From 2f57a288065de4fffcf182deacd3c75aec90a9ef Mon Sep 17 00:00:00 2001
From: BALATON Zoltan <balaton@eik.bme.hu>
Date: Thu, 21 May 2020 21:39:44 +0200
Subject: [PATCH] sm501: Replace hand written implementation with pixman where
 possible

Besides being faster this should also prevent malicious guests to
abuse 2D engine to overwrite data or cause a crash.

Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
Message-id: 58666389b6cae256e4e972a32c05cf8aa51bffc0.1590089984.git.balaton@eik.bme.hu
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
---
 hw/display/sm501.c | 207 ++++++++++++++++++++++++++-------------------
 1 file changed, 119 insertions(+), 88 deletions(-)

diff --git a/hw/display/sm501.c b/hw/display/sm501.c
index 98b3b97f7b..7dc4bb18b7 100644
--- a/hw/display/sm501.c
+++ b/hw/display/sm501.c
@@ -706,13 +706,12 @@ static void sm501_2d_operation(SM501State *s)
     /* 1 if rop2 source is the pattern, otherwise the source is the bitmap */
     int rop2_source_is_pattern = (s->twoD_control >> 14) & 0x1;
     int rop = s->twoD_control & 0xFF;
-    int dst_x = (s->twoD_destination >> 16) & 0x01FFF;
-    int dst_y = s->twoD_destination & 0xFFFF;
-    int width = (s->twoD_dimension >> 16) & 0x1FFF;
-    int height = s->twoD_dimension & 0xFFFF;
+    unsigned int dst_x = (s->twoD_destination >> 16) & 0x01FFF;
+    unsigned int dst_y = s->twoD_destination & 0xFFFF;
+    unsigned int width = (s->twoD_dimension >> 16) & 0x1FFF;
+    unsigned int height = s->twoD_dimension & 0xFFFF;
     uint32_t dst_base = s->twoD_destination_base & 0x03FFFFFF;
-    uint8_t *dst = s->local_mem + dst_base;
-    int dst_pitch = (s->twoD_pitch >> 16) & 0x1FFF;
+    unsigned int dst_pitch = (s->twoD_pitch >> 16) & 0x1FFF;
     int crt = (s->dc_crt_control & SM501_DC_CRT_CONTROL_SEL) ? 1 : 0;
     int fb_len = get_width(s, crt) * get_height(s, crt) * get_bpp(s, crt);
 
@@ -721,104 +720,136 @@ static void sm501_2d_operation(SM501State *s)
         return;
     }
 
-    if (rop_mode == 0) {
-        if (rop != 0xcc) {
-            /* Anything other than plain copies are not supported */
-            qemu_log_mask(LOG_UNIMP, "sm501: rop3 mode with rop %x is not "
-                          "supported.\n", rop);
-        }
-    } else {
-        if (rop2_source_is_pattern && rop != 0x5) {
-            /* For pattern source, we support only inverse dest */
-            qemu_log_mask(LOG_UNIMP, "sm501: rop2 source being the pattern and "
-                          "rop %x is not supported.\n", rop);
-        } else {
-            if (rop != 0x5 && rop != 0xc) {
-                /* Anything other than plain copies or inverse dest is not
-                 * supported */
-                qemu_log_mask(LOG_UNIMP, "sm501: rop mode %x is not "
-                              "supported.\n", rop);
-            }
-        }
-    }
-
     if (s->twoD_source_base & BIT(27) || s->twoD_destination_base & BIT(27)) {
         qemu_log_mask(LOG_UNIMP, "sm501: only local memory is supported.\n");
         return;
     }
 
