drm: mm: fix range restricted allocations

With the code cleanup in

7a6b2896f261894dde287d3faefa4b432cddca53 is the first bad commit
commit 7a6b2896f261894dde287d3faefa4b432cddca53
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Fri Jul 2 15:02:15 2010 +0100

    drm_mm: extract check_free_mm_node

I've botched up the range-restriction checks. The result is usually
an X server dying with SIGBUS in libpixman (software fallback rendering).
Change the code to adjust the start and end for range restricted
allocations. IMHO this even makes the code a bit clearer.

Fixes regression bug: https://bugs.freedesktop.org/show_bug.cgi?id=29738

Reported-by-Tested-by: Till MAtthiesen <entropy@everymail.net>
Acked-by: Alex Deucher <alexdeucher@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Dave Airlie <airlied@redhat.com>

1 files changed, 14 insertions, 10 deletions

diff --git a/drivers/gpu/drm/drm_mm.c b/drivers/gpu/drm/drm_mm.c
index da99edc5088..a6bfc302ed9 100644
--- a/drivers/gpu/drm/drm_mm.c
+++ b/drivers/gpu/drm/drm_mm.c
@@ -285,21 +285,21 @@ void drm_mm_put_block(struct drm_mm_node *cur)
 
 EXPORT_SYMBOL(drm_mm_put_block);
 
-static int check_free_mm_node(struct drm_mm_node *entry, unsigned long size,
-                              unsigned alignment)
+static int check_free_hole(unsigned long start, unsigned long end,
+                           unsigned long size, unsigned alignment)
 {
         unsigned wasted = 0;
 
-        if (entry->size < size)
+        if (end - start < size)
                 return 0;
 
         if (alignment) {
-                register unsigned tmp = entry->start % alignment;
+                unsigned tmp = start % alignment;
                 if (tmp)
                         wasted = alignment - tmp;
         }
 
-        if (entry->size >= size + wasted) {
+        if (end >= start + size + wasted) {
                 return 1;
         }
 
@@ -320,7 +320,8 @@ struct drm_mm_node *drm_mm_search_free(const struct drm_mm *mm,
         best_size = ~0UL;
 
         list_for_each_entry(entry, &mm->free_stack, free_stack) {
-                if (!check_free_mm_node(entry, size, alignment))
+                if (!check_free_hole(entry->start, entry->start + entry->size,
+                                     size, alignment))
                         continue;
 
                 if (!best_match)
@@ -353,10 +354,12 @@ struct drm_mm_node *drm_mm_search_free_in_range(const struct drm_mm *mm,
         best_size = ~0UL;
 
         list_for_each_entry(entry, &mm->free_stack, free_stack) {
-                if (entry->start > end || (entry->start+entry->size) < start)
-                        continue;
+                unsigned long adj_start = entry->start < start ?
+                        start : entry->start;
+                unsigned long adj_end = entry->start + entry->size > end ?
+                        end : entry->start + entry->size;
 
-                if (!check_free_mm_node(entry, size, alignment))
+                if (!check_free_hole(adj_start, adj_end, size, alignment))
                         continue;
 
                 if (!best_match)
@@ -449,7 +452,8 @@ int drm_mm_scan_add_block(struct drm_mm_node *node)
         node->free_stack.prev = prev_free;
         node->free_stack.next = next_free;
 
-        if (check_free_mm_node(node, mm->scan_size, mm->scan_alignment)) {
+        if (check_free_hole(node->start, node->start + node->size,
+                            mm->scan_size, mm->scan_alignment)) {
                 mm->scan_hit_start = node->start;
                 mm->scan_hit_size = node->size;