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