修改Linux内核编译选项
- 参考
- 注意 这个选项可能找不到
- 还需要修改
menuconfig中的一个设置
- 关闭下面这一条，否则也无法实现在规定的断点位置停下
进入内核
- 使用qemu执行如下命令
qemu-system-x86_64 -s -S \
-netdev "user,id=eth0" \
-device "e1000,netdev=eth0" \
-object "filter-dump,id=eth0,netdev=eth0,file=dump.dat" \
-kernel $kernel_image \
-append "root=/dev/am rdinit=sbin/init ip=10.0.2.15::10.0.2.1:255.255.255.0 console=ttyS0" \
-nographic \
-initrd $rootfs_img -s参数表示在1234端口接受GDB调试，-S参数表示冻结CPU直到远程GDB输入相应命令- 然后输入
gdb vmlinux target remote localhost:1234- 然后
- 然后输入
continue或c继续执行gdb的使用
b <函数名>在函数位置设置断点
- 使用
step单步执行 info locals显示当前环境的局部变量info args显示函数的传入参数等等- 有时候一些变量会因为编译过程中被优化掉了导致无法查看，显示为
<optimized out> - 可以通过设置为
volatile或者防止优化改变上述状况一些内核调试经验
warning trace
- 如下的trace
[ 111.555855] ------------[ cut here ]------------
[ 111.560683] WARNING: CPU: 0 PID: 129 at kernel/dma/mapping.c:533 dma_free_attrs+0x4a/0x60
[ 111.562335] Modules linked in: r4l_e1000_demo(OE)
[ 111.563461] CPU: 0 PID: 129 Comm: ip Tainted: G W OE 6.1.0-rc1 #38
[ 111.564123] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
[ 111.564595] RIP: 0010:dma_free_attrs+0x4a/0x60
[ 111.565445] Code: 40 00 a9 00 02 00 00 74 21 48 85 d2 74 13 4d 85 c9 74 10 4d 8b 59 10 4d 85 db 74 05 e8 ef c0
[ 111.566470] RSP: 0018:ffffc90000673a80 EFLAGS: 00000046
[ 111.567058] RAX: 0000000000000046 RBX: ffff88800425a0d0 RCX: 000000000608b000
[ 111.567506] RDX: ffff88800608b000 RSI: 0000000000000080 RDI: ffff88800425a0d0
[ 111.568004] RBP: ffffc90000673a80 R08: 0000000000000000 R09: 0000000000000000
[ 111.568556] R10: ffffffff82ab6ff0 R11: ffffffff818fa860 R12: 0000000000000080
[ 111.569160] R13: 0000000000000041 R14: 000000000608b000 R15: ffff88800608b000
[ 111.569613] FS: 00000000024fa3c0(0000) GS:ffff888007600000(0000) knlGS:0000000000000000
[ 111.570234] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 111.570839] CR2: 00000000005305a1 CR3: 0000000006068000 CR4: 00000000000006f0
[ 111.571537] Call Trace:
[ 111.572137] <TASK>
[ 111.573023] rust_helper_dma_free_coherent+0x3c/0x50
[ 111.573691] _RINvNtCs3yuwAp0waWO_4core3ptr13drop_in_placeINtNtCsa5tTp5JGY9w_14r4l_e1000_demo8ring_buf7RingBu]
[ 111.574911] ? _RNvXs4_NtNtNtCs3yuwAp0waWO_4core3fmt3num3impxNtB9_7Display3fmt+0x30/0x30
[ 111.576226] _RNvXs7_Csa5tTp5JGY9w_14r4l_e1000_demoNtB5_9NetDeviceNtNtCsfATHBUcknU9_6kernel3net16DeviceOperat]
[ 111.577870] _RNvMs2_NtCsfATHBUcknU9_6kernel3netINtB5_12RegistrationNtCsa5tTp5JGY9w_14r4l_e1000_demo9NetDevic]
[ 111.579888] __dev_close_many+0x124/0x170
[ 111.580119] __dev_change_flags+0xf5/0x200
[ 111.580311] dev_change_flags+0x27/0x60
[ 111.580567] devinet_ioctl+0x4ec/0x600
[ 111.580943] inet_ioctl+0xec/0x1a0
[ 111.581246] ? _copy_to_user+0x1d/0x30
[ 111.581408] ? put_user_ifreq+0x49/0x60
[ 111.581569] ? sock_do_ioctl+0xae/0x100
[ 111.581925] sock_do_ioctl+0x3e/0x100
[ 111.582206] sock_ioctl+0x2ac/0x360
[ 111.582796] __se_sys_ioctl+0x7c/0xc0
[ 111.583239] __x64_sys_ioctl+0x1d/0x20
[ 111.583579] do_syscall_64+0x62/0x90
[ 111.583833] ? do_user_addr_fault+0x3b5/0x4f0
[ 111.584116] ? exit_to_user_mode_prepare+0x3c/0xa0
[ 111.584622] ? irqentry_exit_to_user_mode+0x9/0x20
[ 111.585147] ? irqentry_exit+0x12/0x40
[ 111.585467] ? exc_page_fault+0x8e/0x210
[ 111.585871] entry_SYSCALL_64_after_hwframe+0x63/0xcd
[ 111.586505] RIP: 0033:0x4afa6f
[ 111.587134] Code: 00 48 89 44 24 18 31 c0 48 8d 44 24 60 c7 04 24 10 00 00 00 48 89 44 24 08 48 8d 44 24 20 40
[ 111.588324] RSP: 002b:00007ffe25bed850 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
[ 111.589367] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00000000004afa6f
[ 111.589720] RDX: 00007ffe25bed910 RSI: 0000000000008914 RDI: 0000000000000003
[ 111.589961] RBP: 0000000000640287 R08: 0000000000000000 R09: 0000000000000000
[ 111.590853] R10: 00007ffe25beef40 R11: 0000000000000246 R12: 0000000000000003
[ 111.591466] R13: 00007ffe25bed910 R14: 0000000000000000 R15: 0000000000000000
[ 111.592168] </TASK>
[ 111.592524] ---[ end trace 0000000000000000 ]--- - 是Warning Trace，并不是内核出现错误，出现段错误一般会有
segmentation fault或者core dumped - 这个仅仅是警告
- 触发原因是内核
dma_free_attrs函数有一个语句WARN_ON(irqs_disabled()) todo
