【kernel学习】内核下载与编译

内核下载与编译文章目录内核下载与编译1.内核下载2.验证kernel签名3.编译选项配置总结1.内核下载可以直接在官网下载：https://www.kernel.org~/Desktop/kernel_pwn_environment$ curl -O -L <https://mirrors.tuna.tsinghua.edu.cn/kernel/v5.x/linux-5.4.98.tar.x

Leee333

4682人浏览 · 2022-05-14 17:12:27

Leee333 · 2022-05-14 17:12:27 发布

内核下载与编译

文章目录

内核下载与编译
- 总结

1.内核下载

可以直接在官网下载：https://www.kernel.org

~/Desktop/kernel_pwn_environment$ curl -O -L <https://mirrors.tuna.tsinghua.edu.cn/kernel/v5.x/linux-5.4.98.tar.xz>
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100  104M  100  104M    0     0   376k      0  0:04:42  0:04:42 --:--:--  333k

下载完后直接解压：

~# unxz linux-5.4.98.tar.xz

2.验证kernel签名

内核签名的作用：

为了防止内核被恶意修改，在发布内核时，发布者会对内核进行签名。这里我们也对内核的签名进行校验。

rencvn@ubuntu:~/Desktop/kernel_pwn_environment$ curl -O -L <https://mirrors.tuna.tsinghua.edu.cn/kernel/v5.x/linux-5.4.98.tar.sign>
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   989  100   989    0     0   2491      0 --:--:-- --:--:-- --:--:--  2491
rencvn@ubuntu:~/Desktop/kernel_pwn_environment$ gpg --verify linux-5.4.98.tar.sign
gpg: assuming signed data in 'linux-5.4.98.tar'
gpg: Signature made Sat 13 Feb 2021 04:54:47 AM PST
gpg:                using RSA key 647F28654894E3BD457199BE38DBBDC86092693E
gpg: Can't check signature: No public key

同样也是遇到了ctfwiki上出现的问题，“can’t check signature: No public key”

这主要是因为我们没有相应的公钥来验证签名。此时我们可以下载相应内核版本发布者的公钥

我在下载公钥时报错，猜测应该是网速的问题，换成热点后直接下载下来了：

rencvn@ubuntu:~/Desktop/kernel_pwn_environment$ gpg --locate-keys torvalds@kernel.org gregkh@kernel.org
gpg: error retrieving 'gregkh@kernel.org' via WKD: Server indicated a failure
gpg: error reading key: Server indicated a failure
gpg: error retrieving 'torvalds@kernel.org' via WKD: Server indicated a failure
gpg: error reading key: Server indicated a failure
rencvn@ubuntu:~/Desktop/kernel_pwn_environment$ gpg --locate-keys torvalds@kernel.org gregkh@kernel.org
gpg: key 38DBBDC86092693E: public key "Greg Kroah-Hartman <gregkh@kernel.org>" imported
gpg: Total number processed: 1
gpg:               imported: 1
gpg: key 79BE3E4300411886: public key "Linus Torvalds <torvalds@kernel.org>" imported
gpg: Total number processed: 1
gpg:               imported: 1
pub   rsa4096 2011-09-23 [SC]
      647F28654894E3BD457199BE38DBBDC86092693E
uid           [ unknown] Greg Kroah-Hartman <gregkh@kernel.org>
sub   rsa4096 2011-09-23 [E]

pub   rsa2048 2011-09-20 [SC]
      ABAF11C65A2970B130ABE3C479BE3E4300411886
uid           [ unknown] Linus Torvalds <torvalds@kernel.org>
sub   rsa2048 2011-09-20 [E]

