Linux x86_64 Kernel Interrupt initialization

Interrupt classification

In Linux systems, interrupts are divided into:

• Hard interrupt: An interrupt that is generated by an external device or that performs an exception that needs to be processed quickly. such as missing pages interrupt, timer hardware interrupt.

  Based on internal or external production, divided into:
  1. Exception: An exception is an internally generated interrupt that is not masked.
  2. External interrupts: External interrupts are generated by external devices and can be masked.

• Soft Interrupt:

? Soft interrupts are the bottom-half processing part of the Linux system interrupt processing and are interrupts of the Linux simulation. In order to speed up the processing of hardware interrupt, to prevent the loss of data, Linux interrupt processing is divided into the top half processing and the bottom half processing two parts, the top half processing program to quickly deal with hardware events, not so urgent logic in the end of the semi-processing program, you can simply think that the hard terminal processing program is the top half processing program, The soft interrupt handler is the bottom half handler. Soft interrupts are typically performed only after the hard interrupt handler is executed. However, when the hard interrupt is nested, the soft interrupt will be processed after all the hard interrupts are processed, and when the soft interrupt is too much, it will be processed in the KSOFTIRQD thread.

Kernel Initialization-Interrupt

Intel processors have 256 hard interrupt numbers. The first 32 interrupt numbers are used for exceptions and are initialized when the kernel is initialized. The kernel initialization code flow is as follows:
You can see that exception handling is initialized first, partial external interrupts are initialized, and part of the soft interrupt processing is initialized.

void __init start_kernel(void){         lock_kernel();    ...     //初始化调度模块    sched_init();    ...    sort_main_extable();    // 初始化异常处理。    trap_init();    ...    // 初始化外部中断    init_IRQ();    ...    // 初始化定时器模块，同时，会注册定时器的软中断处理函数。    init_timers();        // 初始化软中断）    softirq_init();    time_init();    ...    // 初始化    acpi_early_init();}

Exception Interrupt Initialization

An exception interrupt is called a trap in the kernel, and the exception interrupt initialization code is

//Gate initialization. Initializes the interrupt vector table. The system has a fixed 256 hardware interrupt vector. void__init Trap_init (void) {Set_intr_gate (0, &divide_error); Set_intr_gate_ist (1, &debug,debug_stack); Set_intr_gate_ist (2, &nmi,nmi_stack); Set_intr_gate (3, &INT3); Set_system_gate (4, &overflow);/ * int4-5 can called from all */Set_system_gate (5, &bounds); Set_intr_gate (6, &INVALID_OP); Set_intr_gate (7, &device_not_available); Set_intr_gate_ist (8, &double_fault, Doublefault_stack); Set_intr_gate (9, &coprocessor_segment_overrun); Set_intr_gate (Ten, &INVALID_TSS); Set_intr_gate ( One, &segment_not_present); Set_intr_gate_ist ( A, &stack_segment,stackfault_stack); Set_intr_gate ( -, &general_protection); Set_intr_gate ( -, &page_fault); Set_intr_gate ( the, &spurious_interrupt_bug); Set_intr_gate ( -, &coprocessor_error); Set_intr_gate ( -, &alignment_check);#ifdef CONFIG_X86_MCESet_intr_gate_ist ( -, &machine_check, Mce_stack);#endifSet_intr_gate ( +, &simd_coprocessor_error);#ifdef config_ia32_emulationSet_system_gate (Ia32_syscall_vector, Ia32_syscall);#endifSet_intr_gate (Kdb_vector, call_debug);/** Should is a barrier for any external CPU state.     */Cpu_init ();}

Summarized as follows:

Interrupt Vector Number	Exception Events	Linux Processing program
0	Division Error	Divide_error
1	debugging exceptions	Debug
2	NMI Interrupt	Nmi
3	Single byte, int 3	Int3
4	Overflow	Overflow
5	Boundary monitoring interrupted	Bounds
6	Invalid operation code	Invalid_op
7	Device Not available	Device_not_available
8	Double fault	Double_fault
9	Coprocessor Segment Overflow	Coprocessor_segment_overrun
10	Invalid TSS	Incalid_tss
11	Missing segment Interruption	Segment_not_present
12	Stack exception	Stack_segment
13	General Protection exceptions	General_protection
14	Page exception	Page_fault
15		Spurious_interrupt_bug
16	Coprocessor Error	Coprocessor_error
17	Alignment Check Interrupt	Alignment_check
0x80	System calls	Ia32_syscall
0xf9	Kernel debugging	Call_debug

The above interrupt processing functions are written in assembly language. Part of the assembly is processed directly, and part of it is handled by invoking the C function.
Assembly code in linux/arch/x86_64/entry.S , most of the call C function do_中断处理函数名 processing.
Tidy up as follows:

