在 2022/4/7 AM12:57, Richard Henderson 写道:
> On 4/6/22 09:30, Shuai Xue wrote:
>> Dear, folks,
>>
>> I try to debug Linux kernel with QEMU in single-stepping mode on aarch64
>> platform,
>> the added breakpoint hits but after I type `step`, the gdb always jumps into
>> interrupt.
>>
>> My env:
>>
>> gdb-10.2
>> qemu-6.2.0
>> host kernel: 5.10.84
>> VM kernel: 5.10.84
>>
>> The steps to reproduce:
>> # host console: run a VM with only one core, the import arg: <qemu:arg
>> value='-s'/>
>> # details can be found here:
>> https://www.redhat.com/en/blog/debugging-kernel-qemulibvirt
>> virsh create dev_core0.xml
>>
>> # run gdb client
>> gdb ./vmlinux
>>
>> # gdb client on host console
>> (gdb) dir
>> ./usr/src/debug/kernel-5.10.84/linux-5.10.84-004.alpha.ali5000.alios7.aarch64
>> (gdb) target remote localhost:1234
>> (gdb) info b
>> Num Type Disp Enb Address What
>> 1 breakpoint keep y <MULTIPLE>
>> 1.1 y 0xffff800010361444
>> mm/memory-failure.c:1318
>> 1.2 y 0xffff800010361450 in memory_failure
>> at
>> mm/memory-failure.c:1488
>> (gdb) c
>> Continuing.
>>
>> # console in VM, use madvise to inject a hwposion at virtual address
>> vaddr,
>> # which will hit the b inmemory_failur: madvise(vaddr, pagesize,
>> MADV_HWPOISON);
>> # and the VM pause
>> ./run_madvise.c
>>
>> # gdb client on host console
>> (gdb)
>> Continuing.
>> Breakpoint 1, 0xffff800010361444 in memory_failure () at
>> mm/memory-failure.c:1318
>> 1318 res = -EHWPOISON;
>> (gdb) n
>> vectors () at arch/arm64/kernel/entry.S:552
>> 552 kernel_ventry 1, irq // IRQ
>> EL1h
>
> The 'n' command is not a single-step: use stepi, which will suppress
> interrupts.
> Anyway, not a bug.
>
> r~
Hi, Richard,
Thank you for your quick reply, I also try `stepi`, but it does NOT work either.
(gdb) c
Continuing.
Breakpoint 1, memory_failure (pfn=1273982, flags=1) at
mm/memory-failure.c:1488
1488 {
(gdb) stepi
vectors () at arch/arm64/kernel/entry.S:552
552 kernel_ventry 1, irq // IRQ
EL1h
According to QEMU doc[1]: the default single stepping behavior is step with the
IRQs
and timer service routines off. I checked the MASK bits used to control the
single
stepping IE on my machine as bellow:
# gdb client on host (x86 plafrom)
(gdb) maintenance packet qqemu.sstepbits
sending: "qqemu.sstepbits"
received: "ENABLE=1,NOIRQ=2,NOTIMER=4"
The sstep MASK looks as expected, but does not work as expected.
I also try the same kernel and qemu version on X86 platform:
>> gdb-10.2
>> qemu-6.2.0
>> host kernel: 5.10.84
>> VM kernel: 5.10.84
The command `n` jumps to the next instruction.
# gdb client on host (x86 plafrom)
(gdb) b memory-failure.c:1488
Breakpoint 1, memory_failure (pfn=1128931, flags=1) at
mm/memory-failure.c:1488
1488 {
(gdb) n
1497 if (!sysctl_memory_failure_recovery)
(gdb) stepi
0xffffffff812efdbc 1497 if
(!sysctl_memory_failure_recovery)
(gdb) stepi
0xffffffff812efdbe 1497 if
(!sysctl_memory_failure_recovery)
(gdb) n
1500 p = pfn_to_online_page(pfn);
(gdb) l
1496
1497 if (!sysctl_memory_failure_recovery)
1498 panic("Memory failure on page %lx", pfn);
1499
1500 p = pfn_to_online_page(pfn);
1501 if (!p) {
Best Regrades,
Shuai
[1] https://github.com/qemu/qemu/blob/master/docs/system/gdb.rst