为了方便，我们也导入了 torvalds 的公钥。下面验证内核的签名

rencvn@ubuntu:~/Desktop/kernel_pwn_environment$ gpg --verify linux-5.4.98.tar.sign
gpg: assuming signed data in 'linux-5.4.98.tar'
gpg: Signature made Sat 13 Feb 2021 04:54:47 AM PST
gpg:                using RSA key 647F28654894E3BD457199BE38DBBDC86092693E
gpg: Good signature from "Greg Kroah-Hartman <gregkh@kernel.org>" [unknown]
gpg: WARNING: This key is not certified with a trusted signature!
gpg:          There is no indication that the signature belongs to the owner.
Primary key fingerprint: 647F 2865 4894 E3BD 4571  99BE 38DB BDC8 6092 693E

这里报了一个 WARNING。为了消除这个问题，我们可以选择使用 TOFU 信任对应的密钥

警告这里显示：公钥没有被信任的签名认证

rencvn@ubuntu:~/Desktop/kernel_pwn_environment$ gpg --tofu-policy good 647F28654894E3BD457199BE38DBBDC86092693E
gpg: Setting TOFU trust policy for new binding <key: 647F28654894E3BD457199BE38DBBDC86092693E, user id: Greg Kroah-Hartman <gregkh@kernel.org>> to good.
rencvn@ubuntu:~/Desktop/kernel_pwn_environment$ gpg --trust-model tofu --verify linux-5.4.98.tar.sign
gpg: assuming signed data in 'linux-5.4.98.tar'
gpg: Signature made Sat 13 Feb 2021 04:54:47 AM PST
gpg:                using RSA key 647F28654894E3BD457199BE38DBBDC86092693E
gpg: checking the trustdb
gpg: no ultimately trusted keys found
gpg: Good signature from "Greg Kroah-Hartman <gregkh@kernel.org>" [full]
gpg: gregkh@kernel.org: Verified 1 signature in the past 0 seconds.  Encrypted
     0 messages.

信任过后没有再报错，已验证成功.

在验证成功后，我们就可以解压缩压缩包得到内核源码。

tar -xf linux-5.4.98.tar

3.编译选项配置

在正式编译之前，我们可以配置内核的编译选项。

通过 make menuconfig来配置，但我输入后直接报错，上网查阅资料后，得知缺少了libncurses-dev库，flex,bison,安装后即可：

sudo apt-get install libncurses5-dev
apt-get install flex
apt-get install bison

安装后再次输入make menuconfig，

这里我们主要关注调试方面的选项，依次进入到 Kernel hacking -> Compile-time checks and compiler options，然后勾选如下选项Compile the kernel with debug info，以便于调试。不过似乎现在是默认开启的，如果要使用 kgdb 调试内核，则需要选中 KGDB: kernel debugger，并选中 KGDB 下的所有选项.