Interrupt Vector Number	Exception Events	Linux Compilation	Call C function	Processing Results
0	Division Error	Divide_error	Do_divide_error	Send SIGFPE Signal
1	debugging exceptions	Debug	Do_debug	Send Sigtrap Signal
2	NMI Interrupt	Nmi	Do_nmi
3	Single byte, int 3	Int3	Do_int3	Send Sigtrap Signal
4	Overflow	Overflow	Do_overflow	Send SIGSEGV Signal
5	Boundary monitoring interrupted	Bounds	Do_bounds	Send SIGSEGV Signal
6	Invalid operation code	Invalid_op	Do_invalid_op	Send Sigill Signal
7	Device Not available	Device_not_available	Math_state_restore	Send SIGSEGV Signal
8	Double fault	Double_fault	Do_double_fault
9	Coprocessor Segment Overflow	Coprocessor_segment_overrun	Do_coprocessor_segment_overrun	Send SIGFPE Signal
10	Invalid TSS	Invalid_tss	Do_invalid_tss	Send SIGSEGV Signal
11	Missing segment Interruption	Segment_not_present	Do_segment_not_present	Send Sigbus Signal
12	Stack exception	Stack_segment	Do_stack_segment
13	General Protection exceptions	General_protection	Do_general_protection
14	Page exception	Page_fault	Do_page_fault	Handling Missing pages interrupts
15		Spurious_interrupt_bug	Do_spurious_interrupt_bug
16	Coprocessor Error	Coprocessor_error	Do_coprocessor_error	Send SIGFPE Signal
17	Alignment Check Interrupt	Alignment_check	Do_alignment_check	Send Sigbus Signal
0x80	System calls	Ia32_syscall
0xf9	Kernel debugging	Call_debug	Do_call_debug

External interrupt Initialization

中断控制器硬件APIC分为两种：本地APIC和全局APIC。本地APIC集成在CPU内部，每个CPU都有一个，用于处理本地中断请求，CPU可以通过APIC向其他CPU发送中断，现在主要用于CPU之间的通信（IPI）。全局APIC主要是连接外部设备，用于外部设备的中断。在内核中断初始化的时候，会初始化三个与IPI相关中断。

void__init INIT_IRQ (void){intI/*** This function is mainly to initialize the hardware* 1. Initialize the local APIC control chip* 2. Initialize 8259A chip    /Init_isa_irqs ();    /** Empty the interrupt vector table after 32. (except for system calls and interrupt numbers for kernel debugging)     */     for(i =0; I < (nr_vectors-first_external_vector); i++) {intVector = First_external_vector + i;if(I >= Nr_irqs) Break;if(Vector! = ia32_syscall_vector && vector! = kdb_vector)    {set_intr_gate (vector, interrupt[i]); }    }//Multi-processor communication interrupt#ifdef CONFIG_SMPSet_intr_gate (First_device_vector, interrupt[0]);    Set_intr_gate (Reschedule_vector, reschedule_interrupt);    Set_intr_gate (Invalidate_tlb_vector, invalidate_interrupt); Set_intr_gate (Call_function_vector, call_function_interrupt);#endif//local APIC Interrupt#ifdef config_x86_local_apic    / * Self generated IPI for local APIC timer * /Set_intr_gate (Local_timer_vector, apic_timer_interrupt);    Set_intr_gate (Spurious_apic_vector, spurious_interrupt); Set_intr_gate (Error_apic_vector, error_interrupt);#endifSetup_timer ();if(!acpi_ioapic) Setup_irq (2, &AMP;IRQ2);}

Summarized as follows:

Interrupt Vector Number	Interrupt Name	Exception Events	Interrupt handler function	Call C function	Processing Results
0xFC	Reschedule_vector	Interrupts between processors, for classmates between CPUs, other CPUs require re-scheduling	Reschedule_interrupt	Smp_reschedule_interrupt	Set the thread dispatch flag to be re-dispatched. The thread is then re-dispatched when the kernel checks for flags
0xfd	Invalidate_tlb_vector	Interrupts between processors for inter-CPU communication, and other CPUs require TLB cache invalidation	Invalidate_interrupt	Smp_invalidate_interrupt	CPU Flush TLB
0xfa	Call_function_vector	Interrupts between processors for communication between CPUs, allowing additional CPUs to call a function	Call_function_interrupt	Smp_call_function_interrupt	The function data is passed through call_data_struct, and the CPU calls the function
0xEF	Local_timer_vector	APIC Timer Interrupt	Apic_timer_interrupt	Smp_apic_timer_interrupt	Soft Interrupt for Trigger timer
0xFF	Spurious_apic_vector	Pseudo Interrupt	Spurious_interrupt	Smp_spurious_interrupt	Ignore
0xFE	Error_apic_vector	APIC Error	Error_interrupt	Smp_error_interrupt	Print error

0XFA Interrupt Description:
When the CPU needs another CPU to execute a function, it only needs to initialize

struct call_data_struct {    void (*func) (void *info);    void *info;    atomic_t started;    atomic_t finished;    int wait;};

Structure, then issue a 0XFA interrupt.

Soft interrupt Initialization

Soft interrupt initialization is divided into two parts:

1. When the timer is initialized, the TIMER_SOFTIRQ soft interrupt is turned on and the interrupt handler is set to RUN_TIMER_SOFTIRQ.
2. The Softirq_init function executes, and the TASKLET_SOFTIRQ and HI_SOFTIRQ are opened, and the processing functions are tasklet_action and tasklet_hi_action respectively.

The threading mechanism for soft interrupts is not said.

Linux x86_64 Kernel Interrupt initialization