Commit-ID: 64604d54d3115fee89598bfb6d8d2252f8a2d114
Gitweb: https://git.kernel.org/tip/64604d54d3115fee89598bfb6d8d2252f8a2d114
Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate: Tue, 19 Mar 2019 11:35:46 +0100
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Wed, 3 Apr 2019 11:02:24 +0200
sched/x86_64: Don't save flags on context switch
Now that we have objtool validating AC=1 state for all x86_64 code,
we can once again guarantee clean flags on schedule.
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
arch/x86/entry/entry_64.S | 2 --
arch/x86/include/asm/switch_to.h | 2 +-
arch/x86/kernel/process_64.c | 7 -------
3 files changed, 1 insertion(+), 10 deletions(-)
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 4fe27b67d7e2..1f0efdb7b629 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -291,7 +291,6 @@ ENTRY(__switch_to_asm)
pushq %r13
pushq %r14
pushq %r15
- pushfq
/* switch stack */
movq %rsp, TASK_threadsp(%rdi)
@@ -314,7 +313,6 @@ ENTRY(__switch_to_asm)
#endif
/* restore callee-saved registers */
- popfq
popq %r15
popq %r14
popq %r13
diff --git a/arch/x86/include/asm/switch_to.h b/arch/x86/include/asm/switch_to.h
index 157149d4129c..18a4b6890fa8 100644
--- a/arch/x86/include/asm/switch_to.h
+++ b/arch/x86/include/asm/switch_to.h
@@ -40,13 +40,13 @@ asmlinkage void ret_from_fork(void);
* order of the fields must match the code in __switch_to_asm().
*/
struct inactive_task_frame {
- unsigned long flags;
#ifdef CONFIG_X86_64
unsigned long r15;
unsigned long r14;
unsigned long r13;
unsigned long r12;
#else
+ unsigned long flags;
unsigned long si;
unsigned long di;
#endif
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 026a43be9bd1..844a28b29967 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -393,13 +393,6 @@ int copy_thread_tls(unsigned long clone_flags, unsigned long sp,
fork_frame = container_of(childregs, struct fork_frame, regs);
frame = &fork_frame->frame;
- /*
- * For a new task use the RESET flags value since there is no before.
- * All the status flags are zero; DF and all the system flags must also
- * be 0, specifically IF must be 0 because we context switch to the new
- * task with interrupts disabled.
- */
- frame->flags = X86_EFLAGS_FIXED;
frame->bp = 0;
frame->ret_addr = (unsigned long) ret_from_fork;
p->thread.sp = (unsigned long) fork_frame;
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