技术

so动态库只导出指定函数

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retain_sym.txt

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func1
func2

ver_script.txt

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LIBA_1.1 {
	global:
		foo1;
		foo2;
	local:
		*;
};
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ld -shared --retain-symbols-file=retain_sym.txt --version-script=ver_script.txt tst.o -o tst.so

refer to:
https://blog.csdn.net/chdhust/article/details/79356717
http://blog.sina.com.cn/s/blog_493667730100csde.html
http://www.gnu.org/software/gnulib/manual/html_node/LD-Version-Scripts.html

linux命令备忘录

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名词

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pie: position-independent executable
pic: position-independent code
aslr: address space layout randomization
got: global offset table
vdso: virtual dynamic shared object

Basic command

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grep [OPTION]... PATTERNS [FILE]...
find [-H] [-L] [-P] [-Olevel] [-D debugopts] [path...] [expression]
find . -size +2G -exec du -sh {} \;
ps axl | grep VirtualBoxVM | grep -v grep | awk '{print $3};'
cat /etc/passwd | sort -k5,5 -t: | column -t -s:
while true; do echo sleep 1 sec; sleep 1; cat /home/work/aa.txt 2>/dev/null && echo ok && break; done
echo first | xargs -i echo {} second
 
cat /etc/shadow
sudo !!
 
cd other_dir
cd - # return back

swap文件

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dd if=/dev/zero of=./swap_file bs=1G count=8
mkswap ./swap_file
swapon ./swap_file
swapoff ./swap_file

objcopy

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objcopy -I binary -O elf32-i386 -B i386 test.jpg test.o
objdump -s -b binary test.o
readelf -s test.o

静态链编stdc++

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-Bstatic -lstdc++ -Bdynamic

工具

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systemtap
inotify-tools
windres
reptyr
nmcli
nmtui

自启动

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#/lib/systemd/system/mytask.service
#ln -s /lib/systemd/system/mytask.service /etc/systemd/system/multi-user.target.wants/mytask.service
[Unit]
Description=mytask
After=network.target
 
[Service]
Type=simple
ExecStart=mytask.sh
 
[Install]
WantedBy=multi-user.target

ubuntu

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#网络配置文件路径，默认DHCP的连接不会生成文件
/etc/NetworkManager/system-connections/
#run arm64 binary on x86
dpkg --add-architecture armhf && apt-get update && apt-get install libc6:armhf
cat /proc/sys/fs/binfmt_misc/
qemu-user -L /home/bamanzi/i386-libs ./prog
#disable background process
systemctl disable unattended-upgrades
ss -tap
pv -d <pid>

centos

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#网络配置文件路径
/etc/sysconfig/network-scripts/ifcfg-
#compiz
https://spins.fedoraproject.org/mate-compiz/download/index.html

refer to:
http://blog.chinaunix.net/uid-28461677-id-5766451.html
https://blog.csdn.net/weixin_33842304/article/details/91443399
https://unix.stackexchange.com/questions/4034/how-can-i-disown-a-running-process-and-associate-it-to-a-new-screen-shell
https://blog.csdn.net/wuzhong8809/article/details/117450302
https://stackoverflow.com/questions/18312935/find-file-in-linux-then-report-the-size-of-file-searched
https://www.toutiao.com/a7073448755428688399/
https://www.likecs.com/show-695436.html

Optimizing the kernel for VMware

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[*] 64-bit kernel (leave blank for x86)
 
General Setup --->
  [*] Optimize very unlikely/likely branches
 
Power management and ACPI options --->
  [*] ACPI (Advanced Configuration and Power Interface) Support --->
 
Processor type and features --->
  Processor Family (usually Core2/Newer Xeon)
 
Bus Options --->
  < > PCCard (PCMCIA/Cardbus) support
 
Networking support --->
  [ ] Amateur Radio support
  [ ] Wireless (only if you plan on using nat EXCLUSIVELY)
 
