linux-user: Fix broken m68k signal handling on 64 bit hosts

The m68k signal frame setup code which writes the signal return
trampoline code to the stack was assuming that a 'long' was 32 bits;
on 64 bit systems this meant we would end up writing the 32 bit
(2 insn) trampoline sequence to retaddr+4,retaddr+6 instead of
the intended retaddr+0,retaddr+2, resulting in a guest crash when
it tried to execute the invalid zero-bytes at retaddr+0.
Fix by using uint32_t instead; also use uint16_t rather than short
for consistency. This fixes bug LP:1404690.

Reported-by: Michel Boaventura
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
(cherry picked from commit 1669add752d9f29283f8ebf6a863d7b1e2d0f146)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

linux-user/signal.c

@@ -5091,7 +5091,7 @@ static void setup_frame(int sig, struct target_sigaction *ka,
     /* moveq #,d0; trap #0 */
 
     __put_user(0x70004e40 + (TARGET_NR_sigreturn << 16),
-                      (long *)(frame->retcode));
+                      (uint32_t *)(frame->retcode));
 
     /* Set up to return from userspace */
 
@@ -5225,8 +5225,8 @@ static void setup_rt_frame(int sig, struct target_sigaction *ka,
     /* moveq #,d0; notb d0; trap #0 */
 
     __put_user(0x70004600 + ((TARGET_NR_rt_sigreturn ^ 0xff) << 16),
-               (long *)(frame->retcode + 0));
-    __put_user(0x4e40, (short *)(frame->retcode + 4));
+               (uint32_t *)(frame->retcode + 0));
+    __put_user(0x4e40, (uint16_t *)(frame->retcode + 4));
 
     if (err)
         goto give_sigsegv;