Assembly iretq投掷总成故障
我正在尝试编写一个64位操作系统。它从计时器中断处理程序在iretq上抛出一个GP,然后从GP处理程序的iretq重复抛出更多的GPs 我知道这一点,因为我的通用处理程序在串行端口上打印ISR号,它是32,13,13,13 GP的错误代码是10,这是我的数据段 我正在qemu中调试它,所以我可以看到很多。以下是来自计时器处理程序的iretq的情况:Assembly iretq投掷总成故障,assembly,operating-system,kernel,x86-64,interrupt-handling,Assembly,Operating System,Kernel,X86 64,Interrupt Handling,我正在尝试编写一个64位操作系统。它从计时器中断处理程序在iretq上抛出一个GP,然后从GP处理程序的iretq重复抛出更多的GPs 我知道这一点,因为我的通用处理程序在串行端口上打印ISR号,它是32,13,13,13 GP的错误代码是10,这是我的数据段 我正在qemu中调试它,所以我可以看到很多。以下是来自计时器处理程序的iretq的情况: (gdb) disas isr_common,isr_head_2
(gdb) disas isr_common,isr_head_2
Dump of assembler code from 0x8189 to 0x81c4:
0x0000000000008189 <isr_common+0>: callq 0x8125 <sayN100>
0x000000000000818e <isr_common+5>: cmp $0x20,%eax
0x0000000000008191 <isr_common+8>: jl 0x81a8 <isr_common.no_more_acks>
0x0000000000008193 <isr_common+10>: cmp $0x30,%eax
0x0000000000008196 <isr_common+13>: jge 0x81a8 <isr_common.no_more_acks>
0x0000000000008198 <isr_common+15>: cmp $0x28,%al
0x000000000000819a <isr_common+17>: jl 0x81a2 <isr_common.ack_master>
0x000000000000819c <isr_common+19>: push %rax
0x000000000000819d <isr_common+20>: mov $0x20,%al
0x000000000000819f <isr_common+22>: out %al,$0xa0
0x00000000000081a1 <isr_common+24>: pop %rax
0x00000000000081a2 <isr_common.ack_master+0>: push %rax
0x00000000000081a3 <isr_common.ack_master+1>: mov $0x20,%al
0x00000000000081a5 <isr_common.ack_master+3>: out %al,$0x20
0x00000000000081a7 <isr_common.ack_master+5>: pop %rax
0x00000000000081a8 <isr_common.no_more_acks+0>: cmp $0x24,%ax
0x00000000000081ac <isr_common.no_more_acks+4>: pop %rax
0x00000000000081ad <isr_common.no_more_acks+5>: pop %rax
=> 0x00000000000081ae <isr_common.end+0>: iretq
0x00000000000081b0 <isr_head_0+0>: pushq $0x55 ;DUMMY ERROR CODE
0x00000000000081b2 <isr_head_0+2>: mov $0x0,%eax
0x00000000000081b7 <isr_head_0+7>: push %rax
0x00000000000081b8 <isr_head_0+8>: jmp 0x8189 <isr_common>
0x00000000000081ba <isr_head_1+0>: pushq $0x55 ;DUMMY ERROR CODE
0x00000000000081bc <isr_head_1+2>: mov $0x1,%eax
0x00000000000081c1 <isr_head_1+7>: push %rax
0x00000000000081c2 <isr_head_1+8>: jmp 0x8189 <isr_common>
其中:
0x0000000000008122 <LongMode.Nirv+0>: hlt
0x0000000000008123 <LongMode.Nirv+1>: jmp 0x8122 <LongMode.Nirv>
我们看到,它将错误代码0x10推到通常的带有选择器的堆栈、带有选择器的标志和返回地址之后,但有趣的是,我的计时器(0x55)中的虚拟错误代码又死而复生了。
我们已经知道它是由第一个iretq弹出的,这次我没有推它:
(gdb) disas isr_head_13
Dump of assembler code for function isr_head_13:
=> 0x0000000000008236 <+0>: mov $0xd,%eax
0x000000000000823b <+5>: push %rax
0x000000000000823c <+6>: jmpq 0x8189 <isr_common>
(gdb)disas isr头13
函数isr\u head\u 13的汇编程序代码转储:
=>0x0000000000008236:mov$0xd,%eax
0x000000000000823b:推送%rax
