无法让 gdb 在 Qemu 下的 Linux 内核 运行 中的断点处停止
Can't get gdb to stop at breakpoint in Linux kernel running under Qemu
已编译 linux 5.5.5 内核，使用 make menuconfig 添加选项 CONFIG_GDB_SCRIPTS 并关闭选项 CONFIG_DEBUG_INFO_REDUCED 。
运行 qemu
qemu-system-x86_64 \
-kernel arch/x86/boot/bzImage \
-append "root=/dev/sda1" \
-device virtio-scsi-pci,id=scsi0 \
-drive file=../../zso2020_cow.qcow2,if=none,id=drive0 \
-device scsi-hd,bus=scsi0.0,drive=drive0 \
-enable-kvm \
-smp 1 \
-net nic,model=virtio -net user \
-net user,hostfwd=tcp::2222-:22 \
-m 1G -balloon virtio \
-fsdev local,id=hshare,path=$(pwd),security_model=none -device virtio-9p-pci,fsdev=hshare,mount_tag=hshare \
-chardev stdio,id=cons,signal=off -device virtio-serial-pci -device virtconsole,chardev=cons \
-soundhw hda \
-usb -device usb-mouse \
-gdb tcp::23308 \
-display none \
-S
Qemu 使用编译内核运行，我在源代码中使用 kprint 检查过。
然后我跑了
gdb \
-ex "add-auto-load-safe-path $(pwd)" \
-ex "file vmlinux" \
-ex 'target remote localhost:23308' \
-ex 'break start_kernel' \
-ex 'continue'
（两个脚本都是从编译内核的目录运行的）
Qemu进入用户登录，gdb输出（等待断点）
GNU gdb (Ubuntu 8.1-0ubuntu3.2) 8.1.0.20180409-git
Copyright (C) 2018 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law. Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
<http://www.gnu.org/software/gdb/documentation/>.
For help, type "help".
Type "apropos word" to search for commands related to "word".
Reading symbols from vmlinux...done.
Remote debugging using localhost:23308
0x000000000000fff0 in exception_stacks ()
Breakpoint 1 at 0xffffffff8271db30: file init/main.c, line 577.
Continuing.
我也试过了
hbr 代替 br
先target remote :23308 i 设置断点，然后file vmlinux
进入编译好的内核目录，从qemu级别安装内核
在任何情况下，gdb 都不会在断点处停止。
如何使用 gdb 正确连接到内核，在哪里查找错误？
问题的解决方案是添加 nokaslr 选项并使用 hbreak。这意味着替换
-append "root=/dev/sda1"
和
`-附加 "root=/dev/sda1 nokaslr"
和
break start_kernel
和
hbreak start_kernel
然后 gdb 正确捕获内核断点。
已编译 linux 5.5.5 内核，使用 make menuconfig 添加选项 CONFIG_GDB_SCRIPTS 并关闭选项 CONFIG_DEBUG_INFO_REDUCED 。 运行 qemu
qemu-system-x86_64 \
-kernel arch/x86/boot/bzImage \
-append "root=/dev/sda1" \
-device virtio-scsi-pci,id=scsi0 \
-drive file=../../zso2020_cow.qcow2,if=none,id=drive0 \
-device scsi-hd,bus=scsi0.0,drive=drive0 \
-enable-kvm \
-smp 1 \
-net nic,model=virtio -net user \
-net user,hostfwd=tcp::2222-:22 \
-m 1G -balloon virtio \
-fsdev local,id=hshare,path=$(pwd),security_model=none -device virtio-9p-pci,fsdev=hshare,mount_tag=hshare \
-chardev stdio,id=cons,signal=off -device virtio-serial-pci -device virtconsole,chardev=cons \
-soundhw hda \
-usb -device usb-mouse \
-gdb tcp::23308 \
-display none \
-S
Qemu 使用编译内核运行，我在源代码中使用 kprint 检查过。 然后我跑了
gdb \
-ex "add-auto-load-safe-path $(pwd)" \
-ex "file vmlinux" \
-ex 'target remote localhost:23308' \
-ex 'break start_kernel' \
-ex 'continue'
（两个脚本都是从编译内核的目录运行的）
Qemu进入用户登录，gdb输出（等待断点）
GNU gdb (Ubuntu 8.1-0ubuntu3.2) 8.1.0.20180409-git
Copyright (C) 2018 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law. Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
<http://www.gnu.org/software/gdb/documentation/>.
For help, type "help".
Type "apropos word" to search for commands related to "word".
Reading symbols from vmlinux...done.
Remote debugging using localhost:23308
0x000000000000fff0 in exception_stacks ()
Breakpoint 1 at 0xffffffff8271db30: file init/main.c, line 577.
Continuing.
我也试过了
hbr代替br先
target remote :23308i 设置断点，然后file vmlinux进入编译好的内核目录，从qemu级别安装内核
在任何情况下，gdb 都不会在断点处停止。
如何使用 gdb 正确连接到内核，在哪里查找错误？
问题的解决方案是添加 nokaslr 选项并使用 hbreak。这意味着替换
-append "root=/dev/sda1"
和
`-附加 "root=/dev/sda1 nokaslr"
和
break start_kernel
和
hbreak start_kernel
然后 gdb 正确捕获内核断点。