svn commit: r327819 - head/sys/amd64/amd64

[Konstantin Belousov]

Author: kib
Date: Thu Jan 11 12:54:33 2018
New Revision: 327819
URL: https://svnweb.freebsd.org/changeset/base/327819

Log:
  Do not clear %RFLAGS.DF on fast syscall entry.
  
  Hardware already did it for us due to the mask loaded into the
  MSR_SF_MASK msr register.
  
  Reviewed by:	jhb
  Sponsored by:	The FreeBSD Foundation
  MFC after:	1 week
  Differential revision:	https://reviews.freebsd.org/D13838

Modified:
  head/sys/amd64/amd64/exception.S

Modified: head/sys/amd64/amd64/exception.S
==============================================================================
--- head/sys/amd64/amd64/exception.S	Thu Jan 11 12:40:43 2018	(r327818)
+++ head/sys/amd64/amd64/exception.S	Thu Jan 11 12:54:33 2018	(r327819)
@@ -410,7 +410,6 @@ IDTVEC(fast_syscall)
 	movq	%r14,TF_R14(%rsp)	/* C preserved */
 	movq	%r15,TF_R15(%rsp)	/* C preserved */
 	movl	$TF_HASSEGS,TF_FLAGS(%rsp)
-	cld
 	FAKE_MCOUNT(TF_RIP(%rsp))
 	movq	PCPU(CURTHREAD),%rdi
 	movq	%rsp,TD_FRAME(%rdi)