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 /* data that is pointed to by thread.sp */
  40 struct inactive_task_frame {
  41 #ifdef CONFIG_X86_64
  42         unsigned long r15;
  43         unsigned long r14;
  44         unsigned long r13;
  45         unsigned long r12;
  46 #else
  47         unsigned long si;
  48         unsigned long di;
  49 #endif
  50         unsigned long bx;
  51         unsigned long bp;
  52         unsigned long ret_addr;
  53 };
  54
  55 struct fork_frame {
  56         struct inactive_task_frame frame;
  57         struct pt_regs regs;
  58 };
  59
  60 #define switch_to(prev, next, last)                                     \
  61 do {                                                                    \
  62         prepare_switch_to(prev, next);                                  \
  63                                                                         \
  64         ((last) = __switch_to_asm((prev), (next)));                     \
  65 } while (0)
  66
  67 #endif /* _ASM_X86_SWITCH_TO_H */