Device Drivers --->
  Generic Driver Options
    [*] Maintain a devtmpfs filesystem to mount at /dev
 
  Misc Devices --->
    [*] VMware Balloon Driver (manages memory between VM and host)
    [*] VMware VMCI Driver (Virtual Machine Communication Interface - low-latency access to host memory bus)
 
  SCSI device support --->
    [*] SCSI low-level drivers --->
      <*> VMware PVSCSI driver support (high throughput storage adapter)
 
  [*] Fusion MPT device support --->
    <*> Fusion MPT ScsiHost drivers for SPI
 
  [*] Network device support --->
    [*] Ethernet driver support --->
      (disable every driver but this)
      [*] AMD Devices
        <*> AMD PCNet32 PCI support
    [ ] Wireless LAN (ONLY if you disabled Wireless networking support above)
    < > VMware VMXNET3 ethernet driver (PCNet32 is more than enough for most use cases - enable this only if you have spare cpu cycles to burn)
 
  Graphics support --->
    <*> Direct Rendering Manager
    < > Intel 8xx/9xx/G3x/G4x/HD Graphics
    <*> DRM driver for VMware Virtual GPU
      [*] Enable framebuffer console support under vmwgfx by default
    <*> Support for frame buffer devices
 
    Console display driver support --->
      <*> Framebuffer Console support
 
  Sound card support --->
    <*> Advanced Linux Sound Architecture --->
      [*] PCI sound devices
        <*> (Creative) Ensoniq AudioPCI 1371/1373
        < > Intel HD Audio
 
  File systems --->
    (enable only those you anticipate using)
    <*> Second extended fs support
    <*> The Extended 4 (ext4) filesystem
    <*> XFS filesystem support
    <*> Btrfs filesystem Unstable disk format
 
    Pseudo filesystems --->
      [*] Tmpfs virtual memory file system support (former shm fs)
        [*] Tmpfs POSIX Access Control Lists

efi boot (uncertain, maybe need to ask pc maker for signing the kernel.)

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Processor type and features --->
  [*] EFI runtime service support 
  [*]   EFI stub support
Firmware Drivers  --->
   EFI (Extensible Firmware Interface) Support  --->
       <*> EFI Variable Support via sysfs

device mapper

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Device Drivers
	Multiple devices driver support (RAID and LVM)
		<M>   Device mapper support

refer to:
https://forums.gentoo.org/viewtopic-p-7332884.html
https://stackoverflow.com/questions/40344484/cant-load-self-compiled-linux-kernel

kprobe and uprobe

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kprobe

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cd /sys/kernel/debug/tracing
echo 'p:myprobe do_sys_open' > kprobe_events
echo 'r:myretprobe do_sys_open $retval' > kprobe_events
echo 'r:myprobe getname +0($retval):string' > kprobe_events
echo 1 > tracing_on
echo 1 > events/kprobes/myprobe/enable
echo '-:myprobe' > kprobe_events
cat trace

uprobe

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cd /sys/kernel/debug/tracing
echo 'p:do_sth /home/kernel_test/loop_print:0x52d %ip %ax' > uprobe_events
echo 'r:do_sth_exit /home/kernel_test/loop_print:0x52d %ip %ax' >> uprobe_events
echo 1 > events/uprobes/enable
cat trace

refer to:
https://blog.csdn.net/melody157398/article/details/113764679
https://blog.csdn.net/daiq531/article/details/52749673

asn.1中的方括号

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asn.1编码以tag + length + value为基本单元，IMPLICIT模式是用context-specific tag替换后面通常是universal的tag；EXPLICIT模式是用context-specific tag的tlv包裏里层的universal tag的tlv。

ber编码时，会默认为EXPLICIT模式。

在bnf范式语法中

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圆括号(): 相当于C语言算术表达式中圆括号()的作用。
尖括号<>: 内包含的为必选项。 
方括号[]: 内包含的为可选项。 
花括号{}: 内包含的为可重复0至无数次的项。 
|: 或or的意思；若要表示并and的意思，直接两个符号之间空白间隔。

