Commit 64604d54 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

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: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 2f0f9e9a

arch/x86/entry/entry_64.S

+0 −2
Original line number Diff line number Diff line
@@ -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

arch/x86/include/asm/switch_to.h

+1 −1
Original line number Diff line number Diff line
@@ -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

arch/x86/kernel/process_64.c

+0 −7
Original line number Diff line number Diff line
@@ -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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