[PATCH 0/2] Fix ati-vga segfault with guest_hwcursor=true

[PATCH 0/2] Fix ati-vga segfault with guest_hwcursor=true

[BALATON Zoltan]

Small fix to avoid a segfault when using guest_hwcursor.

BALATON Zoltan (2):
  ati-vga: Simplify hw cursor drawing
  ati-vga: Do not access pixel outside the screen

 hw/display/ati.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

-- 
2.41.3

[PATCH 1/2] ati-vga: Simplify hw cursor drawing

[BALATON Zoltan]

Avoid calculating index at every step when we can just count the
position.

Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
---
 hw/display/ati.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/hw/display/ati.c b/hw/display/ati.c
index be41f2e0e2..7543065456 100644
--- a/hw/display/ati.c
+++ b/hw/display/ati.c
@@ -200,7 +200,7 @@ static void ati_cursor_draw_line(VGACommonState *vga, uint8_t *d, int scr_y)
     ATIVGAState *s = container_of(vga, ATIVGAState, vga);
     uint32_t srcoff;
     uint32_t *dp = (uint32_t *)d;
-    int i, j, h;
+    int i, j, h, idx = 0;
 
     if (!(s->regs.crtc_gen_cntl & CRTC2_CUR_EN) ||
         scr_y < vga->hw_cursor_y || scr_y >= vga->hw_cursor_y + 64 ||
@@ -215,10 +215,10 @@ static void ati_cursor_draw_line(VGACommonState *vga, uint8_t *d, int scr_y)
         uint32_t color;
         uint8_t abits = vga_read_byte(vga, srcoff + i);
         uint8_t xbits = vga_read_byte(vga, srcoff + i + 8);
-        for (j = 0; j < 8; j++, abits <<= 1, xbits <<= 1) {
+        for (j = 0; j < 8; j++, abits <<= 1, xbits <<= 1, idx++) {
             if (abits & BIT(7)) {
                 if (xbits & BIT(7)) {
-                    color = dp[i * 8 + j] ^ 0xffffffff; /* complement */
+                    color = dp[idx] ^ 0xffffffff; /* complement */
                 } else {
                     continue; /* transparent, no change */
                 }
@@ -226,10 +226,10 @@ static void ati_cursor_draw_line(VGACommonState *vga, uint8_t *d, int scr_y)
                 color = (xbits & BIT(7) ? s->regs.cur_color1 :
                                           s->regs.cur_color0) | 0xff000000;
             }
-            if (vga->hw_cursor_x + i * 8 + j >= h) {
+            if (vga->hw_cursor_x + idx >= h) {
                 return; /* end of screen, don't span to next line */
             }
-            dp[i * 8 + j] = color;
+            dp[idx] = color;
         }
     }
 }
-- 
2.41.3

Re: [PATCH 1/2] ati-vga: Simplify hw cursor drawing

[Chad Jablonski]

Reviewed-by: Chad Jablonski <chad@jablonski.xyz>

[PATCH 2/2] ati-vga: Do not access pixel outside the screen

[BALATON Zoltan]

We check end of screen before writing the pixel but before that
complement color also accesses screen pixel so we have to check before
that. This fixes a segmentation fault with guest_hwcursor when pointer
is partially out of screen at lower right corner.

Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
---
 hw/display/ati.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/hw/display/ati.c b/hw/display/ati.c
index 7543065456..9fb798b3e9 100644
--- a/hw/display/ati.c
+++ b/hw/display/ati.c
@@ -216,6 +216,9 @@ static void ati_cursor_draw_line(VGACommonState *vga, uint8_t *d, int scr_y)
         uint8_t abits = vga_read_byte(vga, srcoff + i);
         uint8_t xbits = vga_read_byte(vga, srcoff + i + 8);
         for (j = 0; j < 8; j++, abits <<= 1, xbits <<= 1, idx++) {
+            if (vga->hw_cursor_x + idx >= h) {
+                return; /* end of screen, don't span to next line */
+            }
             if (abits & BIT(7)) {
                 if (xbits & BIT(7)) {
                     color = dp[idx] ^ 0xffffffff; /* complement */
@@ -226,9 +229,6 @@ static void ati_cursor_draw_line(VGACommonState *vga, uint8_t *d, int scr_y)
                 color = (xbits & BIT(7) ? s->regs.cur_color1 :
                                           s->regs.cur_color0) | 0xff000000;
             }
-            if (vga->hw_cursor_x + idx >= h) {
-                return; /* end of screen, don't span to next line */
-            }
             dp[idx] = color;
         }
     }
-- 
2.41.3

Re: [PATCH 2/2] ati-vga: Do not access pixel outside the screen

[Chad Jablonski]

Reviewed-by: Chad Jablonski <chad@jablonski.xyz>