#define __ASM__ #include #include #include #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 128 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 .global interrupt_wrapper interrupt_wrapper: /* Stack layout (layout of struct isr_param) msa: [ss] > 76 [esp] > 72 eflags > 68 cs > 64 eip > 60 err_code > 56 vector > offset = 52 [saved_prev_ctx] > offset = 0 --- esp gs fs es ds > offset = 7 * 4 = 28 + 4 esi ebp edi edx ecx ebx eax lsa: depth > offset = 0 las: Least Significant Address msa: Most Significant Address */ cld subl $52, %esp 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 movl __current, %eax movl 8(%eax), %eax incl %eax pushl %eax # nested intr: current depth movl 116(%esp), %eax /* 取出 %cs */ andl $0x3, %eax /* 判断 RPL */ jz 1f movw $KDATA_SEG, %ax /* 如果从用户模式转来，则切换至内核数据段 */ movw %ax, %gs movw %ax, %fs movw %ax, %ds movw %ax, %es # 保存用户栈顶指针。这是因为我们允许系统调用内进行上下文切换，而这样一来，我们就失去了用户栈的信息， # 这样一来，就无法设置信号上下文。这主要是为了实现了pause()而做的准备 movl __current, %eax # 保存x87FPU的状态 movl 68(%eax), %ebx fxsave (%ebx) movl 124(%esp), %ebx # 取出esp movl %ebx, 60(%eax) # 存入__current->ustack_top 1: movl %esp, %eax andl $0xfffffff0, %esp subl $16, %esp movl %eax, (%esp) call intr_handler movl (%esp), %eax .global soft_iret soft_iret: movl %eax, %esp #ifdef __ASM_INTR_DIAGNOSIS movl %eax, (debug_resv + 8) movl 48(%esp), %eax movl 60(%eax), %eax movl %eax, (debug_resv + 4) # eip #endif movl __current, %eax movl 68(%eax), %eax test %eax, %eax # do we have stored x87 context? jz 1f fxrstor (%eax) 1: popl %eax # discard isr_param::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, %eax # nested intr: restore saved context popl 8(%eax) # depth popl 12(%eax) # eax popl 16(%eax) # ebx popl 20(%eax) # ecx popl 24(%eax) # edx popl 28(%eax) # edi popl 32(%eax) # ebp popl 36(%eax) # esi popl 40(%eax) # ds popl 44(%eax) # es popl 48(%eax) # fs popl 52(%eax) # gs popl 56(%eax) # esp 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 + 4) movl tmp_store, %eax iret .global switch_to switch_to: # 约定 # arg1: 目标进程PCB地址 (next popl %ebx # next movl __current, %eax movl 64(%eax), %ecx # __current->pagetable movl 64(%ebx), %eax # next->pagetable cmpl %ecx, %eax # if(next->pagtable != __current->pagetable) { jz 1f movl %eax, %cr3 # cpu_lcr3(next->pagetable) # } 1: movl %ebx, __current # __current = next # 我们已经处在了新的地址空间，为了避免影响其先前的栈布局 # 需要使用一个临时的栈空间 movl $tmp_stack, %esp call signal_dispatch # kernel/signal.c test %eax, %eax # do we have signal to handle? jz 1f jmp handle_signal 1: leal 8(%ebx), %eax jmp soft_iret .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！ leal 8(%eax), %ebx # arg1 in %eax: addr of proc_sig structure in user stack pushl $UDATA_SEG # proc_sig->prev_context.proc_regs.ss pushl %eax # esp movl 48(%ebx), %ebx pushl 68(%ebx) # proc_sig->prev_context.proc_regs.execp->eflags pushl $UCODE_SEG # cs pushl $sig_wrapper # eip for sig wrapper movw $UDATA_SEG, %cx # switch data seg to user mode movw %cx, %es movw %cx, %ds movw %cx, %fs movw %cx, %gs iret .section .usrtext sig_wrapper: # in user mode movl %esp, %eax and $0xfffffff0, %esp subl $8, %esp pushl %eax # Addr to proc_sig structure pushl 4(%eax) # proc_sig->sig_num ---- 16 bytes aligned call *(%eax) # invoke signal handler # invoke the sigreturn syscall to exit the signal wrapper movl $__SYSCALL_sigreturn, %eax movl 4(%esp), %ebx int $LUNAIX_SYS_CALL ud2 # never reach!