tcg: Manage splitwx in tc_ptr_to_region_tree by hand

The use in tcg_tb_lookup is given a random pc that comes from the pc
of a signal handler.  Do not assert that the pointer is already within
the code gen buffer at all, much less the writable mirror of it.

Fixes: db0c51a
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

tcg/tcg.c

@@ -513,11 +513,21 @@ static void tcg_region_trees_init(void)
     }
 }
 
-static struct tcg_region_tree *tc_ptr_to_region_tree(const void *cp)
+static struct tcg_region_tree *tc_ptr_to_region_tree(const void *p)
 {
-    void *p = tcg_splitwx_to_rw(cp);
     size_t region_idx;
 
+    /*
+     * Like tcg_splitwx_to_rw, with no assert.  The pc may come from
+     * a signal handler over which the caller has no control.
+     */
+    if (!in_code_gen_buffer(p)) {
+        p -= tcg_splitwx_diff;
+        if (!in_code_gen_buffer(p)) {
+            return NULL;
+        }
+    }
+
     if (p < region.start_aligned) {
         region_idx = 0;
     } else {
@@ -536,6 +546,7 @@ void tcg_tb_insert(TranslationBlock *tb)
 {
     struct tcg_region_tree *rt = tc_ptr_to_region_tree(tb->tc.ptr);
 
+    g_assert(rt != NULL);
     qemu_mutex_lock(&rt->lock);
     g_tree_insert(rt->tree, &tb->tc, tb);
     qemu_mutex_unlock(&rt->lock);
@@ -545,6 +556,7 @@ void tcg_tb_remove(TranslationBlock *tb)
 {
     struct tcg_region_tree *rt = tc_ptr_to_region_tree(tb->tc.ptr);
 
+    g_assert(rt != NULL);
     qemu_mutex_lock(&rt->lock);
     g_tree_remove(rt->tree, &tb->tc);
     qemu_mutex_unlock(&rt->lock);
@@ -561,6 +573,10 @@ TranslationBlock *tcg_tb_lookup(uintptr_t tc_ptr)
     TranslationBlock *tb;
     struct tb_tc s = { .ptr = (void *)tc_ptr };
 
+    if (rt == NULL) {
+        return NULL;
+    }
+
     qemu_mutex_lock(&rt->lock);
     tb = g_tree_lookup(rt->tree, &s);
     qemu_mutex_unlock(&rt->lock);