LXR linux/arch/x86/include/asm/switch

   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
   7struct task_struct; /* one of the stranger aspects of C forward declarations */
   8
   9struct 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
  15asmlinkage 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 */
  21struct 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
  42struct fork_frame {
  43        struct inactive_task_frame frame;
  44        struct pt_regs regs;
  45};
  46
  47#define switch_to(prev, next, last)                                     \
  48do {                                                                    \
  49        ((last) = __switch_to_asm((prev), (next)));                     \
  50} while (0)
  51
  52#ifdef CONFIG_X86_32
  53static 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. */
  65static 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        /* Xen PV enters the kernel on the thread stack. */
  75        if (static_cpu_has(X86_FEATURE_XENPV))
  76                load_sp0(task_top_of_stack(task));
  77#endif
  78}
  79
  80static inline void kthread_frame_init(struct inactive_task_frame *frame,
  81                                      unsigned long fun, unsigned long arg)
  82{
  83        frame->bx = fun;
  84#ifdef CONFIG_X86_32
  85        frame->di = arg;
  86#else
  87        frame->r12 = arg;
  88#endif
  89}
  90
  91#endif /* _ASM_X86_SWITCH_TO_H */
  92