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_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 */
23 struct 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
44 struct fork_frame {
45 struct inactive_task_frame frame;
46 struct pt_regs regs;
47 };
48
49 #define switch_to(prev, next, last) \
50 do { \
51 ((last) = __switch_to_asm((prev), (next))); \
52 } while (0)
53
54 #ifdef CONFIG_X86_32
55 static 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. */
67 static 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
83 static 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
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