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_asm(void); 16 __visible void ret_from_fork(struct task_struct *prev, struct pt_regs *regs, 17 int (*fn)(void *), void *fn_arg); 18 19 /* 20 * This is the structure pointed to by thread.sp for an inactive task. The 21 * order of the fields must match the code in __switch_to_asm(). 22 */ 23 struct inactive_task_frame { 24 #ifdef CONFIG_X86_64 25 unsigned long r15; 26 unsigned long r14; 27 unsigned long r13; 28 unsigned long r12; 29 #else 30 unsigned long flags; 31 unsigned long si; 32 unsigned long di; 33 #endif 34 unsigned long bx; 35 36 /* 37 * These two fields must be together. They form a stack frame header, 38 * needed by get_frame_pointer(). 39 */ 40 unsigned long bp; 41 unsigned long ret_addr; 42 }; 43 44 struct fork_frame { 45 struct inactive_task_frame frame; 46 struct pt_regs regs; 47 }; 48 49 #define switch_to(prev, next, last) \ 50 do { \ 51 ((last) = __switch_to_asm((prev), (next))); \ 52 } while (0) 53 54 #ifdef CONFIG_X86_32 55 static inline void refresh_sysenter_cs(struct thread_struct *thread) 56 { 57 /* Only happens when SEP is enabled, no need to test "SEP"arately: */ 58 if (unlikely(this_cpu_read(cpu_tss_rw.x86_tss.ss1) == thread->sysenter_cs)) 59 return; 60 61 this_cpu_write(cpu_tss_rw.x86_tss.ss1, thread->sysenter_cs); 62 wrmsr(MSR_IA32_SYSENTER_CS, thread->sysenter_cs, 0); 63 } 64 #endif 65 66 /* This is used when switching tasks or entering/exiting vm86 mode. */ 67 static inline void update_task_stack(struct task_struct *task) 68 { 69 /* sp0 always points to the entry trampoline stack, which is constant: */ 70 #ifdef CONFIG_X86_32 71 this_cpu_write(cpu_tss_rw.x86_tss.sp1, task->thread.sp0); 72 #else 73 if (cpu_feature_enabled(X86_FEATURE_FRED)) { 74 /* WRMSRNS is a baseline feature for FRED. */ 75 wrmsrns(MSR_IA32_FRED_RSP0, (unsigned long)task_stack_page(task) + THREAD_SIZE); 76 } else if (cpu_feature_enabled(X86_FEATURE_XENPV)) { 77 /* Xen PV enters the kernel on the thread stack. */ 78 load_sp0(task_top_of_stack(task)); 79 } 80 #endif 81 } 82 83 static inline void kthread_frame_init(struct inactive_task_frame *frame, 84 int (*fun)(void *), void *arg) 85 { 86 frame->bx = (unsigned long)fun; 87 #ifdef CONFIG_X86_32 88 frame->di = (unsigned long)arg; 89 #else 90 frame->r12 = (unsigned long)arg; 91 #endif 92 } 93 94 #endif /* _ASM_X86_SWITCH_TO_H */ 95