SGH_WIKI - mywiki:linux

cache

Anonymous (anonymous@undisclosed.example.com) — 2019-09-15T10:55:28+00:00

Linux Cache Operation & Address Conversion Linux Cache Operation opt Term API Invalidate stale data problem dma_cache_inv(unsigned long address unsigned long size) Flush/write back any dirty cache dma_cache_wback/dma_cache_wback_inv(unsigned long address, unsigned long size)

checksum

Anonymous (anonymous@undisclosed.example.com) — 2019-09-15T10:55:28+00:00

Linux Checksum Calculation Logic API Comments skb_checksum_help ip_fast_csum csum_fold skb_checksum csum_tcpudp_magic nf_ip_checksum csum_tcpudp_nofold csum_replace4 csum_replace2 nf_nat_ipv4_csum_recalc csum_tcpudp_magic skb->csum_start = skb_transport_header(skb) - skb

chrootenv

Anonymous (anonymous@undisclosed.example.com) — 2022-04-02T09:30:06+00:00

How to set up a chroot environment with RedHat Linux 6.2 Set up chroot environment via backup from real system * C library (libc/glibc) * Resolver for nameservices (DNS, NIS, ...) * Authentication information (/etc/passwd, group, shadow, ...)

code_analysis

Anonymous (anonymous@undisclosed.example.com) — 2019-09-15T10:55:28+00:00

Code Analysis Tools Sparse Sparse is a tool for static code analysis that helps kernel developers to detect coding errors. Kernel code that is prone to mistakes is annotated by kernel developers using the 'attribute' specifiers. Sparse tool uses these specifiers to pinpoint coding mistakes. For details, refer to

colorconsole

Anonymous (anonymous@undisclosed.example.com) — 2022-04-02T09:30:06+00:00

Linux Color Console \033[22;30m - black \033[22;31m - red \033[22;32m - green \033[22;33m - brown \033[22;34m - blue \033[22;35m - magenta \033[22;36m - cyan \033[22;37m - gray \033[01;30m - dark gray \033[01;31m - light red \033[01;32m - light green \033[01;33m - yellow \033[01;34m - light blue \033[01;35m - light magenta \033[01;36m - light cyan \033[01;37m - white

crosscompile

Anonymous (anonymous@undisclosed.example.com) — 2022-04-02T09:30:04+00:00

Cross Compile for Embedded System (MIPS) PHP-CGI ../configure --prefix=../result/php-5.3.5 --host=i686-pc-linux-gnu --target=mipsel-linux-gnu --build=mipsel-linux-gnu --enable-cgi --disable-all --without-pear --with-config-file-path=/etc/ lighttpd

ctools

Anonymous (anonymous@undisclosed.example.com) — 2019-09-15T10:55:28+00:00

Get Interface IP address in Kernel Binary file replace from file2 to file1 [Linux Proc Wrapper to provide simple proc implementation] Linux Color console with printk IP Checksum APIs Map enum to string

debugging

Anonymous (anonymous@undisclosed.example.com) — 2020-08-09T08:10:12+00:00

[GDB]

device_tree

Anonymous (anonymous@undisclosed.example.com) — 2019-09-15T10:55:28+00:00

Device Tree Reference Device_Tree_Usage Youtube DTS ePAPR specification Runtime check device tree content cat /proc/device-tree/xxx

dhcpv6

Anonymous (anonymous@undisclosed.example.com) — 2019-09-15T10:55:28+00:00

DHCPV6 Reference DHCP Mode O Flag M Flag Meaning 0 0 Router has everything like Prefix, Prefix-length, Default Gateway, DNS, ... 1 0 Router has most configuration except some information such as DNS addresses should get from a DHCPv6 server

enum_string

Anonymous (anonymous@undisclosed.example.com) — 2019-09-15T10:55:28+00:00

Map Enum to string array or its value array #define DP_F_FLAG_LIST \ DP_F_ENUM_OR_STRING(DP_F_DEREGISTER, 0x00000001, "De-Register"), \ DP_F_ENUM_OR_STRING(DP_F_FAST_ETH_LAN, 0x00000002, "ETH_LAN"), \ DP_F_ENUM_OR_STRING(DP_F_FAST_ETH_WAN, 0x00000004, "ETH_WAN"),\ DP_F_ENUM_OR_STRING(DP_F_FAST_WLAN, 0x00000008, "FAST_WLAN"),\

fedora

Anonymous (anonymous@undisclosed.example.com) — 2022-04-02T09:30:02+00:00

Fedora Reference Torrent Download Link Install Fedora via local Network ftp Linux Commons Configuration and Issues PPA App Lists