而在asn.1语法中，方括号[Index]指示的是context-specific tag值，即0xA0 + Index；花括号{}用于SEQUENCE，SET或CHOICE的定义。如

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Number2 ::= [7] IMPLICIT [1] INTEGER
AccountedClosed ::= [2] EXPLICIT BOOLEAN

这里Number2的tag值为0xA7；而对于AccountedClosed，当其值为true时其ber编码为

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0xA2 0x3 0x1 0x1 0xFF

refer to:
https://blog.csdn.net/sever2012/article/details/7767867
https://www.cnblogs.com/qook/p/5957436.html

数字证书备忘录

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ca: certification authority
pem: privacy enhanced mail, "begin"+base64+"end"
der: distinguished encoding rules, binary
crt: certificate
cer: certificate
csr: certificate signing request
pkcs: public key cryptography standard
ietf: internet engineering task force
pkcs#12/pfx/p12: file format encoding private keys, certificates and etc, rfc7292
pkcs#7: cryptographic message syntex standard
pkcs#10/p10: certification request syntax specification, rfc2986
x.509: public key certificates format standard
ber: basic encoding rules
per: packed encoding rules
crl: certificate revocation list
dsa: digital signature algorithm

refer to:
http://www.360doc.com/content/15/0520/10/21412_471902987.shtml
https://baike.baidu.com/item/BER/19940289?fr=aladdin
https://blog.csdn.net/mao834099514/article/details/109074661
https://datatracker.ietf.org/doc/html/rfc7292

转载: linux下的多国语言解决方案

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hello.c

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#include <stdio.h>
#include <libintl.h> // gettext
#include <locale.h>
 
#define _(STRING) gettext(STRING)
#define PACKAGE "hello"
#define LOCALEDIR "/usr/share/locale/"
 
int main(int argv, char* argc[])
{
	setlocale(LC_ALL, "");
	bindtextdomain(PACKAGE, LOCALEDIR);
	textdomain(PACKAGE);
	printf(_("Hello, World\n"));
	printf(_("This is a example.\n"));
	return 0;
}

提取字符串

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xgettext --keyword=_ hello.c -o hello.pot

编辑hello.pot

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...
msgid "Hello, World\n"
msgstr "大家好！\n"
msgid "This is a example.\n"
msgstr "This is a example.\n"
...

将hello.pot编译为字节码

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msgmerge zh_CN.po hello.pot
msgfmt zh_CN.po -o hello.mo

refer to:
https://leedd.com/linux-c-i18n-l10n-xgettext-msgfmt-rpmbuild/

linux驱动备忘录

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驱动签名

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CONFIG_MODULE_SIG=y
# CONFIG_MODULE_SIG_FORCE is not set
CONFIG_MODULE_SIG_ALL=y
 
${KERNEL_SRC}/scripts/sign-file sha512 ${KERNEL_SRC}/certs/signing_key.pem ${KERNEL_SRC}/certs/signing_key.x509 hello.ko

驱动调试

debugee

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MOD_NAME=simple_mod
insmod ./${MOD_NAME}.ko
MOD_TEXT=`cat /sys/module/${MOD_NAME}/sections/.text`
MOD_DATA=`cat /sys/module/${MOD_NAME}/sections/.data`
MOD_BSS=`cat /sys/module/${MOD_NAME}/sections/.bss`
MOD_ADD="add-symbol-file /path/to/${MOD_NAME}.ko ${MOD_TEXT} -s .data ${MOD_DATA} -s .bss ${MOD_BSS}"
echo ${MOD_ADD}

debugger

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(gdb) ${MOD_ADD}

refer to:
https://www.cnblogs.com/rivsidn/p/9481037.html
https://www.cnblogs.com/powerrailgun/p/12161295.html
https://blog.csdn.net/chdhust/article/details/8820628