接着开始正式编译内核：

~# make -j3 bzImage

我输入后直接报错，好家伙，

rencvn@ubuntu:~/Desktop/kernel_pwn_environment/linux-5.4.98$ make -j3 bzImage
Makefile:632: include/config/auto.conf: No such file or directory
Makefile:678: include/config/auto.conf.cmd: No such file or directory
  HOSTLD  scripts/kconfig/conf
scripts/kconfig/conf  --syncconfig Kconfig
  SYSTBL  arch/x86/include/generated/asm/syscalls_32.h
  WRAP    arch/x86/include/generated/uapi/asm/bpf_perf_event.h
  WRAP    arch/x86/include/generated/uapi/asm/errno.h
  WRAP    arch/x86/include/generated/uapi/asm/fcntl.h
  WRAP    arch/x86/include/generated/uapi/asm/ioctl.h
  WRAP    arch/x86/include/generated/uapi/asm/ioctls.h
  WRAP    arch/x86/include/generated/uapi/asm/ipcbuf.h
  WRAP    arch/x86/include/generated/uapi/asm/param.h
  WRAP    arch/x86/include/generated/uapi/asm/poll.h
  WRAP    arch/x86/include/generated/uapi/asm/resource.h
  WRAP    arch/x86/include/generated/uapi/asm/socket.h
  WRAP    arch/x86/include/generated/uapi/asm/sockios.h
  WRAP    arch/x86/include/generated/uapi/asm/termbits.h
  WRAP    arch/x86/include/generated/uapi/asm/termios.h
  WRAP    arch/x86/include/generated/uapi/asm/types.h
  UPD     include/generated/uapi/linux/version.h
  UPD     include/config/kernel.release
  HOSTCC  arch/x86/tools/relocs_32.o
  WRAP    arch/x86/include/generated/asm/dma-contiguous.h
  WRAP    arch/x86/include/generated/asm/early_ioremap.h
  WRAP    arch/x86/include/generated/asm/export.h
  WRAP    arch/x86/include/generated/asm/mcs_spinlock.h
  WRAP    arch/x86/include/generated/asm/mm-arch-hooks.h
  WRAP    arch/x86/include/generated/asm/mmiowb.h
  UPD     include/generated/utsrelease.h
warning: Cannot use CONFIG_STACK_VALIDATION=y, please install libelf-dev, libelf-devel or elfutils-libelf-devel
  HOSTCC  scripts/genksyms/genksyms.o
  HOSTCC  arch/x86/tools/relocs_64.o
  YACC    scripts/genksyms/parse.tab.[ch]
  HOSTCC  arch/x86/tools/relocs_common.o
  LEX     scripts/genksyms/lex.lex.c
  HOSTCC  scripts/genksyms/parse.tab.o
  HOSTLD  arch/x86/tools/relocs
  HOSTCC  scripts/genksyms/lex.lex.o
  SYSHDR  arch/x86/include/generated/asm/unistd_32_ia32.h
  SYSHDR  arch/x86/include/generated/asm/unistd_64_x32.h
  SYSTBL  arch/x86/include/generated/asm/syscalls_64.h
  HOSTLD  scripts/genksyms/genksyms
  HOSTCC  scripts/selinux/genheaders/genheaders
  HOSTCC  scripts/selinux/mdp/mdp
  HOSTCC  scripts/bin2c
  HOSTCC  scripts/kallsyms
  HYPERCALLS arch/x86/include/generated/asm/xen-hypercalls.h
  HOSTCC  scripts/conmakehash
  SYSHDR  arch/x86/include/generated/uapi/asm/unistd_32.h
  SYSHDR  arch/x86/include/generated/uapi/asm/unistd_64.h
  SYSHDR  arch/x86/include/generated/uapi/asm/unistd_x32.h
  HOSTCC  scripts/recordmcount
  HOSTCC  scripts/sortextable
  HOSTCC  scripts/asn1_compiler
  HOSTCC  scripts/sign-file
scripts/sign-file.c:25:10: fatal error: openssl/opensslv.h: No such file or directory
 #include <openssl/opensslv.h>
          ^~~~~~~~~~~~~~~~~~~~
compilation terminated.
scripts/Makefile.host:107: recipe for target 'scripts/sign-file' failed
make[1]: *** [scripts/sign-file] Error 1
make[1]: *** Waiting for unfinished jobs....
Makefile:1120: recipe for target 'scripts' failed
make: *** [scripts] Error 2

根据这行提示：

warning: Cannot use CONFIG_STACK_VALIDATION=y, please install libelf-dev, libelf-devel or elfutils-libelf-devel

#### 解决1：

安装libelf-dev库：

~# sudo apt install libelf-dev

#### 解决2

安装好后执行make -j3 bzImage再次尝试编译，但还是报错：

scripts/extract-cert.c:21:10: fatal error: openssl/bio.h: No such file or directory

上网查看解决办法：

知道了出现scripts/extract-cert.c:21:25: fatal error: openssl /bio.h: No such file or directory 是因为没有安装libssl-dev或者已安装的libssl1.0.0版本太高, 无法支持

继续安装：

sudo apt install libssl-dev

安装好后，编译内核：

~#  make -j3 bzlmage

最后验证是否编译成功：

rencvn@ubuntu:~/Desktop/kernel_pwn_environment/linux-5.4.98$ uname -a
Linux ubuntu 5.4.0-109-generic #123~18.04.1-Ubuntu SMP Fri Apr 8 09:48:52 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux

