1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _ASM_X86_SWITCH_TO_H
3 #define _ASM_X86_SWITCH_TO_H
5 #include <linux/sched/task_stack.h>
7 struct task_struct; /* one of the stranger aspects of C forward declarations */
9 struct task_struct *__switch_to_asm(struct task_struct *prev,
10 struct task_struct *next);
12 __visible struct task_struct *__switch_to(struct task_struct *prev,
13 struct task_struct *next);
15 void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p,
16 struct tss_struct *tss);
18 /* This runs runs on the previous thread's stack. */
19 static inline void prepare_switch_to(struct task_struct *next)
21 #ifdef CONFIG_VMAP_STACK
23 * If we switch to a stack that has a top-level paging entry
24 * that is not present in the current mm, the resulting #PF will
25 * will be promoted to a double-fault and we'll panic. Probe
26 * the new stack now so that vmalloc_fault can fix up the page
27 * tables if needed. This can only happen if we use a stack
30 * We assume that the stack is aligned so that it never spans
31 * more than one top-level paging entry.
33 * To minimize cache pollution, just follow the stack pointer.
35 READ_ONCE(*(unsigned char *)next->thread.sp);
39 asmlinkage void ret_from_fork(void);
42 * This is the structure pointed to by thread.sp for an inactive task. The
43 * order of the fields must match the code in __switch_to_asm().
45 struct inactive_task_frame {
58 * These two fields must be together. They form a stack frame header,
59 * needed by get_frame_pointer().
62 unsigned long ret_addr;
66 struct inactive_task_frame frame;
70 #define switch_to(prev, next, last) \
72 prepare_switch_to(next); \
74 ((last) = __switch_to_asm((prev), (next))); \
78 static inline void refresh_sysenter_cs(struct thread_struct *thread)
80 /* Only happens when SEP is enabled, no need to test "SEP"arately: */
81 if (unlikely(this_cpu_read(cpu_tss_rw.x86_tss.ss1) == thread->sysenter_cs))
84 this_cpu_write(cpu_tss_rw.x86_tss.ss1, thread->sysenter_cs);
85 wrmsr(MSR_IA32_SYSENTER_CS, thread->sysenter_cs, 0);
89 /* This is used when switching tasks or entering/exiting vm86 mode. */
90 static inline void update_sp0(struct task_struct *task)
92 /* On x86_64, sp0 always points to the entry trampoline stack, which is constant: */
94 load_sp0(task->thread.sp0);
96 if (static_cpu_has(X86_FEATURE_XENPV))
97 load_sp0(task_top_of_stack(task));
101 #endif /* _ASM_X86_SWITCH_TO_H */