--- /dev/null
+#define __ASM__
+#include <sys/hart.h>
+#include <sys/abi.h>
+#include <sys/interrupt32.S.inc>
+
+#include <lunaix/syscall.h>
+
+#define tss_esp0_off 4
+#define __ASM_INTR_DIAGNOSIS
+
+#ifdef __ASM_INTR_DIAGNOSIS
+.section .bss
+ .global debug_resv
+ debug_resv:
+ .skip 16
+ tmp_store:
+ .skip 4
+#endif
+
+.section .bss
+ .align 16
+ lo_tmp_stack:
+ .skip 256
+ tmp_stack:
+
+/*
+ This perhaps the ugliest part in the project.
+ It contains code to handle arbitrary depth of
+ nested interrupt and all those corner cases and
+ nasty gotchas.
+
+ Be aware the twists, offsets and hidden dependencies!
+
+*/
+
+.section .text
+ .type interrupt_wrapper, @function
+ .global interrupt_wrapper
+ interrupt_wrapper:
+ cld
+
+ subl $4, %esp # prealloc slot for parent linkage
+ pushl %esp
+
+ subl $16, %esp
+ movw %gs, 12(%esp)
+ movw %fs, 8(%esp)
+ movw %es, 4(%esp)
+ movw %ds, (%esp)
+
+ pushl %esi
+ pushl %ebp
+ pushl %edi
+ pushl %edx
+ pushl %ecx
+ pushl %ebx
+ pushl %eax
+
+ pushl $0 // placeholder for depth accounting
+
+ movl ics(%esp), %eax /* 取出 %cs */
+ andl $0x3, %eax /* 判断 RPL */
+ jz 1f
+
+ /* crossing the user/kernel boundary */
+ movw $KDATA_SEG, %ax
+ movw %ax, %gs
+ movw %ax, %fs
+ movw %ax, %ds
+ movw %ax, %es
+
+ movl current_thread, %ebx
+ movl iuesp(%esp), %eax
+
+ # Save x87 context to user stack, rather than kernel's memory.
+ # XXX what will happen if we triggered a page fault during fxsave?
+ # FIXME I think we should defer this to scheduler, and pratice lazy save/load
+ # Doing this will also make it safe from nested interrupt due to potential
+ # page fault when saving
+ # FIXME Also, generalise it to any FPU context, without constraining it to x87.
+
+ #andl $stack_alignment, %eax
+ #subl $512, %eax
+ #fxsave (%eax)
+
+ # 保存用户栈顶指针。因为我们允许同级中断的产生，所以需要该手段跟踪用户栈的地址。
+ movl %eax, thread_ustack_top(%ebx) # 存入__current->ustack_top
+
+ /* kernel space same-level switch */
+ 1:
+ movl %esp, %eax
+ andl $stack_alignment, %esp
+ subl $16, %esp
+ movl %eax, (%esp)
+
+ xorl %ebp, %ebp # marks the boundary of stack walking
+ call intr_handler
+
+ movl (%esp), %eax
+
+ .global soft_iret
+ soft_iret:
+ movl %eax, %esp
+
+#ifdef __ASM_INTR_DIAGNOSIS
+ movl %eax, (debug_resv + 8)
+ movl iesp(%esp), %eax
+ movl exeip(%eax), %eax
+ movl %eax, (debug_resv + 4) # eip
+#endif
+
+ movl ics(%esp), %eax
+ andl $3, %eax
+ jz 1f
+
+ # # FIXME x87 fpu context
+ # movl current_thread, %eax
+ # movl thread_ustack_top(%eax), %eax
+ # test %eax, %eax
+ # jz 1f
+ # fxrstor (%eax)
+
+1:
+ popl %eax # discard struct hart_state::depth
+ popl %eax
+ popl %ebx
+ popl %ecx
+ popl %edx
+ popl %edi
+ popl %ebp
+ popl %esi
+
+ movw (%esp), %ds
+ movw 4(%esp), %es
+ movw 8(%esp), %fs
+ movw 12(%esp), %gs
+
+ movl 16(%esp), %esp
+
+ movl %eax, tmp_store
+ movl current_thread, %eax
+
+ # nested intr: restore saved context
+ popl thread_hstate(%eax)
+
+ addl $8, %esp
+
+#ifdef __ASM_INTR_DIAGNOSIS
+ movl (%esp), %eax
+ movl %eax, debug_resv
+#endif
+ # 处理TSS.ESP的一些边界条件。如果是正常iret（即从内核模式*优雅地*退出）
+ # 那么TSS.ESP0应该为iret进行弹栈后，%esp的值。
+ # 所以这里的边界条件是：如返回用户模式，iret会额外弹出8个字节（ss,esp）
+ movl 4(%esp), %eax
+ andl $3, %eax
+ setnz %al
+ shll $3, %eax
+ addl $12, %eax
+ addl %esp, %eax
+ movl %eax, (_tss + tss_esp0_off)
+ movl tmp_store, %eax
+
+ iret
+
+ .type do_switch, @function
+ .global do_switch
+ do_switch:
+ # Assumption: __current already hold the target process
+
+ call proc_vmroot
+
+ movl %eax, %ebx
+ movl %cr3, %eax
+ xorl %ebx, %eax # avoid setting cr3 if just local thread switch.
+ jz 1f
+
+ movl %ebx, %cr3
+
+ 1:
+ # the address space could be changed. A temporary stack
+ # is required to prevent corrupt existing stack
+ movl $tmp_stack, %esp
+
+ call signal_dispatch # kernel/signal.c
+
+ movl current_thread, %ebx
+ test %eax, %eax # do we have signal to handle?
+ jz 1f
+
+ /*
+ 将tss.esp0设置为上次调度前的esp值。
+ 当处理信号时，上下文信息是不会恢复的，而是保存在用户栈中，然后直接跳转进位于用户空间的sig_wrapper进行
+ 信号的处理。当用户自定义的信号处理函数返回时，sigreturn的系统调用才开始进行上下文的恢复（或者说是进行
+ 另一次调度。
+ 由于这中间没有进行地址空间的交换，所以第二次跳转使用的是同一个内核栈，而之前默认tss.esp0的值是永远指向最顶部
+ 这样一来就有可能会覆盖更早的上下文信息（比如嵌套的信号捕获函数）
+ */
+ pushl %eax
+ call update_tss
+
+ popl %eax
+ jmp handle_signal
+
+ 1:
+ movl thread_hstate(%ebx), %eax
+ jmp soft_iret
+
+ .type handle_signal, @function
+ .global handle_signal
+ handle_signal:
+ # 注意1：任何对proc_sig的布局改动，都须及时的保证这里的一致性！
+ # 注意2：handle_signal在调用之前，须确保proc_sig已经写入用户栈！
+ # arg1 in %eax: addr of proc_sig structure in user stack
+ movl psig_saved_hstate(%eax), %ebx # %ebx = &proc_sig->saved_hstate
+
+ pushl $UDATA_SEG
+ pushl %eax # esp
+
+ movl iexecp(%ebx), %ebx
+ pushl exeflags(%ebx) # proc_sig->saved_hstate->execp->eflags
+
+ pushl $UCODE_SEG # cs
+ pushl psig_sigact(%eax) # %eip = proc_sig->sigact
+
+ movw $UDATA_SEG, %cx # switch data seg to user mode
+ movw %cx, %es
+ movw %cx, %ds
+ movw %cx, %fs
+ movw %cx, %gs
+
+ iret
\ No newline at end of file
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