target-sh4: implement writes to mmaped ITLB

Some Linux kernels seems to implement ITLB/UTLB flushing through by
writing all TLB entries through the memory mapped interface instead
of writing one to MMUCR.TI.

Implement memory mapped ITLB write interface so that such kernels can
boot. This fixes https://bugs.launchpad.net/bugs/700774 .

Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
diff --git a/target-sh4/helper.c b/target-sh4/helper.c
index 9e70352..863886b 100644
--- a/target-sh4/helper.c
+++ b/target-sh4/helper.c
@@ -544,6 +544,25 @@
     tlb_flush(s, 1);
 }
 
+void cpu_sh4_write_mmaped_itlb_addr(CPUSH4State *s, target_phys_addr_t addr,
+				    uint32_t mem_value)
+{
+    uint32_t vpn = (mem_value & 0xfffffc00) >> 10;
+    uint8_t v = (uint8_t)((mem_value & 0x00000100) >> 8);
+    uint8_t asid = (uint8_t)(mem_value & 0x000000ff);
+
+    int index = (addr & 0x00003f00) >> 8;
+    tlb_t * entry = &s->itlb[index];
+    if (entry->v) {
+        /* Overwriting valid entry in itlb. */
+        target_ulong address = entry->vpn << 10;
+        tlb_flush_page(s, address);
+    }
+    entry->asid = asid;
+    entry->vpn = vpn;
+    entry->v = v;
+}
+
 void cpu_sh4_write_mmaped_utlb_addr(CPUSH4State *s, target_phys_addr_t addr,
 				    uint32_t mem_value)
 {