hw/core: Add TCGCPUOps.record_sigsegv

Add a new user-only interface for updating cpu state before
raising a signal.  This will replace tlb_fill for user-only
and should result in less boilerplate for each guest.

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

include/hw/core/tcg-cpu-ops.h

@@ -111,6 +111,32 @@ struct TCGCPUOps {
      */
     bool (*io_recompile_replay_branch)(CPUState *cpu,
                                        const TranslationBlock *tb);
+#else
+    /**
+     * record_sigsegv:
+     * @cpu: cpu context
+     * @addr: faulting guest address
+     * @access_type: access was read/write/execute
+     * @maperr: true for invalid page, false for permission fault
+     * @ra: host pc for unwinding
+     *
+     * We are about to raise SIGSEGV with si_code set for @maperr,
+     * and si_addr set for @addr.  Record anything further needed
+     * for the signal ucontext_t.
+     *
+     * If the emulated kernel does not provide anything to the signal
+     * handler with anything besides the user context registers, and
+     * the siginfo_t, then this hook need do nothing and may be omitted.
+     * Otherwise, record the data and return; the caller will raise
+     * the signal, unwind the cpu state, and return to the main loop.
+     *
+     * If it is simpler to re-use the sysemu tlb_fill code, @ra is provided
+     * so that a "normal" cpu exception can be raised.  In this case,
+     * the signal must be raised by the architecture cpu_loop.
+     */
+    void (*record_sigsegv)(CPUState *cpu, vaddr addr,
+                           MMUAccessType access_type,
+                           bool maperr, uintptr_t ra);
 #endif /* CONFIG_SOFTMMU */
 #endif /* NEED_CPU_H */