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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _ASM_X86_SWITCH_TO_H
#define _ASM_X86_SWITCH_TO_H
#include <linux/sched/task_stack.h>
struct task_struct; /* one of the stranger aspects of C forward declarations */
struct task_struct *__switch_to_asm(struct task_struct *prev,
struct task_struct *next);
__visible struct task_struct *__switch_to(struct task_struct *prev,
struct task_struct *next);
/* This runs runs on the previous thread's stack. */
static inline void prepare_switch_to(struct task_struct *next)
{
#ifdef CONFIG_VMAP_STACK
/*
* If we switch to a stack that has a top-level paging entry
* that is not present in the current mm, the resulting #PF will
* will be promoted to a double-fault and we'll panic. Probe
* the new stack now so that vmalloc_fault can fix up the page
* tables if needed. This can only happen if we use a stack
* in vmap space.
*
* We assume that the stack is aligned so that it never spans
* more than one top-level paging entry.
*
* To minimize cache pollution, just follow the stack pointer.
*/
READ_ONCE(*(unsigned char *)next->thread.sp);
#endif
}
asmlinkage void ret_from_fork(void);
/*
* This is the structure pointed to by thread.sp for an inactive task. The
* order of the fields must match the code in __switch_to_asm().
*/
struct inactive_task_frame {
unsigned long flags;
#ifdef CONFIG_X86_64
unsigned long r15;
unsigned long r14;
unsigned long r13;
unsigned long r12;
#else
unsigned long si;
unsigned long di;
#endif
unsigned long bx;
/*
* These two fields must be together. They form a stack frame header,
* needed by get_frame_pointer().
*/
unsigned long bp;
unsigned long ret_addr;
};
struct fork_frame {
struct inactive_task_frame frame;
struct pt_regs regs;
};
#define switch_to(prev, next, last) \
do { \
prepare_switch_to(next); \
\
((last) = __switch_to_asm((prev), (next))); \
} while (0)
#ifdef CONFIG_X86_32
static inline void refresh_sysenter_cs(struct thread_struct *thread)
{
/* Only happens when SEP is enabled, no need to test "SEP"arately: */
if (unlikely(this_cpu_read(cpu_tss_rw.x86_tss.ss1) == thread->sysenter_cs))
return;
this_cpu_write(cpu_tss_rw.x86_tss.ss1, thread->sysenter_cs);
wrmsr(MSR_IA32_SYSENTER_CS, thread->sysenter_cs, 0);
}
#endif
/* This is used when switching tasks or entering/exiting vm86 mode. */
static inline void update_task_stack(struct task_struct *task)
{
/* sp0 always points to the entry trampoline stack, which is constant: */
#ifdef CONFIG_X86_32
if (static_cpu_has(X86_FEATURE_XENPV))
load_sp0(task->thread.sp0);
else
this_cpu_write(cpu_tss_rw.x86_tss.sp1, task->thread.sp0);
#else
/*
* x86-64 updates x86_tss.sp1 via cpu_current_top_of_stack. That
* doesn't work on x86-32 because sp1 and
* cpu_current_top_of_stack have different values (because of
* the non-zero stack-padding on 32bit).
*/
if (static_cpu_has(X86_FEATURE_XENPV))
load_sp0(task_top_of_stack(task));
#endif
}
#endif /* _ASM_X86_SWITCH_TO_H */
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