fedora_firewall

Anonymous (anonymous@undisclosed.example.com) — 2022-04-02T09:30:02+00:00

Fedora 20 Samba Server setup Install samba RPM yum install cups-libs samba samba-common samba-client system-config-samba Configure samba /etc/samba/smb.conf Disable firewall/seclinux #Disable firewall otherwise windows cannot see the PC systemctl stop firewalld #temporarily stop firewall

filereplace

Anonymous (anonymous@undisclosed.example.com) — 2022-04-02T09:30:02+00:00

This tool is used to replace first binary file at specified offset Binary file1, Binary file2, Final file: part of file1 + file2 + part of file1. Note: File1 file length no change. #include #include #include char *ReadFile(char *name, int *len) { FILE *file; char *buffer; unsigned long fileLen; //Open file file = fopen(name, "rb"); if (!file) { fprintf(stderr, "Unable to open file %s", name); return NULL; } //Get file length fseek(file, 0, SE…

generic_netlink

Anonymous (anonymous@undisclosed.example.com) — 2019-09-15T10:55:28+00:00

Generic Netlink Reference Generic Netlink Howto Generic Netlink详解 Linux Generic Netlink 设计与实现 Generic Netlink Architecture Generic Netlink communications are essentially a series of different communication channels which are multiplexed on a single Netlink family. Communication channels are uniquely identified by channel numbers which are dynamically allocated by the Generic Netlink controller.

intel

Anonymous (anonymous@undisclosed.example.com) — 2022-04-02T09:30:02+00:00

Processor Name 32- or 64-bit Intel Core Solo 32 bit Intel Core Duo 32 bit Intel Core 2 Duo 64 bit Intel Quad-Core Xeon 64 bit Dual-Core Intel Xeon 64 bit Quad-Core Intel Xeon 64 bit Core i3 64 bit Core i5 64 bit Core i7 64 bit

ipsec

Anonymous (anonymous@undisclosed.example.com) — 2019-09-15T10:55:28+00:00

IPSec Implementation in Linux Reference [ ipsec_xfrm ] IPSEC Basic Security Scheme Difference IPSEC Security scheme operating in the Internet Layer of the Internet Protocol Suite TLS/SSH Security scheme operating in the upper layers of the TCP/IP model, like transport layer

ip_checksum_apis

Anonymous (anonymous@undisclosed.example.com) — 2019-09-15T10:55:28+00:00

IP Checksum APIs IP Header Checksum Calculation Implementation /* set ip checksum of a given ip header*/ void compute_ip_checksum(struct iphdr *iphdrp) { iphdrp->check = 0; iphdrp->check = compute_checksum((unsigned short *)iphdrp, iphdrp->ihl << 2); } /* Compute checksum for count bytes starting at addr, using one's complement of one's complement sum*/ static unsigned short compute_checksum(unsigned short *addr, unsigned int count) { register unsigned long sum = 0; while (count > 1) { …

ip_kernel

Anonymous (anonymous@undisclosed.example.com) — 2022-04-02T09:30:00+00:00

Get Interface IP adderss in Linux Kernel Method struct net_device { ... struct in_device __rcu *ip_ptr; /* IPv4 specific data */ struct inet6_dev __rcu *ip6_ptr; /* IPv6 specific data */ ... } Example 1 #include #include #include #include #include #include MODULE_DESCRIPTION("Test Module"); MODULE_AUTHOR("Gilboa Davara"); MODULE_LICENSE("GPL"); sta…

ip_routing

Anonymous (anonymous@undisclosed.example.com) — 2019-09-15T10:55:28+00:00

IP Routing In Linux Reference:

kernelothers

Anonymous (anonymous@undisclosed.example.com) — 2019-09-15T10:55:28+00:00

Others MIPS CPU Utilization Metric Formula MIPS(Million Instruction per second) (instr_cnt/cycle_cnt) * CPU_clock CPI (Cycles per instruction) cycle_cnt/instr_cnt CPU_utilization cycle_cnt/CPU_clock CPU_wasted stall_cycle_cnt / cpu_clock CPU_idle

kgdb

Anonymous (anonymous@undisclosed.example.com) — 2022-04-02T09:29:58+00:00

Kernel debugging kgdb Reference GDB commands Examining Symbol Linux Kernel coding style: * * Documentation/process/coding-style.rst Linux Kernel documentation: for example of linux kernel 5.0 * * Kernel configure kgdb内核配置 * 在 menuconfig 中选中 Kernel hacking

