *buf;                     /* rotated glyphs */
 		size_t bufsize;
-		int buf_rotate;         /* rotation of buf */
+		int buf_rotate;              /* rotation of buf */
+		unsigned int buf_width;      /* geometry of source font */
+		unsigned int buf_height;
+		unsigned int buf_charcount;
 	} rotated;
 #endif
 	u8    *cursor_src;
diff --git a/drivers/video/fbdev/core/fbcon_rotate.c b/drivers/video/fbdev/core/fbcon_rotate.c
index 6cdbc96eeca6..660a3fa81bae 100644
--- a/drivers/video/fbdev/core/fbcon_rotate.c
+++ b/drivers/video/fbdev/core/fbcon_rotate.c
@@ -21,11 +21,18 @@ int fbcon_rotate_font(struct fb_info *info, struct vc_data *vc)
 	unsigned char *buf;
 	int ret;
 
-	if (par->p->fontdata == par->rotated.fontdata && par->rotate == par->rotated.buf_rotate)
+	if (par->p->fontdata == par->rotated.fontdata &&
+	    par->rotate == par->rotated.buf_rotate &&
+	    vc->vc_font.width == par->rotated.buf_width &&
+	    vc->vc_font.height == par->rotated.buf_height &&
+	    vc->vc_font.charcount == par->rotated.buf_charcount)
 		return 0;
 
 	par->rotated.fontdata = par->p->fontdata;
 	par->rotated.buf_rotate = par->rotate;
+	par->rotated.buf_width = vc->vc_font.width;
+	par->rotated.buf_height = vc->vc_font.height;
+	par->rotated.buf_charcount = vc->vc_font.charcount;
 
 	if (info->fbops->fb_sync)
 		info->fbops->fb_sync(info);
-- 
2.56.0