arch/x86/include/asm/switch_to.h

   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 */