bsd-user/signal.c: implement abstract target / host signal translation

Implement host_to_target_signal and target_to_host_signal.

Signed-off-by: Stacey Son <sson@FreeBSD.org>
Signed-off-by: Kyle Evans <kevans@freebsd.org>
Signed-off-by: Warner Losh <imp@bsdimp.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

bsd-user/signal-common.h

@@ -13,8 +13,10 @@ long do_rt_sigreturn(CPUArchState *env);
 abi_long do_sigaltstack(abi_ulong uss_addr, abi_ulong uoss_addr, abi_ulong sp);
 long do_sigreturn(CPUArchState *env);
 void force_sig_fault(int sig, int code, abi_ulong addr);
+int host_to_target_signal(int sig);
 void process_pending_signals(CPUArchState *env);
 void queue_signal(CPUArchState *env, int sig, target_siginfo_t *info);
 void signal_init(void);
+int target_to_host_signal(int sig);
 
 #endif

bsd-user/signal.c

@@ -2,6 +2,7 @@
  *  Emulation of BSD signals
  *
  *  Copyright (c) 2003 - 2008 Fabrice Bellard
+ *  Copyright (c) 2013 Stacey Son
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
@@ -27,6 +28,21 @@
  * fork.
  */
 
+/*
+ * The BSD ABIs use the same singal numbers across all the CPU architectures, so
+ * (unlike Linux) these functions are just the identity mapping. This might not
+ * be true for XyzBSD running on AbcBSD, which doesn't currently work.
+ */
+int host_to_target_signal(int sig)
+{
+    return sig;
+}
+
+int target_to_host_signal(int sig)
+{
+    return sig;
+}
+
 /*
  * Queue a signal so that it will be send to the virtual CPU as soon as
  * possible.