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 *prev,
20 struct task_struct *next)
22 #ifdef CONFIG_VMAP_STACK
24 * If we switch to a stack that has a top-level paging entry
25 * that is not present in the current mm, the resulting #PF will
26 * will be promoted to a double-fault and we'll panic. Probe
27 * the new stack now so that vmalloc_fault can fix up the page
28 * tables if needed. This can only happen if we use a stack
31 * We assume that the stack is aligned so that it never spans
32 * more than one top-level paging entry.
34 * To minimize cache pollution, just follow the stack pointer.
36 READ_ONCE(*(unsigned char *)next->thread.sp);
40 asmlinkage void ret_from_fork(void);
43 * This is the structure pointed to by thread.sp for an inactive task. The
44 * order of the fields must match the code in __switch_to_asm().
46 struct inactive_task_frame {
59 * These two fields must be together. They form a stack frame header,
60 * needed by get_frame_pointer().
63 unsigned long ret_addr;
67 struct inactive_task_frame frame;
71 #define switch_to(prev, next, last) \
73 prepare_switch_to(prev, next); \
75 ((last) = __switch_to_asm((prev), (next))); \
79 static inline void refresh_sysenter_cs(struct thread_struct *thread)
81 /* Only happens when SEP is enabled, no need to test "SEP"arately: */
82 if (unlikely(this_cpu_read(cpu_tss.x86_tss.ss1) == thread->sysenter_cs))
85 this_cpu_write(cpu_tss.x86_tss.ss1, thread->sysenter_cs);
86 wrmsr(MSR_IA32_SYSENTER_CS, thread->sysenter_cs, 0);
90 /* This is used when switching tasks or entering/exiting vm86 mode. */
91 static inline void update_sp0(struct task_struct *task)
94 load_sp0(task->thread.sp0);
96 load_sp0(task_top_of_stack(task));
100 #endif /* _ASM_X86_SWITCH_TO_H */