感觉像是成功了，但跟着ctfwiki的接下来的目录，没找到bzlmage，离谱！！

#### 3.再次解决报错：

报错：

No rule to make target ‘debian/canonical-certs.pem‘, needed by ‘certs/x509_certificate_list

网上查到：

编辑.config文件(刚才在终端中执行过配置内核的命令#make menuconfig 后

会在该目录下生成一个隐藏文件.config)

~# vim .config

修改CONFIG_SYSTEM_TRUSTED_KEYS，将其赋空值

修改前：

CONFIG_SYSTEM_TRUSTED_KEYS="debian/canonical-certs.pem"

修改后：

CONFIG_SYSTEM_TRUSTED_KEYS=""

再次在终端输入：

~# make -j3 bzlmage

键入回车，看到在正常进行编译，终于成功!!

#### 4.高兴太早了，又出现报错

BTF: .tmp_vmlinux.btf: pahole (pahole) is not available
Failed to generate BTF for vmlinux
Try to disable CONFIG_DEBUG_INFO_BTF
Makefile:1100: recipe for target 'vmlinux' failed
make: *** [vmlinux] Error 1

一般是系统缺少dwarves软件包导致。

rencvn@ubuntu:~/Desktop/kernel_pwn_environment/linux-5.4.98$ sudo apt-get install dwarves

安装即可，继续执行：

~# make -j3 bzlmage

希望不要再出报错。

rencvn@ubuntu:~/Desktop/kernel_pwn_environment/linux-5.4.98$ make -j3 bzImage
  DESCEND  objtool
  CALL    scripts/atomic/check-atomics.sh
  CALL    scripts/checksyscalls.sh
  CHK     include/generated/compile.h
  GEN     .version
  CHK     include/generated/compile.h
  UPD     include/generated/compile.h
  CC      init/version.o
  AR      init/built-in.a
  LD      vmlinux.o
  MODPOST vmlinux.o
  MODINFO modules.builtin.modinfo
  LD      .tmp_vmlinux.btf
  BTF     .btf.vmlinux.bin.o
Killed
  LD      .tmp_vmlinux.kallsyms1
  KSYM    .tmp_vmlinux.kallsyms1.o
  LD      .tmp_vmlinux.kallsyms2
  KSYM    .tmp_vmlinux.kallsyms2.o
  LD      vmlinux
  SORTEX  vmlinux
  SYSMAP  System.map
  AS      arch/x86/boot/bioscall.o
  CC      arch/x86/boot/cmdline.o
  CC      arch/x86/boot/a20.o
  AS      arch/x86/boot/copy.o
  HOSTCC  arch/x86/boot/mkcpustr
  CC      arch/x86/boot/cpuflags.o
  CC      arch/x86/boot/cpucheck.o
  CC      arch/x86/boot/early_serial_console.o
  CC      arch/x86/boot/edd.o
  CC      arch/x86/boot/main.o
  CC      arch/x86/boot/memory.o
  LDS     arch/x86/boot/compressed/vmlinux.lds
  AS      arch/x86/boot/compressed/head_64.o
  CC      arch/x86/boot/pm.o
  VOFFSET arch/x86/boot/compressed/../voffset.h
  CC      arch/x86/boot/compressed/string.o
  AS      arch/x86/boot/pmjump.o
  CC      arch/x86/boot/printf.o
  CC      arch/x86/boot/compressed/cmdline.o
  CC      arch/x86/boot/compressed/error.o
  CC      arch/x86/boot/regs.o
  CC      arch/x86/boot/string.o
  OBJCOPY arch/x86/boot/compressed/vmlinux.bin
  CC      arch/x86/boot/tty.o
  RELOCS  arch/x86/boot/compressed/vmlinux.relocs
  CC      arch/x86/boot/video.o
  HOSTCC  arch/x86/boot/compressed/mkpiggy
  CC      arch/x86/boot/video-mode.o
  CC      arch/x86/boot/compressed/cpuflags.o
  CC      arch/x86/boot/compressed/early_serial_console.o
  CC      arch/x86/boot/version.o
  CC      arch/x86/boot/video-vga.o
  CC      arch/x86/boot/video-vesa.o
  CC      arch/x86/boot/compressed/kaslr.o
  CC      arch/x86/boot/video-bios.o
  HOSTCC  arch/x86/boot/tools/build
  CC      arch/x86/boot/compressed/kaslr_64.o
  CPUSTR  arch/x86/boot/cpustr.h
  AS      arch/x86/boot/compressed/mem_encrypt.o
  CC      arch/x86/boot/compressed/pgtable_64.o
  CC      arch/x86/boot/compressed/acpi.o
  CC      arch/x86/boot/compressed/eboot.o
  AS      arch/x86/boot/compressed/efi_stub_64.o
  AS      arch/x86/boot/compressed/efi_thunk_64.o
  CC      arch/x86/boot/compressed/misc.o
  GZIP    arch/x86/boot/compressed/vmlinux.bin.gz
  CC      arch/x86/boot/cpu.o
  MKPIGGY arch/x86/boot/compressed/piggy.S
  AS      arch/x86/boot/compressed/piggy.o
  LD      arch/x86/boot/compressed/vmlinux
  OBJCOPY arch/x86/boot/vmlinux.bin
  ZOFFSET arch/x86/boot/zoffset.h
  AS      arch/x86/boot/header.o
  LD      arch/x86/boot/setup.elf
  OBJCOPY arch/x86/boot/setup.bin
  BUILD   arch/x86/boot/bzImage
Setup is 17692 bytes (padded to 17920 bytes).
System is 9177 kB
CRC 54e6943b
Kernel: arch/x86/boot/bzImage is ready  (#3)

