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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 : : /* This runs runs on the previous thread's stack. */ 16 : : static inline void prepare_switch_to(struct task_struct *next) 17 : : { 18 : : #ifdef CONFIG_VMAP_STACK 19 : : /* 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 25 : : * in vmap space. 26 : : * 27 : : * We assume that the stack is aligned so that it never spans 28 : : * more than one top-level paging entry. 29 : : * 30 : : * To minimize cache pollution, just follow the stack pointer. 31 : : */ 32 : : READ_ONCE(*(unsigned char *)next->thread.sp); 33 : : #endif 34 : : } 35 : : 36 : : asmlinkage void ret_from_fork(void); 37 : : 38 : : /* 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(). 41 : : */ 42 : : struct inactive_task_frame { 43 : : #ifdef CONFIG_X86_64 44 : : unsigned long r15; 45 : : unsigned long r14; 46 : : unsigned long r13; 47 : : unsigned long r12; 48 : : #else 49 : : unsigned long flags; 50 : : unsigned long si; 51 : : unsigned long di; 52 : : #endif 53 : : unsigned long bx; 54 : : 55 : : /* 56 : : * These two fields must be together. They form a stack frame header, 57 : : * needed by get_frame_pointer(). 58 : : */ 59 : : unsigned long bp; 60 : : unsigned long ret_addr; 61 : : }; 62 : : 63 : : struct fork_frame { 64 : : struct inactive_task_frame frame; 65 : : struct pt_regs regs; 66 : : }; 67 : : 68 : : #define switch_to(prev, next, last) \ 69 : : do { \ 70 : : prepare_switch_to(next); \ 71 : : \ 72 : : ((last) = __switch_to_asm((prev), (next))); \ 73 : : } while (0) 74 : : 75 : : #ifdef CONFIG_X86_32 76 : : static inline void refresh_sysenter_cs(struct thread_struct *thread) 77 : : { 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)) 80 : : return; 81 : : 82 : : this_cpu_write(cpu_tss_rw.x86_tss.ss1, thread->sysenter_cs); 83 : : wrmsr(MSR_IA32_SYSENTER_CS, thread->sysenter_cs, 0); 84 : : } 85 : : #endif 86 : : 87 : : /* This is used when switching tasks or entering/exiting vm86 mode. */ 88 : 296002 : static inline void update_task_stack(struct task_struct *task) 89 : : { 90 : : /* sp0 always points to the entry trampoline stack, which is constant: */ 91 : : #ifdef CONFIG_X86_32 92 : : if (static_cpu_has(X86_FEATURE_XENPV)) 93 : : load_sp0(task->thread.sp0); 94 : : else 95 : : this_cpu_write(cpu_tss_rw.x86_tss.sp1, task->thread.sp0); 96 : : #else 97 : : /* 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). 102 : : */ 103 [ - - + ]: 296002 : if (static_cpu_has(X86_FEATURE_XENPV)) 104 : 0 : load_sp0(task_top_of_stack(task)); 105 : : #endif 106 : 296002 : } 107 : : 108 : 1144 : static inline void kthread_frame_init(struct inactive_task_frame *frame, 109 : : unsigned long fun, unsigned long arg) 110 : : { 111 : 1144 : frame->bx = fun; 112 : : #ifdef CONFIG_X86_32 113 : : frame->di = arg; 114 : : #else 115 : 1144 : frame->r12 = arg; 116 : : #endif 117 : : } 118 : : 119 : : #endif /* _ASM_X86_SWITCH_TO_H */