accel/tcg: Split out handle_sigsegv_accerr_write

This is the major portion of handle_cpu_signal which is specific
to tcg, handling the page protections for the translations.
Most of the rest will migrate to linux-user/ shortly.

Reviewed-by: Warner Losh <imp@bsdimp.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
v2: Pass guest address to handle_sigsegv_accerr_write.

include/exec/exec-all.h

@@ -673,6 +673,18 @@ static inline tb_page_addr_t get_page_addr_code_hostp(CPUArchState *env,
  */
 MMUAccessType adjust_signal_pc(uintptr_t *pc, bool is_write);
 
+/**
+ * handle_sigsegv_accerr_write:
+ * @cpu: the cpu context
+ * @old_set: the sigset_t from the signal ucontext_t
+ * @host_pc: the host pc, adjusted for the signal
+ * @host_addr: the host address of the fault
+ *
+ * Return true if the write fault has been handled, and should be re-tried.
+ */
+bool handle_sigsegv_accerr_write(CPUState *cpu, sigset_t *old_set,
+                                 uintptr_t host_pc, abi_ptr guest_addr);
+
 /**
  * cpu_signal_handler
  * @signum: host signal number