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
  12 /* This runs runs on the previous thread's stack. */
  13 static inline void prepare_switch_to(struct task_struct *prev,
  14                                      struct task_struct *next)
  15 {
  16 #ifdef CONFIG_VMAP_STACK
  17         /*
  18          * If we switch to a stack that has a top-level paging entry
  19          * that is not present in the current mm, the resulting #PF will
  20          * will be promoted to a double-fault and we'll panic.  Probe
  21          * the new stack now so that vmalloc_fault can fix up the page
  22          * tables if needed.  This can only happen if we use a stack
  23          * in vmap space.
  24          *
  25          * We assume that the stack is aligned so that it never spans
  26          * more than one top-level paging entry.
  27          *
  28          * To minimize cache pollution, just follow the stack pointer.
  29          */
  30         READ_ONCE(*(unsigned char *)next->thread.sp);
  31 #endif
  32 }
  33
  34 asmlinkage void ret_from_fork(void);
  35
  36 /* data that is pointed to by thread.sp */
  37 struct inactive_task_frame {
  38         unsigned long flags;
  39 #ifdef CONFIG_X86_64
  40         unsigned long r15;
  41         unsigned long r14;
  42         unsigned long r13;
  43         unsigned long r12;
  44 #else
  45         unsigned long si;
  46         unsigned long di;
  47 #endif
  48         unsigned long bx;
  49         unsigned long bp;
  50         unsigned long ret_addr;
  51 };
  52
  53 struct fork_frame {
  54         struct inactive_task_frame frame;
  55         struct pt_regs regs;
  56 };
  57
  58 #define switch_to(prev, next, last)                                     \
  59 do {                                                                    \
  60         prepare_switch_to(prev, next);                                  \
  61                                                                         \
  62         ((last) = __switch_to_asm((prev), (next)));                     \
  63 } while (0)
  64
  65 #endif /* _ASM_X86_SWITCH_TO_H */