/* 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 {
#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
        unsigned long bx;

        /*
         * These two fields must be together.  They form a stack frame header,
         * needed by get_frame_pointer().
         */
        unsigned long bp;
        unsigned long ret_addr;
};

struct fork_frame {
        struct inactive_task_frame frame;
        struct pt_regs regs;
};

#define switch_to(prev, next, last)                                     \
do {                                                                    \
        ((last) = __switch_to_asm((prev), (next)));                     \
} while (0)

#ifdef CONFIG_X86_32
#include <asm/msr.h>

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);
        wrmsrq(MSR_IA32_SYSENTER_CS, thread->sysenter_cs);
}
#endif

/* This is used when switching tasks or entering/exiting vm86 mode. */
static inline void update_task_stack(struct task_struct *task)
{
        /* sp0 always points to the entry trampoline stack, which is constant: */
#ifdef CONFIG_X86_32
        this_cpu_write(cpu_tss_rw.x86_tss.sp1, task->thread.sp0);
#else
        if (!cpu_feature_enabled(X86_FEATURE_FRED) && cpu_feature_enabled(X86_FEATURE_XENPV))
                /* Xen PV enters the kernel on the thread stack. */
                load_sp0(task_top_of_stack(task));
#endif
}

static inline void kthread_frame_init(struct inactive_task_frame *frame,
                                      int (*fun)(void *), void *arg)
{
        frame->bx = (unsigned long)fun;
#ifdef CONFIG_X86_32
        frame->di = (unsigned long)arg;
#else
        frame->r12 = (unsigned long)arg;
#endif
}

#endif /* _ASM_X86_SWITCH_TO_H */