linux/arch/x86/include/asm/switch_to.h

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _ASM_X86_SWITCH_TO_H
#define _ASM_X86_SWITCH_TO_H

#include <linux/sched/task_stack.h>

struct task_struct; /* one of the stranger aspects of C forward declarations */

struct task_struct *__switch_to_asm(struct task_struct *prev,
				    struct task_struct *next);

__visible struct task_struct *__switch_to(struct task_struct *prev,
					  struct task_struct *next);

asmlinkage void ret_from_fork_asm(void);
__visible void ret_from_fork(struct task_struct *prev, struct pt_regs *regs,
			     int (*fn)(void *), void *fn_arg);

/*
 * This is the structure pointed to by thread.sp for an inactive task.  The
 * order of the fields must match the code in __switch_to_asm().
 */
struct inactive_task_frame { … };

struct fork_frame { … };

#define switch_to(prev, next, last) …

#ifdef CONFIG_X86_32
static inline void refresh_sysenter_cs(struct thread_struct *thread)
{
	/* Only happens when SEP is enabled, no need to test "SEP"arately: */
	if (unlikely(this_cpu_read(cpu_tss_rw.x86_tss.ss1) == thread->sysenter_cs))
		return;

	this_cpu_write(cpu_tss_rw.x86_tss.ss1, thread->sysenter_cs);
	wrmsr(MSR_IA32_SYSENTER_CS, thread->sysenter_cs, 0);
}
#endif

/* This is used when switching tasks or entering/exiting vm86 mode. */
static inline void update_task_stack(struct task_struct *task)
{ … }

static inline void kthread_frame_init(struct inactive_task_frame *frame,
				      int (*fun)(void *), void *arg)
{ … }

#endif /* _ASM_X86_SWITCH_TO_H */