diff --git a/include/exec/cpu-all.h b/include/exec/cpu-all.h
index d23ced1d12..034773e319 100644
--- a/include/exec/cpu-all.h
+++ b/include/exec/cpu-all.h
@@ -243,10 +243,14 @@ extern intptr_t qemu_host_page_mask;
 #define PAGE_WRITE_ORG 0x0010
 /* Invalidate the TLB entry immediately, helpful for s390x
  * Low-Address-Protection. Used with PAGE_WRITE in tlb_set_page_with_attrs() */
-#define PAGE_WRITE_INV 0x0040
+#define PAGE_WRITE_INV 0x0020
+/* Page is mapped shared.  */
+#define PAGE_SHARED    0x0040
+/* For use with page_set_flags: page is being replaced; target_data cleared. */
+#define PAGE_RESET     0x0080
 #if defined(CONFIG_BSD) && defined(CONFIG_USER_ONLY)
 /* FIXME: Code that sets/uses this is broken and needs to go away.  */
-#define PAGE_RESERVED  0x0020
+#define PAGE_RESERVED  0x0100
 #endif
 /* Target-specific bits that will be used via page_get_flags().  */
 #define PAGE_TARGET_1  0x0080
@@ -261,6 +265,8 @@ int walk_memory_regions(void *, walk_memory_regions_fn);
 int page_get_flags(target_ulong address);
 void page_set_flags(target_ulong start, target_ulong end, int flags);
 int page_check_range(target_ulong start, target_ulong len, int flags);
+void *page_get_target_data(target_ulong address);
+void *page_alloc_target_data(target_ulong address, size_t size);
 #endif
 
 CPUArchState *cpu_copy(CPUArchState *env);
diff --git a/accel/tcg/translate-all.c b/accel/tcg/translate-all.c
index 66d4bc4341..dbf08b55e2 100644
--- a/accel/tcg/translate-all.c
+++ b/accel/tcg/translate-all.c
@@ -110,6 +110,7 @@ typedef struct PageDesc {
     unsigned int code_write_count;
 #else
     unsigned long flags;
+    void *target_data;
 #endif
 #ifndef CONFIG_USER_ONLY
     QemuSpin lock;
@@ -2513,6 +2514,7 @@ int page_get_flags(target_ulong address)
 void page_set_flags(target_ulong start, target_ulong end, int flags)
 {
     target_ulong addr, len;
+    bool reset_target_data;
 
     /* This function should never be called with addresses outside the
        guest address space.  If this assert fires, it probably indicates
@@ -2529,6 +2531,8 @@ void page_set_flags(target_ulong start, target_ulong end, int flags)
     if (flags & PAGE_WRITE) {
         flags |= PAGE_WRITE_ORG;
     }
+    reset_target_data = !(flags & PAGE_VALID) || (flags & PAGE_RESET);
+    flags &= ~PAGE_RESET;
 
     for (addr = start, len = end - start;
          len != 0;
@@ -2542,10 +2546,34 @@ void page_set_flags(target_ulong start, target_ulong end, int flags)
             p->first_tb) {
             tb_invalidate_phys_page(addr, 0);
         }
+        if (reset_target_data && p->target_data) {
+            g_free(p->target_data);
+            p->target_data = NULL;
+        }
         p->flags = flags;
     }
 }
 
+void *page_get_target_data(target_ulong address)
+{
+    PageDesc *p = page_find(address >> TARGET_PAGE_BITS);
+    return p ? p->target_data : NULL;
+}
+
+void *page_alloc_target_data(target_ulong address, size_t size)
+{
+    PageDesc *p = page_find(address >> TARGET_PAGE_BITS);
+    void *ret = NULL;
+
+    if (p) {
+        ret = p->target_data;
+        if (!ret && (p->flags & PAGE_VALID)) {
+            p->target_data = ret = g_malloc0(size);
+        }
+    }
+    return ret;
+}
+
 int page_check_range(target_ulong start, target_ulong len, int flags)
 {
     PageDesc *p;
diff --git a/linux-user/mmap.c b/linux-user/mmap.c
index c1bed290f6..75e0355ff7 100644
--- a/linux-user/mmap.c
+++ b/linux-user/mmap.c
@@ -626,6 +626,10 @@ abi_long target_mmap(abi_ulong start, abi_ulong len, int target_prot,
         }
     }
  the_end1:
+    if ((flags & MAP_TYPE) == MAP_SHARED) {
+        page_flags |= PAGE_SHARED;
+    }
+    page_flags |= PAGE_RESET;
     page_set_flags(start, start + len, page_flags);
  the_end:
 #ifdef DEBUG_MMAP
@@ -818,9 +822,11 @@ abi_long target_mremap(abi_ulong old_addr, abi_ulong old_size,
         new_addr = -1;
     } else {
         new_addr = h2g(host_addr);
+        /* FIXME: Move page flags (and target_data?) for each page.  */
         prot = page_get_flags(old_addr);
         page_set_flags(old_addr, old_addr + old_size, 0);
-        page_set_flags(new_addr, new_addr + new_size, prot | PAGE_VALID);
+        page_set_flags(new_addr, new_addr + new_size,
+                       prot | PAGE_VALID | PAGE_RESET);
     }
     tb_invalidate_phys_range(new_addr, new_addr + new_size);
     mmap_unlock();
diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index e2af3c1494..52f50eca4b 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -4061,8 +4061,8 @@ static inline abi_ulong do_shmat(CPUArchState *cpu_env,
     raddr=h2g((unsigned long)host_raddr);
 
     page_set_flags(raddr, raddr + shm_info.shm_segsz,
-                   PAGE_VALID | PAGE_READ |
-                   ((shmflg & SHM_RDONLY)? 0 : PAGE_WRITE));
+                   PAGE_VALID | PAGE_SHARED | PAGE_RESET | PAGE_READ |
+                   (shmflg & SHM_RDONLY ? 0 : PAGE_WRITE));
 
     for (i = 0; i < N_SHM_REGIONS; i++) {
         if (!shm_regions[i].in_use) {