出现表示成功：

Setup is 17692 bytes (padded to 17920 bytes).
System is 9177 kB
CRC 54e6943b
Kernel: arch/x86/boot/bzImage is ready  (#3)

并找到编译好的 bzlmage镜像.

终于成功!!!

编译内核太不容易！

🤣🤩

总结

总体来说跟着ctfwiki来操作还是很好操作的.

意味着编译成功。在编译成功后，我们一般主要关注于如下的文件

bzImage：arch/x86/boot/bzImage
vmlinux：源码所在的根目录下。

此外，这里给出常见内核文件的介绍。

bzImage：目前主流的 kernel 镜像格式，即 big zImage（即 bz 不是指 bzip2），适用于较大的（大于 512 KB） Kernel。这个镜像会被加载到内存的高地址，高于 1MB。bzImage 是用 gzip 压缩的，文件的开头部分有 gzip 解压缩的代码，所以我们不能用 gunzip 来解压缩。
zImage：比较老的 kernel 镜像格式，适用于较小的（不大于 512KB） Kernel。启动时，这个镜像会被加载到内存的低地址，即内存的前 640 KB。zImage 也不能用 gunzip 来解压缩。
vmlinuz：vmlinuz 不仅包含了压缩后的 vmlinux，还包含了 gzip 解压缩的代码。实际上就是 zImage 或者 bzImage 文件。该文件是 bootable 的。 bootable 是指它能够把内核加载到内存中。对于 Linux 系统而言，该文件位于 /boot 目录下。该目录包含了启动系统时所需要的文件。
vmlinux：静态链接的 Linux kernel，以可执行文件的形式存在，尚未经过压缩。该文件往往是在生成 vmlinuz 的过程中产生的。该文件适合于调试。但是该文件不是 bootable 的。
vmlinux.bin：也是静态链接的 Linux kernel，只是以一个可启动的 (bootable) 二进制文件存在。所有的符号信息和重定位信息都被删除了。生成命令为：objcopy -O binary vmlinux vmlinux.bin。
uImage：uImage 是 U-boot 专用的镜像文件，它是在 zImage 之前加上了一个长度为 0x40 的 tag 而构成的。这个 tag 说明了这个镜像文件的类型、加载位置、生成时间、大小等信息。

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