From 092c74e420952c7cb68141731f2b562245b51eeb Mon Sep 17 00:00:00 2001 From: Brian Gerst Date: Wed, 4 May 2016 22:44:36 -0400 Subject: x86/entry, sched/x86: Don't save/restore EFLAGS on task switch Now that NT is filtered by the SYSENTER entry code, it is safe to skip saving and restoring flags on task switch. Also remove a leftover reset of flags on 64-bit fork. Signed-off-by: Brian Gerst Acked-by: Andy Lutomirski Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Borislav Petkov Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1462416278-11974-2-git-send-email-brgerst@gmail.com Signed-off-by: Ingo Molnar --- arch/x86/entry/entry_32.S | 4 ---- arch/x86/entry/entry_64.S | 3 --- 2 files changed, 7 deletions(-) (limited to 'arch/x86/entry') diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S index 10868aa734dc..c84d99bfff94 100644 --- a/arch/x86/entry/entry_32.S +++ b/arch/x86/entry/entry_32.S @@ -209,8 +209,6 @@ ENTRY(ret_from_fork) call schedule_tail GET_THREAD_INFO(%ebp) popl %eax - pushl $0x0202 # Reset kernel eflags - popfl /* When we fork, we trace the syscall return in the child, too. */ movl %esp, %eax @@ -223,8 +221,6 @@ ENTRY(ret_from_kernel_thread) call schedule_tail GET_THREAD_INFO(%ebp) popl %eax - pushl $0x0202 # Reset kernel eflags - popfl movl PT_EBP(%esp), %eax call *PT_EBX(%esp) movl $0, PT_EAX(%esp) diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index 6344629ae1ce..9ee0da1807ed 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -372,9 +372,6 @@ END(ptregs_\func) ENTRY(ret_from_fork) LOCK ; btr $TIF_FORK, TI_flags(%r8) - pushq $0x0002 - popfq /* reset kernel eflags */ - call schedule_tail /* rdi: 'prev' task parameter */ testb $3, CS(%rsp) /* from kernel_thread? */ -- cgit v1.2.3