| b.liu | e958203 | 2025-04-17 19:18:16 +0800 | [diff] [blame^] | 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 | |
| 7 | struct task_struct; /* one of the stranger aspects of C forward declarations */ |
| 8 | |
| 9 | struct 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 | |
| 15 | /* This runs runs on the previous thread's stack. */ |
| 16 | static inline void prepare_switch_to(struct task_struct *next) |
| 17 | { |
| 18 | #ifdef CONFIG_VMAP_STACK |
| 19 | /* |
| 20 | * If we switch to a stack that has a top-level paging entry |
| 21 | * that is not present in the current mm, the resulting #PF will |
| 22 | * will be promoted to a double-fault and we'll panic. Probe |
| 23 | * the new stack now so that vmalloc_fault can fix up the page |
| 24 | * tables if needed. This can only happen if we use a stack |
| 25 | * in vmap space. |
| 26 | * |
| 27 | * We assume that the stack is aligned so that it never spans |
| 28 | * more than one top-level paging entry. |
| 29 | * |
| 30 | * To minimize cache pollution, just follow the stack pointer. |
| 31 | */ |
| 32 | READ_ONCE(*(unsigned char *)next->thread.sp); |
| 33 | #endif |
| 34 | } |
| 35 | |
| 36 | asmlinkage void ret_from_fork(void); |
| 37 | |
| 38 | /* |
| 39 | * This is the structure pointed to by thread.sp for an inactive task. The |
| 40 | * order of the fields must match the code in __switch_to_asm(). |
| 41 | */ |
| 42 | struct inactive_task_frame { |
| 43 | #ifdef CONFIG_X86_64 |
| 44 | unsigned long r15; |
| 45 | unsigned long r14; |
| 46 | unsigned long r13; |
| 47 | unsigned long r12; |
| 48 | #else |
| 49 | unsigned long flags; |
| 50 | unsigned long si; |
| 51 | unsigned long di; |
| 52 | #endif |
| 53 | unsigned long bx; |
| 54 | |
| 55 | /* |
| 56 | * These two fields must be together. They form a stack frame header, |
| 57 | * needed by get_frame_pointer(). |
| 58 | */ |
| 59 | unsigned long bp; |
| 60 | unsigned long ret_addr; |
| 61 | }; |
| 62 | |
| 63 | struct fork_frame { |
| 64 | struct inactive_task_frame frame; |
| 65 | struct pt_regs regs; |
| 66 | }; |
| 67 | |
| 68 | #define switch_to(prev, next, last) \ |
| 69 | do { \ |
| 70 | prepare_switch_to(next); \ |
| 71 | \ |
| 72 | ((last) = __switch_to_asm((prev), (next))); \ |
| 73 | } while (0) |
| 74 | |
| 75 | #ifdef CONFIG_X86_32 |
| 76 | static inline void refresh_sysenter_cs(struct thread_struct *thread) |
| 77 | { |
| 78 | /* Only happens when SEP is enabled, no need to test "SEP"arately: */ |
| 79 | if (unlikely(this_cpu_read(cpu_tss_rw.x86_tss.ss1) == thread->sysenter_cs)) |
| 80 | return; |
| 81 | |
| 82 | this_cpu_write(cpu_tss_rw.x86_tss.ss1, thread->sysenter_cs); |
| 83 | wrmsr(MSR_IA32_SYSENTER_CS, thread->sysenter_cs, 0); |
| 84 | } |
| 85 | #endif |
| 86 | |
| 87 | /* This is used when switching tasks or entering/exiting vm86 mode. */ |
| 88 | static inline void update_task_stack(struct task_struct *task) |
| 89 | { |
| 90 | /* sp0 always points to the entry trampoline stack, which is constant: */ |
| 91 | #ifdef CONFIG_X86_32 |
| 92 | if (static_cpu_has(X86_FEATURE_XENPV)) |
| 93 | load_sp0(task->thread.sp0); |
| 94 | else |
| 95 | this_cpu_write(cpu_tss_rw.x86_tss.sp1, task->thread.sp0); |
| 96 | #else |
| 97 | /* |
| 98 | * x86-64 updates x86_tss.sp1 via cpu_current_top_of_stack. That |
| 99 | * doesn't work on x86-32 because sp1 and |
| 100 | * cpu_current_top_of_stack have different values (because of |
| 101 | * the non-zero stack-padding on 32bit). |
| 102 | */ |
| 103 | if (static_cpu_has(X86_FEATURE_XENPV)) |
| 104 | load_sp0(task_top_of_stack(task)); |
| 105 | #endif |
| 106 | |
| 107 | } |
| 108 | |
| 109 | #endif /* _ASM_X86_SWITCH_TO_H */ |