0x000000000000823c:jmpq 0x8189
我想这只是16字节的对齐方式,但我并没有真正参与其中。在计时器关闭之前,堆栈是16字节对齐的,但是CPU推了奇数个longlong
那它为什么会崩溃呢?英特尔文档说,GP带有选择器意味着它试图弹出超出范围的内容,但我看不出有这样的问题
非常感谢您的帮助。在第一次IRET时,堆栈上的CS选择器是10,这是一个数据段,因此这就是导致#GP的原因。要么堆栈在处理程序中被修改(看起来不是这样),要么CS寄存器在更改GDT后没有被重新加载 来自GP处理程序的IRET返回到上一个IRET,该IRET会立即再次出现故障。除非已解决故障,否则通常不应从故障处理程序返回
它看起来不像是保存和恢复处理程序中的所有寄存器,一旦IRET开始工作,这将导致问题。我注意到的一件事是RAX没有正确恢复。在堆栈上推送一个潜在的错误代码,用一个中断号击打RAX,在堆栈上推送它,然后在IRETQ之前执行两次POP%RAX。这意味着,当中断结束时,RAX将接受虚拟错误代码,而不是它在进入handler.Ooh时可能具有的值。这听起来像是解释。我回家后会看看为什么CS从来没有像应该的那样8岁。是的。就这样。我刚刚将早期的jmp LongMode更改为jmp 8:LongMode,现在一切正常。谢谢
(gdb) info registers
rax 0x55 85
rbx 0x80000011 2147483665
rcx 0xc0000080 3221225600
rdx 0x3f8 1016
rsi 0xb 11
rdi 0x3fc 1020
rbp 0x0 0x0
rsp 0x14fd8 0x14fd8 <Pd+36824>
r8 0x0 0
r9 0x0 0
r10 0x0 0
r11 0x0 0
r12 0x0 0
r13 0x0 0
r14 0x0 0
r15 0x0 0
rip 0x81ae 0x81ae <isr_common.end>
eflags 0x97 [ CF PF AF SF ]
cs 0x8 8
ss 0x10 16
ds 0x10 16
es 0x10 16
fs 0x10 16
gs 0x10 16
(gdb) x/32xg 0x14f00
0x14f00 <Pd+36608>: 0x0000000000841f0f 0x000000841f0f2e66
0x14f10 <Pd+36624>: 0x00841f0f2e660000 0x1f0f2e6600000000
0x14f20 <Pd+36640>: 0x2e66000000000084 0x0000000000841f0f
0x14f30 <Pd+36656>: 0x000000841f0f2e66 0x00841f0f2e660000
0x14f40 <Pd+36672>: 0x1f0f2e6600000000 0x2e66000000000084
0x14f50 <Pd+36688>: 0x0000000000841f0f 0x000000841f0f2e66
0x14f60 <Pd+36704>: 0x00841f0f2e660000 0x1f0f2e6600000000
0x14f70 <Pd+36720>: 0x2e66000000000084 0x0000000000841f0f
0x14f80 <Pd+36736>: 0x000000841f0f2e66 0x00841f0f2e660000
0x14f90 <Pd+36752>: 0x1f0f2e6600000000 0x2e66000000000084
0x14fa0 <Pd+36768>: 0x0000000000000020 0x0000000000008144
0x14fb0 <Pd+36784>: 0x0000000080000011 0x0000000000000020
0x14fc0 <Pd+36800>: 0x0000000000000020 0x0000000000000020
0x14fd0 <Pd+36816>: 0x0000000000000055 0x0000000000008123
0x14fe0 <Pd+36832>: 0x0000000000000010 0x0000000000000216
0x14ff0 <Pd+36848>: 0x0000000000015000 0x0000000000000010
(gdb) break isr_head_13
Breakpoint 3 at 0x8236
(gdb) c
Continuing.
Breakpoint 3, 0x0000000000008236 in isr_head_13 ()
(gdb) bt
#0 0x0000000000008236 in isr_head_13 ()
#1 0x0000000000000010 in ?? ()
#2 0x00000000000081ae in isr_common.no_more_acks ()
#3 0x0000000000000008 in ?? ()
#4 0x0000000000000097 in ?? ()
#5 0x0000000000014fd8 in Pd ()
#6 0x0000000000000010 in ?? ()
#7 0x0000000000000055 in ?? ()
#8 0x0000000000008123 in LongMode.Nirv ()
#9 0x0000000000000010 in ?? ()
#10 0x0000000000000216 in ?? ()
#11 0x0000000000015000 in Pd ()
#12 0x0000000000000010 in ?? ()
(gdb) disas isr_head_13
Dump of assembler code for function isr_head_13:
=> 0x0000000000008236 <+0>: mov $0xd,%eax
0x000000000000823b <+5>: push %rax
0x000000000000823c <+6>: jmpq 0x8189 <isr_common>