/* 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;
#if !defined(CONFIG_PAX_KERNEXEC_PLUGIN_METHOD_OR) && !defined(CONFIG_PAX_RAP_XOR)
    unsigned long r12;
#endif
#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;
#ifdef CONFIG_X86_32
    struct pt_regs regs;
#endif
};

#ifdef CONFIG_X86_32
#define switch_to(prev, next, last)                    \
do {                                    \
    ((last) = __switch_to_asm((prev), (next)));            \
} while (0)
#else
#define switch_to(prev, next, last)                    \
do {                                    \
{                    \
unsigned long sp1, sp2;            \
asm("mov %%rsp,%0" : "=g" (sp1));    \
sp1 &= ~(THREAD_SIZE-1);        \
sp2 = (unsigned long)prev->stack;    \
sp2 &= ~(THREAD_SIZE-1);        \
BUG_ON(sp1 != sp2);            \
                    \
sp1 = next->thread.sp;            \
sp1 &= ~(THREAD_SIZE-1);        \
sp2 = (unsigned long)next->stack;    \
sp2 &= ~(THREAD_SIZE-1);        \
BUG_ON(sp1 != sp2);            \
}                    \
    ((last) = __switch_to_asm((prev), (next)));            \
} while (0)
#endif

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

    tss->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 __always_inline void update_task_stack(struct tss_struct *tss, struct task_struct *task)
{
    /* sp0 always points to the entry trampoline stack, which is constant: */
#ifdef CONFIG_X86_32
    tss->x86_tss.sp1 = task->thread.sp0;
#else
    /* Xen PV enters the kernel on the thread stack. */
    if (cpu_feature_enabled(X86_FEATURE_XENPV))
        load_sp0(tss, 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->r13 = (unsigned long)arg;
#endif
}

#endif /* _ASM_X86_SWITCH_TO_H */