switch_to.h

 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
55#include <asm/msr.h>
56
57static inline void refresh_sysenter_cs(struct thread_struct *thread)
58{
59	/* Only happens when SEP is enabled, no need to test "SEP"arately: */
60	if (unlikely(this_cpu_read(cpu_tss_rw.x86_tss.ss1) == thread->sysenter_cs))
61		return;
62
63	this_cpu_write(cpu_tss_rw.x86_tss.ss1, thread->sysenter_cs);
64	wrmsrq(MSR_IA32_SYSENTER_CS, thread->sysenter_cs);
65}
66#endif
67
68/* This is used when switching tasks or entering/exiting vm86 mode. */
69static inline void update_task_stack(struct task_struct *task)
70{
71	/* sp0 always points to the entry trampoline stack, which is constant: */
72#ifdef CONFIG_X86_32
73	this_cpu_write(cpu_tss_rw.x86_tss.sp1, task->thread.sp0);
74#else
75	if (!cpu_feature_enabled(X86_FEATURE_FRED) && cpu_feature_enabled(X86_FEATURE_XENPV))
76		/* Xen PV enters the kernel on the thread stack. */
77		load_sp0(task_top_of_stack(task));
78#endif
79}
80
81static inline void kthread_frame_init(struct inactive_task_frame *frame,
82				      int (*fun)(void *), void *arg)
83{
84	frame->bx = (unsigned long)fun;
85#ifdef CONFIG_X86_32
86	frame->di = (unsigned long)arg;
87#else
88	frame->r12 = (unsigned long)arg;
89#endif
90}
91
92#endif /* _ASM_X86_SWITCH_TO_H */