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 if (static_cpu_has(X86_FEATURE_XENPV)) 70 load_sp0(task->thread.sp0); 71 else 72 this_cpu_write(cpu_tss_rw.x86_tss.sp1, task->thread.sp0); 73 #else 74 /* 75 * x86-64 updates x86_tss.sp1 via cpu_current_top_of_stack. That 76 * doesn't work on x86-32 because sp1 and 77 * cpu_current_top_of_stack have different values (because of 78 * the non-zero stack-padding on 32bit). 79 */ 80 if (static_cpu_has(X86_FEATURE_XENPV)) 81 load_sp0(task_top_of_stack(task)); 82 #endif 83 } 84 85 static inline void kthread_frame_init(struct inactive_task_frame *frame, 86 unsigned long fun, unsigned long arg) 87 { 88 frame->bx = fun; 89 #ifdef CONFIG_X86_32 90 frame->di = arg; 91 #else 92 frame->r12 = arg; 93 #endif 94 } 95 96 #endif /* _ASM_X86_SWITCH_TO_H */ 97