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 /* This runs runs on the previous thread's stack. */
16 static inline void prepare_switch_to(struct task_struct
*next
)
18 #ifdef CONFIG_VMAP_STACK
20 * If we switch to a stack that has a top-level paging entry
21 * that is not present in the current mm, the resulting #PF will
22 * will be promoted to a double-fault and we'll panic. Probe
23 * the new stack now so that vmalloc_fault can fix up the page
24 * tables if needed. This can only happen if we use a stack
27 * We assume that the stack is aligned so that it never spans
28 * more than one top-level paging entry.
30 * To minimize cache pollution, just follow the stack pointer.
32 READ_ONCE(*(unsigned char *)next
->thread
.sp
);
36 asmlinkage
void ret_from_fork(void);
39 * This is the structure pointed to by thread.sp for an inactive task. The
40 * order of the fields must match the code in __switch_to_asm().
42 struct inactive_task_frame
{
56 * These two fields must be together. They form a stack frame header,
57 * needed by get_frame_pointer().
60 unsigned long ret_addr
;
64 struct inactive_task_frame frame
;
68 #define switch_to(prev, next, last) \
70 prepare_switch_to(next); \
72 ((last) = __switch_to_asm((prev), (next))); \
76 static inline void refresh_sysenter_cs(struct thread_struct
*thread
)
78 /* Only happens when SEP is enabled, no need to test "SEP"arately: */
79 if (unlikely(this_cpu_read(cpu_tss_rw
.x86_tss
.ss1
) == thread
->sysenter_cs
))
82 this_cpu_write(cpu_tss_rw
.x86_tss
.ss1
, thread
->sysenter_cs
);
83 wrmsr(MSR_IA32_SYSENTER_CS
, thread
->sysenter_cs
, 0);
87 /* This is used when switching tasks or entering/exiting vm86 mode. */
88 static inline void update_task_stack(struct task_struct
*task
)
90 /* sp0 always points to the entry trampoline stack, which is constant: */
92 if (static_cpu_has(X86_FEATURE_XENPV
))
93 load_sp0(task
->thread
.sp0
);
95 this_cpu_write(cpu_tss_rw
.x86_tss
.sp1
, task
->thread
.sp0
);
98 * x86-64 updates x86_tss.sp1 via cpu_current_top_of_stack. That
99 * doesn't work on x86-32 because sp1 and
100 * cpu_current_top_of_stack have different values (because of
101 * the non-zero stack-padding on 32bit).
103 if (static_cpu_has(X86_FEATURE_XENPV
))
104 load_sp0(task_top_of_stack(task
));
108 static inline void kthread_frame_init(struct inactive_task_frame
*frame
,
109 unsigned long fun
, unsigned long arg
)
119 #endif /* _ASM_X86_SWITCH_TO_H */