docs/zh_CN: Add dev-tools/gdb-kernel-debugging.rst Chinese translation
Translate dev-tools/gdb-kernel-debugging.rst into Chinese. Signed-off-by: gaochao <gaochao49@huawei.com> Reviewed-by: Yanteng Si <siyanteng@loongson.cn> Reviewed-by: Wu XiangCheng <bobwxc@email.cn> Link: https://lore.kernel.org/r/20220514100046.1683-1-gaochao49@huawei.com Signed-off-by: Jonathan Corbet <corbet@lwn.net>
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Jonathan Corbet
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.. include:: ../disclaimer-zh_CN.rst
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:Original: Documentation/dev-tools/gdb-kernel-debugging.rst
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:Translator: 高超 gao chao <gaochao49@huawei.com>
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通过gdb调试内核和模块
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=====================
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Kgdb内核调试器、QEMU等虚拟机管理程序或基于JTAG的硬件接口，支持在运行时使用gdb
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调试Linux内核及其模块。Gdb提供了一个强大的python脚本接口，内核也提供了一套
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辅助脚本以简化典型的内核调试步骤。本文档为如何启用和使用这些脚本提供了一个简要的教程。
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此教程基于QEMU/KVM虚拟机，但文中示例也适用于其他gdb stub。
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环境配置要求
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------------
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- gdb 7.2+ (推荐版本: 7.4+) 且开启python支持 (通常发行版上都已支持)
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设置
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----
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- 创建一个QEMU/KVM的linux虚拟机（详情请参考 www.linux-kvm.org 和 www.qemu.org ）。
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对于交叉开发，https://landley.net/aboriginal/bin 提供了一些镜像和工具链，
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可以帮助搭建交叉开发环境。
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- 编译内核时开启CONFIG_GDB_SCRIPTS，关闭CONFIG_DEBUG_INFO_REDUCED。
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如果架构支持CONFIG_FRAME_POINTER，请保持开启。
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- 在guest环境上安装该内核。如有必要，通过在内核command line中添加“nokaslr”来关闭KASLR。
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此外，QEMU允许通过-kernel、-append、-initrd这些命令行选项直接启动内核。
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但这通常仅在不依赖内核模块时才有效。有关此模式的更多详细信息，请参阅QEMU文档。
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在这种情况下，如果架构支持KASLR，应该在禁用CONFIG_RANDOMIZE_BASE的情况下构建内核。
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- 启用QEMU/KVM的gdb stub，可以通过如下方式实现
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- 在VM启动时，通过在QEMU命令行中添加“-s”参数
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或
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- 在运行时通过从QEMU监视控制台发送“gdbserver”
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- 切换到/path/to/linux-build(内核源码编译)目录
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- 启动gdb：gdb vmlinux
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注意：某些发行版可能会将gdb脚本的自动加载限制在已知的安全目录中。
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如果gdb报告拒绝加载vmlinux-gdb.py（相关命令找不到），请将::
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add-auto-load-safe-path /path/to/linux-build
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添加到~/.gdbinit。更多详细信息，请参阅gdb帮助信息。
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- 连接到已启动的guest环境::
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(gdb) target remote :1234
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使用Linux提供的gdb脚本的示例
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----------------------------
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- 加载模块（以及主内核）符号::
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(gdb) lx-symbols
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loading vmlinux
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scanning for modules in /home/user/linux/build
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loading @0xffffffffa0020000: /home/user/linux/build/net/netfilter/xt_tcpudp.ko
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loading @0xffffffffa0016000: /home/user/linux/build/net/netfilter/xt_pkttype.ko
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loading @0xffffffffa0002000: /home/user/linux/build/net/netfilter/xt_limit.ko
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loading @0xffffffffa00ca000: /home/user/linux/build/net/packet/af_packet.ko
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loading @0xffffffffa003c000: /home/user/linux/build/fs/fuse/fuse.ko
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...
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loading @0xffffffffa0000000: /home/user/linux/build/drivers/ata/ata_generic.ko
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- 对一些尚未加载的模块中的函数函数设置断点，例如::
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(gdb) b btrfs_init_sysfs
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Function "btrfs_init_sysfs" not defined.
