[PATCH v3 24/24] gdbstub: split out softmmu/user specifics for syscall handling

["Alex Bennée" <alex.bennee@linaro.org>]

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>
---
 gdbstub/internals.h |  5 +++++
 gdbstub/softmmu.c   | 24 ++++++++++++++++++++++++
 gdbstub/syscalls.c  | 32 +++++++++++---------------------
 gdbstub/user.c      | 24 ++++++++++++++++++++++++
 4 files changed, 64 insertions(+), 21 deletions(-)

diff --git a/gdbstub/internals.h b/gdbstub/internals.h
index fe82facaeb..dce7c4f66f 100644
--- a/gdbstub/internals.h
+++ b/gdbstub/internals.h
@@ -193,6 +193,11 @@ bool gdb_handled_syscall(void);
 void gdb_disable_syscalls(void);
 void gdb_syscall_reset(void);
 
+/* user/softmmu specific signal handling */
+void gdb_pre_syscall_handling(void);
+bool gdb_send_syscall_now(void);
+void gdb_post_syscall_handling(void);
+
 /*
  * Break/Watch point support - there is an implementation for softmmu
  * and user mode.
diff --git a/gdbstub/softmmu.c b/gdbstub/softmmu.c
index b7e3829ca0..8f3c8ef449 100644
--- a/gdbstub/softmmu.c
+++ b/gdbstub/softmmu.c
@@ -101,6 +101,30 @@ 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_pre_syscall_handling(void)
+{
+    vm_stop(RUN_STATE_DEBUG);
+}
+
+bool gdb_send_syscall_now(void)
+{
+    return false;
+}
+
+void gdb_post_syscall_handling(void)
+{
+    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;
diff --git a/gdbstub/syscalls.c b/gdbstub/syscalls.c
index 1b63a1d197..24eee38136 100644
--- a/gdbstub/syscalls.c
+++ b/gdbstub/syscalls.c
@@ -102,9 +102,10 @@ 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
+
+    /* user/softmmu specific handling */
+    gdb_pre_syscall_handling();
+
     p = &gdbserver_syscall_state.syscall_buf[0];
     p_end = &gdbserver_syscall_state.syscall_buf[sizeof(gdbserver_syscall_state.syscall_buf)];
     *(p++) = 'F';
@@ -138,24 +139,13 @@ 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);
-    /* 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
+
+    if (gdb_send_syscall_now()) { /* true only for *-user */
+        gdb_put_packet(gdbserver_syscall_state.syscall_buf);
+    }
+
+    /* user/softmmu specific handling */
+    gdb_post_syscall_handling();
 }
 
 void gdb_do_syscall(gdb_syscall_complete_cb cb, const char *fmt, ...)
diff --git a/gdbstub/user.c b/gdbstub/user.c
index cc7eeb9afb..a5227e23cf 100644
--- a/gdbstub/user.c
+++ b/gdbstub/user.c
@@ -467,3 +467,27 @@ 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_pre_syscall_handling(void)
+{
+    return;
+}
+
+bool gdb_send_syscall_now(void)
+{
+    return true;
+}
+
+void gdb_post_syscall_handling(void)
+{
+    gdb_handlesig(gdbserver_state.c_cpu, 0);
+}
-- 
2.39.1