From 64604d54d3115fee89598bfb6d8d2252f8a2d114 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Tue, 19 Mar 2019 11:35:46 +0100 Subject: 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) Cc: Borislav Petkov Cc: Josh Poimboeuf Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Signed-off-by: Ingo Molnar --- 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; -- cgit v1.2.3-59-g8ed1b