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 asmlinkage void ret_from_fork(void); 16 17 /* 18 * This is the structure pointed to by thread.sp for an inactive task. The 19 * order of the fields must match the code in __switch_to_asm(). 20 */ 21 struct inactive_task_frame { 22 #ifdef CONFIG_X86_64 23 unsigned long r15; 24 unsigned long r14; 25 unsigned long r13; 26 unsigned long r12; 27 #else 28 unsigned long flags; 29 unsigned long si; 30 unsigned long di; 31 #endif 32 unsigned long bx; 33 34 /* 35 * These two fields must be together. They form a stack frame header, 36 * needed by get_frame_pointer(). 37 */ 38 unsigned long bp; 39 unsigned long ret_addr; 40 }; 41 42 struct fork_frame { 43 struct inactive_task_frame frame; 44 struct pt_regs regs; 45 }; 46 47 #define switch_to(prev, next, last) \ 48 do { \ 49 ((last) = __switch_to_asm((prev), (next))); \ 50 } while (0) 51 52 #ifdef CONFIG_X86_32 53 static inline void refresh_sysenter_cs(struct thread_struct *thread) 54 { 55 /* Only happens when SEP is enabled, no need to test "SEP"arately: */ 56 if (unlikely(this_cpu_read(cpu_tss_rw.x86_tss.ss1) == thread->sysenter_cs)) 57 return; 58 59 this_cpu_write(cpu_tss_rw.x86_tss.ss1, thread->sysenter_cs); 60 wrmsr(MSR_IA32_SYSENTER_CS, thread->sysenter_cs, 0); 61 } 62 #endif 63 64 /* This is used when switching tasks or entering/exiting vm86 mode. */ 65 static inline void update_task_stack(struct task_struct *task) 66 { 67 /* sp0 always points to the entry trampoline stack, which is constant: */ 68 #ifdef CONFIG_X86_32 69 this_cpu_write(cpu_tss_rw.x86_tss.sp1, task->thread.sp0); 70 #else 71 /* Xen PV enters the kernel on the thread stack. */ 72 if (cpu_feature_enabled(X86_FEATURE_XENPV)) 73 load_sp0(task_top_of_stack(task)); 74 #endif 75 } 76 77 static inline void kthread_frame_init(struct inactive_task_frame *frame, 78 int (*fun)(void *), void *arg) 79 { 80 frame->bx = (unsigned long)fun; 81 #ifdef CONFIG_X86_32 82 frame->di = (unsigned long)arg; 83 #else 84 frame->r12 = (unsigned long)arg; 85 #endif 86 } 87 88 #endif /* _ASM_X86_SWITCH_TO_H */ 89