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 struct tss_struct; 15 void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p, 16 struct tss_struct *tss); 17 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) 21 { 22 #ifdef CONFIG_VMAP_STACK 23 /* 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 29 * in vmap space. 30 * 31 * We assume that the stack is aligned so that it never spans 32 * more than one top-level paging entry. 33 * 34 * To minimize cache pollution, just follow the stack pointer. 35 */ 36 READ_ONCE(*(unsigned char *)next->thread.sp); 37 #endif 38 } 39 40 asmlinkage void ret_from_fork(void); 41 42 /* 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(). 45 */ 46 struct inactive_task_frame { 47 #ifdef CONFIG_X86_64 48 unsigned long r15; 49 unsigned long r14; 50 unsigned long r13; 51 unsigned long r12; 52 #else 53 unsigned long si; 54 unsigned long di; 55 #endif 56 unsigned long bx; 57 58 /* 59 * These two fields must be together. They form a stack frame header, 60 * needed by get_frame_pointer(). 61 */ 62 unsigned long bp; 63 unsigned long ret_addr; 64 }; 65 66 struct fork_frame { 67 struct inactive_task_frame frame; 68 struct pt_regs regs; 69 }; 70 71 #define switch_to(prev, next, last) \ 72 do { \ 73 prepare_switch_to(prev, next); \ 74 \ 75 ((last) = __switch_to_asm((prev), (next))); \ 76 } while (0) 77 78 #ifdef CONFIG_X86_32 79 static inline void refresh_sysenter_cs(struct thread_struct *thread) 80 { 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)) 83 return; 84 85 this_cpu_write(cpu_tss.x86_tss.ss1, thread->sysenter_cs); 86 wrmsr(MSR_IA32_SYSENTER_CS, thread->sysenter_cs, 0); 87 } 88 #endif 89 90 /* This is used when switching tasks or entering/exiting vm86 mode. */ 91 static inline void update_sp0(struct task_struct *task) 92 { 93 #ifdef CONFIG_X86_32 94 load_sp0(task->thread.sp0); 95 #else 96 load_sp0(task_top_of_stack(task)); 97 #endif 98 } 99 100 #endif /* _ASM_X86_SWITCH_TO_H */ 101