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Make breakpoint pending on future shared library load? (y or [n]) y
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Breakpoint 1 (btrfs_init_sysfs) pending.
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- 继续执行::
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(gdb) c
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- 加载模块并且能观察到正在加载的符号以及断点命中::
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loading @0xffffffffa0034000: /home/user/linux/build/lib/libcrc32c.ko
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loading @0xffffffffa0050000: /home/user/linux/build/lib/lzo/lzo_compress.ko
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loading @0xffffffffa006e000: /home/user/linux/build/lib/zlib_deflate/zlib_deflate.ko
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loading @0xffffffffa01b1000: /home/user/linux/build/fs/btrfs/btrfs.ko
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Breakpoint 1, btrfs_init_sysfs () at /home/user/linux/fs/btrfs/sysfs.c:36
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36 btrfs_kset = kset_create_and_add("btrfs", NULL, fs_kobj);
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- 查看内核的日志缓冲区::
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(gdb) lx-dmesg
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[ 0.000000] Initializing cgroup subsys cpuset
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[ 0.000000] Initializing cgroup subsys cpu
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[ 0.000000] Linux version 3.8.0-rc4-dbg+ (...
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[ 0.000000] Command line: root=/dev/sda2 resume=/dev/sda1 vga=0x314
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[ 0.000000] e820: BIOS-provided physical RAM map:
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[ 0.000000] BIOS-e820: [mem 0x0000000000000000-0x000000000009fbff] usable
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[ 0.000000] BIOS-e820: [mem 0x000000000009fc00-0x000000000009ffff] reserved
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....
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- 查看当前task struct结构体的字段（仅x86和arm64支持）::
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(gdb) p $lx_current().pid
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$1 = 4998
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(gdb) p $lx_current().comm
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$2 = "modprobe\000\000\000\000\000\000\000"
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- 对当前或指定的CPU使用per-cpu函数::
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(gdb) p $lx_per_cpu("runqueues").nr_running
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$3 = 1
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(gdb) p $lx_per_cpu("runqueues", 2).nr_running
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$4 = 0
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- 使用container_of查看更多hrtimers信息::
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(gdb) set $next = $lx_per_cpu("hrtimer_bases").clock_base[0].active.next
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(gdb) p *$container_of($next, "struct hrtimer", "node")
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$5 = {
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node = {
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node = {
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__rb_parent_color = 18446612133355256072,
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rb_right = 0x0 <irq_stack_union>,
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rb_left = 0x0 <irq_stack_union>
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},
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expires = {
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tv64 = 1835268000000
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}
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},
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_softexpires = {
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tv64 = 1835268000000
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},
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function = 0xffffffff81078232 <tick_sched_timer>,
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base = 0xffff88003fd0d6f0,
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state = 1,
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start_pid = 0,
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start_site = 0xffffffff81055c1f <hrtimer_start_range_ns+20>,
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start_comm = "swapper/2\000\000\000\000\000\000"
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}
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命令和辅助调试功能列表
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----------------------
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命令和辅助调试功能可能会随着时间的推移而改进，此文显示的是初始版本的部分示例::
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(gdb) apropos lx
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function lx_current -- Return current task
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function lx_module -- Find module by name and return the module variable
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function lx_per_cpu -- Return per-cpu variable
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function lx_task_by_pid -- Find Linux task by PID and return the task_struct variable
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function lx_thread_info -- Calculate Linux thread_info from task variable
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lx-dmesg -- Print Linux kernel log buffer
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lx-lsmod -- List currently loaded modules
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lx-symbols -- (Re-)load symbols of Linux kernel and currently loaded modules
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可以通过“help <command-name>”或“help function <function-name>”命令
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获取指定命令或指定调试功能的更多详细信息。
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@ -25,6 +25,7 @@ Documentation/translations/zh_CN/dev-tools/testing-overview.rst
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sparse
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gcov
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kasan
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gdb-kernel-debugging
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Todolist:
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@ -34,7 +35,6 @@ Todolist:
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- kmemleak
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- kcsan
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- kfence
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- gdb-kernel-debugging
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- kgdb
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- kselftest
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- kunit/index
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