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,unsigned long fun,unsigned long arg)80 static inline void kthread_frame_init(struct inactive_task_frame *frame,
81 unsigned long fun, unsigned long arg)
82 {
83 frame->bx = fun;
84 #ifdef CONFIG_X86_32
85 frame->di = arg;
86 #else
87 frame->r12 = arg;
88 #endif
89 }
90
91 #endif /* _ASM_X86_SWITCH_TO_H */
92