+    if (!dst_pitch) {
+        qemu_log_mask(LOG_GUEST_ERROR, "sm501: Zero dest pitch.\n");
+        return;
+    }
+
+    if (!width || !height) {
+        qemu_log_mask(LOG_GUEST_ERROR, "sm501: Zero size 2D op.\n");
+        return;
+    }
+
+    if (rtl) {
+        dst_x -= width - 1;
+        dst_y -= height - 1;
+    }
+
+    if (dst_base >= get_local_mem_size(s) || dst_base +
+        (dst_x + width + (dst_y + height) * (dst_pitch + width)) *
+        (1 << format) >= get_local_mem_size(s)) {
+        qemu_log_mask(LOG_GUEST_ERROR, "sm501: 2D op dest is outside vram.\n");
+        return;
+    }
+
     switch (cmd) {
-    case 0x00: /* copy area */
+    case 0: /* BitBlt */
     {
-        int src_x = (s->twoD_source >> 16) & 0x01FFF;
-        int src_y = s->twoD_source & 0xFFFF;
+        unsigned int src_x = (s->twoD_source >> 16) & 0x01FFF;
+        unsigned int src_y = s->twoD_source & 0xFFFF;
         uint32_t src_base = s->twoD_source_base & 0x03FFFFFF;
-        uint8_t *src = s->local_mem + src_base;
-        int src_pitch = s->twoD_pitch & 0x1FFF;
-
-#define COPY_AREA(_bpp, _pixel_type, rtl) {                                   \
-        int y, x, index_d, index_s;                                           \
-        for (y = 0; y < height; y++) {                              \
-            for (x = 0; x < width; x++) {                           \
-                _pixel_type val;                                              \
-                                                                              \
-                if (rtl) {                                                    \
-                    index_s = ((src_y - y) * src_pitch + src_x - x) * _bpp;   \
-                    index_d = ((dst_y - y) * dst_pitch + dst_x - x) * _bpp;   \
-                } else {                                                      \
-                    index_s = ((src_y + y) * src_pitch + src_x + x) * _bpp;   \
-                    index_d = ((dst_y + y) * dst_pitch + dst_x + x) * _bpp;   \
-                }                                                             \
-                if (rop_mode == 1 && rop == 5) {                              \
-                    /* Invert dest */                                         \
-                    val = ~*(_pixel_type *)&dst[index_d];                     \
-                } else {                                                      \
-                    val = *(_pixel_type *)&src[index_s];                      \
-                }                                                             \
-                *(_pixel_type *)&dst[index_d] = val;                          \
-            }                                                                 \
-        }                                                                     \
-    }
-        switch (format) {
-        case 0:
-            COPY_AREA(1, uint8_t, rtl);
-            break;
-        case 1:
-            COPY_AREA(2, uint16_t, rtl);
-            break;
-        case 2:
-            COPY_AREA(4, uint32_t, rtl);
-            break;
+        unsigned int src_pitch = s->twoD_pitch & 0x1FFF;
+
+        if (!src_pitch) {
+            qemu_log_mask(LOG_GUEST_ERROR, "sm501: Zero src pitch.\n");
+            return;
+        }
+
+        if (rtl) {
+            src_x -= width - 1;
+            src_y -= height - 1;
+        }
+
+        if (src_base >= get_local_mem_size(s) || src_base +
+            (src_x + width + (src_y + height) * (src_pitch + width)) *
+            (1 << format) >= get_local_mem_size(s)) {
+            qemu_log_mask(LOG_GUEST_ERROR,
+                          "sm501: 2D op src is outside vram.\n");
+            return;
+        }
+
+        if ((rop_mode && rop == 0x5) || (!rop_mode && rop == 0x55)) {
+            /* Invert dest, is there a way to do this with pixman? */
+            unsigned int x, y, i;
+            uint8_t *d = s->local_mem + dst_base;
+
+            for (y = 0; y < height; y++) {
+                i = (dst_x + (dst_y + y) * dst_pitch) * (1 << format);
+                for (x = 0; x < width; x++, i += (1 << format)) {
+                    switch (format) {
+                    case 0:
