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 struct task_struct; /* one of the stranger aspects of C forward declarations */
   6
   7 struct task_struct *__switch_to_asm(struct task_struct *prev,
   8                                     struct task_struct *next);
   9
  10 __visible struct task_struct *__switch_to(struct task_struct *prev,
  11                                           struct task_struct *next);
  12 struct tss_struct;
  13 void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p,
  14                       struct tss_struct *tss);
  15
  16 /* This runs runs on the previous thread's stack. */
  17 static inline void prepare_switch_to(struct task_struct *prev,
  18                                      struct task_struct *next)
  19 {
  20 #ifdef CONFIG_VMAP_STACK
  21         /*
  22          * If we switch to a stack that has a top-level paging entry
  23          * that is not present in the current mm, the resulting #PF will
  24          * will be promoted to a double-fault and we'll panic.  Probe
  25          * the new stack now so that vmalloc_fault can fix up the page
  26          * tables if needed.  This can only happen if we use a stack
  27          * in vmap space.
  28          *
  29          * We assume that the stack is aligned so that it never spans
  30          * more than one top-level paging entry.
  31          *
  32          * To minimize cache pollution, just follow the stack pointer.
  33          */
  34         READ_ONCE(*(unsigned char *)next->thread.sp);
  35 #endif
  36 }
  37
  38 asmlinkage void ret_from_fork(void);
  39
  40 /*
  41  * This is the structure pointed to by thread.sp for an inactive task.  The
  42  * order of the fields must match the code in __switch_to_asm().
  43  */
  44 struct inactive_task_frame {
  45 #ifdef CONFIG_X86_64
  46         unsigned long r15;
  47         unsigned long r14;
  48         unsigned long r13;
  49         unsigned long r12;
  50 #else
  51         unsigned long si;
  52         unsigned long di;
  53 #endif
  54         unsigned long bx;
  55
  56         /*
  57          * These two fields must be together.  They form a stack frame header,
  58          * needed by get_frame_pointer().
  59          */
  60         unsigned long bp;
  61         unsigned long ret_addr;
  62 };
  63
  64 struct fork_frame {
  65         struct inactive_task_frame frame;
  66         struct pt_regs regs;
  67 };
  68
  69 #define switch_to(prev, next, last)                                     \
  70 do {                                                                    \
  71         prepare_switch_to(prev, next);                                  \
  72                                                                         \
  73         ((last) = __switch_to_asm((prev), (next)));                     \
  74 } while (0)
  75
  76 #endif /* _ASM_X86_SWITCH_TO_H */