arch/x86/include/asm/switch_to.h

   1 #ifndef _ASM_X86_SWITCH_TO_H
   2 #define _ASM_X86_SWITCH_TO_H
   3
   4 struct task_struct; /* one of the stranger aspects of C forward declarations */
   5
   6 struct task_struct *__switch_to_asm(struct task_struct *prev,
   7                                     struct task_struct *next);
   8
   9 __visible struct task_struct *__switch_to(struct task_struct *prev,
  10                                           struct task_struct *next);
  11 struct tss_struct;
  12 void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p,
  13                       struct tss_struct *tss);
  14
  15 /* This runs runs on the previous thread's stack. */
  16 static inline void prepare_switch_to(struct task_struct *prev,
  17                                      struct task_struct *next)
  18 {
  19 #ifdef CONFIG_VMAP_STACK
  20         /*
  21          * If we switch to a stack that has a top-level paging entry
  22          * that is not present in the current mm, the resulting #PF will
  23          * will be promoted to a double-fault and we'll panic.  Probe
  24          * the new stack now so that vmalloc_fault can fix up the page
  25          * tables if needed.  This can only happen if we use a stack
  26          * in vmap space.
  27          *
  28          * We assume that the stack is aligned so that it never spans
  29          * more than one top-level paging entry.
  30          *
  31          * To minimize cache pollution, just follow the stack pointer.
  32          */
  33         READ_ONCE(*(unsigned char *)next->thread.sp);
  34 #endif
  35 }
  36
  37 asmlinkage void ret_from_fork(void);
  38
  39 /*
  40  * This is the structure pointed to by thread.sp for an inactive task.  The
  41  * order of the fields must match the code in __switch_to_asm().
  42  */
  43 struct inactive_task_frame {
  44 #ifdef CONFIG_X86_64
  45         unsigned long r15;
  46         unsigned long r14;
  47         unsigned long r13;
  48         unsigned long r12;
  49 #else
  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(prev, next);                                  \
  71                                                                         \
  72         ((last) = __switch_to_asm((prev), (next)));                     \
  73 } while (0)
  74
  75 #endif /* _ASM_X86_SWITCH_TO_H */