trace: [*-user] Add events to trace guest syscalls in syscall emulation mode

Adds two events to trace syscalls in syscall emulation mode (*-user):

* guest_user_syscall: Emitted before the syscall is emulated; contains
  the syscall number and arguments.

* guest_user_syscall_ret: Emitted after the syscall is emulated;
  contains the syscall number and return value.

Signed-off-by: Lluís Vilanova <vilanova@ac.upc.edu>
Message-id: 146651712411.12388.10024905980452504938.stgit@fimbulvetr.bsc.es
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
diff --git a/trace-events b/trace-events
index 9d76de8..4767059 100644
--- a/trace-events
+++ b/trace-events
@@ -156,3 +156,19 @@
 #
 # Targets: TCG(all)
 disable vcpu tcg guest_mem_before(TCGv vaddr, uint8_t info) "info=%d", "vaddr=0x%016"PRIx64" info=%d"
+
+# @num: System call number.
+# @arg*: System call argument value.
+#
+# Start executing a guest system call in syscall emulation mode.
+#
+# Targets: TCG(all)
+disable vcpu guest_user_syscall(uint64_t num, uint64_t arg1, uint64_t arg2, uint64_t arg3, uint64_t arg4, uint64_t arg5, uint64_t arg6, uint64_t arg7, uint64_t arg8) "num=0x%016"PRIx64" arg1=0x%016"PRIx64" arg2=0x%016"PRIx64" arg3=0x%016"PRIx64" arg4=0x%016"PRIx64" arg5=0x%016"PRIx64" arg6=0x%016"PRIx64" arg7=0x%016"PRIx64" arg8=0x%016"PRIx64
+
+# @num: System call number.
+# @ret: System call result value.
+#
+# Finish executing a guest system call in syscall emulation mode.
+#
+# Targets: TCG(all)
+disable vcpu guest_user_syscall_ret(uint64_t num, uint64_t ret) "num=0x%016"PRIx64" ret=0x%016"PRIx64