1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef _ASM_X86_SWITCH_TO_H
3#define _ASM_X86_SWITCH_TO_H
4
5#include <linux/sched/task_stack.h>
6
7struct task_struct; /* one of the stranger aspects of C forward declarations */
8
9struct task_struct *__switch_to_asm(struct task_struct *prev,
10				    struct task_struct *next);
11
12__visible struct task_struct *__switch_to(struct task_struct *prev,
13					  struct task_struct *next);
14
15asmlinkage void ret_from_fork_asm(void);
16__visible void ret_from_fork(struct task_struct *prev, struct pt_regs *regs,
17			     int (*fn)(void *), void *fn_arg);
18
19/*
20 * This is the structure pointed to by thread.sp for an inactive task.  The
21 * order of the fields must match the code in __switch_to_asm().
22 */
23struct inactive_task_frame {
24#ifdef CONFIG_X86_64
25	unsigned long r15;
26	unsigned long r14;
27	unsigned long r13;
28	unsigned long r12;
29#else
30	unsigned long flags;
31	unsigned long si;
32	unsigned long di;
33#endif
34	unsigned long bx;
35
36	/*
37	 * These two fields must be together.  They form a stack frame header,
38	 * needed by get_frame_pointer().
39	 */
40	unsigned long bp;
41	unsigned long ret_addr;
42};
43
44struct fork_frame {
45	struct inactive_task_frame frame;
46	struct pt_regs regs;
47};
48
49#define switch_to(prev, next, last)					\
50do {									\
51	((last) = __switch_to_asm((prev), (next)));			\
52} while (0)
53
54#ifdef CONFIG_X86_32
55static inline void refresh_sysenter_cs(struct thread_struct *thread)
56{
57	/* Only happens when SEP is enabled, no need to test "SEP"arately: */
58	if (unlikely(this_cpu_read(cpu_tss_rw.x86_tss.ss1) == thread->sysenter_cs))
59		return;
60
61	this_cpu_write(cpu_tss_rw.x86_tss.ss1, thread->sysenter_cs);
62	wrmsr(MSR_IA32_SYSENTER_CS, thread->sysenter_cs, 0);
63}
64#endif
65
66/* This is used when switching tasks or entering/exiting vm86 mode. */
67static inline void update_task_stack(struct task_struct *task)
68{
69	/* sp0 always points to the entry trampoline stack, which is constant: */
70#ifdef CONFIG_X86_32
71	this_cpu_write(cpu_tss_rw.x86_tss.sp1, task->thread.sp0);
72#else
73	if (cpu_feature_enabled(X86_FEATURE_FRED)) {
74		/* WRMSRNS is a baseline feature for FRED. */
75		wrmsrns(MSR_IA32_FRED_RSP0, (unsigned long)task_stack_page(task) + THREAD_SIZE);
76	} else if (cpu_feature_enabled(X86_FEATURE_XENPV)) {
77		/* Xen PV enters the kernel on the thread stack. */
78		load_sp0(task_top_of_stack(task));
79	}
80#endif
81}
82
83static inline void kthread_frame_init(struct inactive_task_frame *frame,
84				      int (*fun)(void *), void *arg)
85{
86	frame->bx = (unsigned long)fun;
87#ifdef CONFIG_X86_32
88	frame->di = (unsigned long)arg;
89#else
90	frame->r12 = (unsigned long)arg;
91#endif
92}
93
94#endif /* _ASM_X86_SWITCH_TO_H */
95