+                        d[i] = ~d[i];
+                        break;
+                    case 1:
+                        *(uint16_t *)&d[i] = ~*(uint16_t *)&d[i];
+                        break;
+                    case 2:
+                        *(uint32_t *)&d[i] = ~*(uint32_t *)&d[i];
+                        break;
+                    }
+                }
+            }
+        } else {
+            /* Do copy src for unimplemented ops, better than unpainted area */
+            if ((rop_mode && (rop != 0xc || rop2_source_is_pattern)) ||
+                (!rop_mode && rop != 0xcc)) {
+                qemu_log_mask(LOG_UNIMP,
+                              "sm501: rop%d op %x%s not implemented\n",
+                              (rop_mode ? 2 : 3), rop,
+                              (rop2_source_is_pattern ?
+                                  " with pattern source" : ""));
+            }
+            /* Check for overlaps, this could be made more exact */
+            uint32_t sb, se, db, de;
+            sb = src_base + src_x + src_y * (width + src_pitch);
+            se = sb + width + height * (width + src_pitch);
+            db = dst_base + dst_x + dst_y * (width + dst_pitch);
+            de = db + width + height * (width + dst_pitch);
+            if (rtl && ((db >= sb && db <= se) || (de >= sb && de <= se))) {
+                /* regions may overlap: copy via temporary */
+                int llb = width * (1 << format);
+                int tmp_stride = DIV_ROUND_UP(llb, sizeof(uint32_t));
+                uint32_t *tmp = g_malloc(tmp_stride * sizeof(uint32_t) *
+                                         height);
+                pixman_blt((uint32_t *)&s->local_mem[src_base], tmp,
+                           src_pitch * (1 << format) / sizeof(uint32_t),
+                           tmp_stride, 8 * (1 << format), 8 * (1 << format),
+                           src_x, src_y, 0, 0, width, height);
+                pixman_blt(tmp, (uint32_t *)&s->local_mem[dst_base],
+                           tmp_stride,
+                           dst_pitch * (1 << format) / sizeof(uint32_t),
+                           8 * (1 << format), 8 * (1 << format),
+                           0, 0, dst_x, dst_y, width, height);
+                g_free(tmp);
+            } else {
+                pixman_blt((uint32_t *)&s->local_mem[src_base],
+                           (uint32_t *)&s->local_mem[dst_base],
+                           src_pitch * (1 << format) / sizeof(uint32_t),
+                           dst_pitch * (1 << format) / sizeof(uint32_t),
+                           8 * (1 << format), 8 * (1 << format),
+                           src_x, src_y, dst_x, dst_y, width, height);
+            }
         }
         break;
     }
-    case 0x01: /* fill rectangle */
+    case 1: /* Rectangle Fill */
     {
         uint32_t color = s->twoD_foreground;
 
-#define FILL_RECT(_bpp, _pixel_type) {                                      \
-        int y, x;                                                           \
-        for (y = 0; y < height; y++) {                            \
-            for (x = 0; x < width; x++) {                         \
-                int index = ((dst_y + y) * dst_pitch + dst_x + x) * _bpp;   \
-                *(_pixel_type *)&dst[index] = (_pixel_type)color;           \
-            }                                                               \
-        }                                                                   \
-    }
-
-        switch (format) {
-        case 0:
-            FILL_RECT(1, uint8_t);
-            break;
-        case 1:
-            color = cpu_to_le16(color);
-            FILL_RECT(2, uint16_t);
-            break;
-        case 2:
+        if (format == 2) {
             color = cpu_to_le32(color);
-            FILL_RECT(4, uint32_t);
-            break;
+        } else if (format == 1) {
+            color = cpu_to_le16(color);
         }
+
+        pixman_fill((uint32_t *)&s->local_mem[dst_base],
+                    dst_pitch * (1 << format) / sizeof(uint32_t),
+                    8 * (1 << format), dst_x, dst_y, width, height, color);
         break;
     }
     default:
-- 
2.23.0

