svn commit: r366336 - head/sys/kern

[Edward Tomasz Napierala]

Author: trasz
Date: Thu Oct  1 18:45:31 2020
New Revision: 366336
URL: https://svnweb.freebsd.org/changeset/base/366336

Log:
  Only clear TDP_NERRNO when needed, ie when it's previously been set.
  
  Reviewed by:	kib
  Tested by:	pho
  Sponsored by:	DARPA
  Differential Revision:	https://reviews.freebsd.org/D26612

Modified:
  head/sys/kern/subr_syscall.c

Modified: head/sys/kern/subr_syscall.c
==============================================================================
--- head/sys/kern/subr_syscall.c	Thu Oct  1 18:17:56 2020	(r366335)
+++ head/sys/kern/subr_syscall.c	Thu Oct  1 18:45:31 2020	(r366336)
@@ -138,7 +138,8 @@ syscallenter(struct thread *td)
 		(void)sigfastblock_fetch(td);
 
 	/* Let system calls set td_errno directly. */
-	td->td_pflags &= ~TDP_NERRNO;
+	KASSERT((td->td_pflags & TDP_NERRNO) == 0,
+	    ("%s: TDP_NERRNO set", __func__));
 
 	if (__predict_false(SYSTRACE_ENABLED() ||
 	    AUDIT_SYSCALL_ENTER(sa->code, td))) {
@@ -149,7 +150,9 @@ syscallenter(struct thread *td)
 #endif
 		error = (sa->callp->sy_call)(td, sa->args);
 		/* Save the latest error return value. */
-		if (__predict_false((td->td_pflags & TDP_NERRNO) == 0))
+		if (__predict_false((td->td_pflags & TDP_NERRNO) != 0))
+			td->td_pflags &= ~TDP_NERRNO;
+		else
 			td->td_errno = error;
 		AUDIT_SYSCALL_EXIT(error, td);
 #ifdef KDTRACE_HOOKS
@@ -161,7 +164,9 @@ syscallenter(struct thread *td)
 	} else {
 		error = (sa->callp->sy_call)(td, sa->args);
 		/* Save the latest error return value. */
-		if (__predict_false((td->td_pflags & TDP_NERRNO) == 0))
+		if (__predict_false((td->td_pflags & TDP_NERRNO) != 0))
+			td->td_pflags &= ~TDP_NERRNO;
+		else
 			td->td_errno = error;
 	}
 	syscall_thread_exit(td, sa->callp);