gdbstub: split out softmmu/user specifics for syscall handling

Most of the syscall code is config agnostic aside from the size of
target_ulong. In preparation for the next patch move the final bits
of specialisation into the appropriate user and softmmu helpers.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20230302190846.2593720-26-alex.bennee@linaro.org>
Message-Id: <20230303025805.625589-26-richard.henderson@linaro.org>

gdbstub/internals.h

@@ -195,6 +195,9 @@ bool gdb_handled_syscall(void);
 void gdb_disable_syscalls(void);
 void gdb_syscall_reset(void);
 
+/* user/softmmu specific syscall handling */
+void gdb_syscall_handling(const char *syscall_packet);
+
 /*
  * Break/Watch point support - there is an implementation for softmmu
  * and user mode.

gdbstub/softmmu.c

@@ -103,6 +103,20 @@ static void gdb_chr_event(void *opaque, QEMUChrEvent event)
     }
 }
 
+/*
+ * In softmmu mode we stop the VM and wait to send the syscall packet
+ * until notification that the CPU has stopped. This must be done
+ * because if the packet is sent now the reply from the syscall
+ * request could be received while the CPU is still in the running
+ * state, which can cause packets to be dropped and state transition
+ * 'T' packets to be sent while the syscall is still being processed.
+ */
+void gdb_syscall_handling(const char *syscall_packet)
+{
+    vm_stop(RUN_STATE_DEBUG);
+    qemu_cpu_kick(gdbserver_state.c_cpu);
+}
+
 static void gdb_vm_state_change(void *opaque, bool running, RunState state)
 {
     CPUState *cpu = gdbserver_state.c_cpu;

gdbstub/syscalls.c

@@ -105,9 +105,7 @@ void gdb_do_syscallv(gdb_syscall_complete_cb cb, const char *fmt, va_list va)
     }
 
     gdbserver_syscall_state.current_syscall_cb = cb;
-#ifndef CONFIG_USER_ONLY
+
-    vm_stop(RUN_STATE_DEBUG);
-#endif
     p = &gdbserver_syscall_state.syscall_buf[0];
     p_end = &gdbserver_syscall_state.syscall_buf[sizeof(gdbserver_syscall_state.syscall_buf)];
     *(p++) = 'F';
@@ -142,27 +140,8 @@ void gdb_do_syscallv(gdb_syscall_complete_cb cb, const char *fmt, va_list va)
         }
     }
     *p = 0;
-#ifdef CONFIG_USER_ONLY
+
-    gdb_put_packet(gdbserver_syscall_state.syscall_buf);
+    gdb_syscall_handling(gdbserver_syscall_state.syscall_buf);
-    /*
-     * Return control to gdb for it to process the syscall request.
-     * Since the protocol requires that gdb hands control back to us
-     * using a "here are the results" F packet, we don't need to check
-     * gdb_handlesig's return value (which is the signal to deliver if
-     * execution was resumed via a continue packet).
-     */
-    gdb_handlesig(gdbserver_state.c_cpu, 0);
-#else
-    /*
-     * In this case wait to send the syscall packet until notification that
-     * the CPU has stopped.  This must be done because if the packet is sent
-     * now the reply from the syscall request could be received while the CPU
-     * is still in the running state, which can cause packets to be dropped
-     * and state transition 'T' packets to be sent while the syscall is still
-     * being processed.
-     */
-    qemu_cpu_kick(gdbserver_state.c_cpu);
-#endif
 }
 
 void gdb_do_syscall(gdb_syscall_complete_cb cb, const char *fmt, ...)

gdbstub/user.c

@@ -472,3 +472,17 @@ void gdb_breakpoint_remove_all(CPUState *cs)
 {
     cpu_breakpoint_remove_all(cs, BP_GDB);
 }
+
+/*
+ * For user-mode syscall support we send the system call immediately
+ * and then return control to gdb for it to process the syscall request.
+ * Since the protocol requires that gdb hands control back to us
+ * using a "here are the results" F packet, we don't need to check
+ * gdb_handlesig's return value (which is the signal to deliver if
+ * execution was resumed via a continue packet).
+ */
+void gdb_syscall_handling(const char *syscall_packet)
+{
+    gdb_put_packet(syscall_packet);
+    gdb_handlesig(gdbserver_state.c_cpu, 0);
+}