Unify the checking for lock misbehavior in the various syscall()

implementations and adjust some of the checks while I'm here:
- Add a new check to make sure we don't return from a syscall in a critical
  section.
- Add a new explicit check before userret() to make sure we don't return
  with any locks held.  The advantage here is that we can include the
  syscall number and name in syscall() whereas that info is not available
  in userret().
- Drop the mtx_assert()'s of sched_lock and Giant.  They are replaced by
  the more general checks just added.

MFC after:	2 weeks

1 files changed, 13 insertions, 5 deletions

diff --git a/sys/amd64/ia32/ia32_syscall.c b/sys/amd64/ia32/ia32_syscall.c
index 5b3086a9d4f5..644235dc3bf9 100644
--- a/sys/amd64/ia32/ia32_syscall.c
+++ b/sys/amd64/ia32/ia32_syscall.c
@@ -244,6 +244,19 @@ ia32_syscall(struct trapframe frame)
 	}
 
 	/*
+	 * Check for misbehavior.
+	 */
+	WITNESS_WARN(WARN_PANIC, NULL, "System call %s returning",
+	    (code >= 0 && code < SYS_MAXSYSCALL) ? freebsd32_syscallnames[code] : "???");
+	KASSERT(td->td_critnest == 0,
+	    ("System call %s returning in a critical section",
+	    (code >= 0 && code < SYS_MAXSYSCALL) ? freebsd32_syscallnames[code] : "???"));
+	KASSERT(td->td_locks == 0,
+	    ("System call %s returning with %d locks held",
+	    (code >= 0 && code < SYS_MAXSYSCALL) ? freebsd32_syscallnames[code] : "???",
+	    td->td_locks));
+
+	/*
 	 * Handle reschedule and other end-of-syscall issues
 	 */
 	userret(td, &frame);
@@ -263,11 +276,6 @@ ia32_syscall(struct trapframe frame)
 	STOPEVENT(p, S_SCX, code);
  
 	PTRACESTOP_SC(p, td, S_PT_SCX);
-
-	WITNESS_WARN(WARN_PANIC, NULL, "System call %s returning",
-	    (code >= 0 && code < SYS_MAXSYSCALL) ? freebsd32_syscallnames[code] : "???");
-	mtx_assert(&sched_lock, MA_NOTOWNED);
-	mtx_assert(&Giant, MA_NOTOWNED);
 }