diff --git a/cpu-exec.c b/cpu-exec.c
index 372aeac..0f84857 100644
--- a/cpu-exec.c
+++ b/cpu-exec.c
@@ -1197,15 +1197,39 @@
 {
     struct siginfo *info = pinfo;
     struct ucontext *uc = puc;
-    unsigned long pc;
-    int is_write;
+    unsigned long pc = uc->uc_mcontext.sc_iaoq[0];
+    uint32_t insn = *(uint32_t *)pc;
+    int is_write = 0;
 
-    pc = uc->uc_mcontext.sc_iaoq[0];
-    /* FIXME: compute is_write */
-    is_write = 0;
+    /* XXX: need kernel patch to get write flag faster.  */
+    switch (insn >> 26) {
+    case 0x1a: /* STW */
+    case 0x19: /* STH */
+    case 0x18: /* STB */
+    case 0x1b: /* STWM */
+        is_write = 1;
+        break;
+
+    case 0x09: /* CSTWX, FSTWX, FSTWS */
+    case 0x0b: /* CSTDX, FSTDX, FSTDS */
+        /* Distinguish from coprocessor load ... */
+        is_write = (insn >> 9) & 1;
+        break;
+
+    case 0x03:
+        switch ((insn >> 6) & 15) {
+        case 0xa: /* STWS */
+        case 0x9: /* STHS */
+        case 0x8: /* STBS */
+        case 0xe: /* STWAS */
+        case 0xc: /* STBYS */
+            is_write = 1;
+        }
+        break;
+    }
+
     return handle_cpu_signal(pc, (unsigned long)info->si_addr, 
-                             is_write,
-                             &uc->uc_sigmask, puc);
+                             is_write, &uc->uc_sigmask, puc);
 }
 
 #else