lighttpd

Anonymous (anonymous@undisclosed.example.com) — 2022-04-02T09:29:58+00:00

lighttpd porting reference: CC="mips-linux-gcc -I/tmp/rootfs/lighttpd/include -L/tmp/rootfs/lighttpd/lib" LD="mips-linux-ld -L/tmp/rootfs/lighttpd/lib" ./configure --target=mips-linux --host=mips-linux --without-zlib --prefix=/tmp/rootfs/lighttpd --without-bzip2 --disable-ipv6 --with-pcre=/tmp/rootfs/lighttpd/lib/ ----------------------------------------------------- 設定 lighttpd.conf …

linuxadmin

Anonymous (anonymous@undisclosed.example.com) — 2019-09-15T10:55:28+00:00

Linux Admin Reference Useful Linux Commands SSH Schedule routine with crone Linux cron utility is an effective way to schedule a routine background job at a specific time and/or day on an on-going basis. Display all scheduled routine crontab -l Add a scheduled routine

linuxcommands

Anonymous (anonymous@undisclosed.example.com) — 2022-04-02T09:29:54+00:00

tar commnad and usage tar usage Example Create tar Archive File .tar tar -cvf tecmint-14-09-12.tar /home/tecmint/ c – Creates a new .tar archive file. v – Verbosely show the .tar file progress. -f – File name type of the archive file. Create tar.gz Archive File

linuxdma

Anonymous (anonymous@undisclosed.example.com) — 2022-04-02T09:29:54+00:00

Linux DMA DMA Zone Reference: Because of hardware limitations, the kernel cannot treat all pages as identical. Some pages, because of their physical address in memory, cannot be used for certain tasks. Because of this limitation, the kernel divides pages into different zones. The kernel uses the zones to group pages of similar properties. In particular, Linux has to deal with two shortcomings of hardware with respect to memory addressing:

linuxmoduleinitorder

Anonymous (anonymous@undisclosed.example.com) — 2022-04-02T09:29:54+00:00

Linux Module Initialization Order For static linked to Kernel case Below is the initialization order from first to last. For details, refer to linux/init.h * core_initcall() * postcore_initcall() * arch_initcall() * subsys_initcall() * fs_initcall()

linuxmoduleorder

Anonymous (anonymous@undisclosed.example.com) — 2019-09-15T10:55:28+00:00

Linux Module Initialization Sequence See the include file: include/linux/init.h for a list of the macros and their ordering. The order specified there is: early_initcall: like itc, vmb pure_initcall: core_initcall: like gptu, ngi postcore_initcall：　like dma, arch_initcall: like timer, reset, **prom** subsys_initcall: like ath9k_eeprom fs_initcall rootfs_initcall device_initcall: like hwmcpy, late_initcall

linuxnetworking

Anonymous (anonymous@undisclosed.example.com) — 2019-09-15T10:55:28+00:00

Linux Networking SKB Notes [IPv6 Neighbor Discovery] DHCPv6 [Multicast/IGMP] IPSEC IP Routing Samba checksum Page allocation OSI layer Layer Name Description 7 Application e.g. HTTP, SMTP, SNMP, FTP, Telnet, SSH and Scp, NFS, RTSP etc. 6 Presentation e.g. XDR, ASN.1, SMB, AFP etc 5 Session e.g. TLS, SSH, ISO 8327 / CCITT X.225, RPC, NetBIOS, ASP etc.

linuxstack

Anonymous (anonymous@undisclosed.example.com) — 2022-04-02T09:29:52+00:00

Linux Stack Overflow and Buffer Over Reference Linux Kernel Stack kernel Stack The default stack size for a process running in kernel space is 8K (as of 2011). exception/hard IRQ/soft IRQ stack hardware stack: hardirt_stack array softIRQ stack: softirt_stack array

linux_bus

Anonymous (anonymous@undisclosed.example.com) — 2019-09-15T10:55:28+00:00

Linux Buses/Devices/and Drivers Reference [Kernel Slides] Linux Device Drivers, Third Edition bus a channel between the processor and one or more devices. It is represented by struct bus_type. Commonly it can be dynamically detected, like PCI, USB It can be virtual or physical, All devices are connected to a bus

linux_code_sparse_test_anaylysis

Anonymous (anonymous@undisclosed.example.com) — 2019-09-15T10:55:28+00:00

Linux Code Sparse Test/Analysis klockwork Sparse Get sparse You can get sparse from git://git.kernel.org/pub/scm/devel/sparse/sparse.git Using sparse To use sparse for kernel development simply pass on the C=1 argument onto your make command. For example to enable sparse for mac80211 development you would use:

linux_debugging_with_lauterbach

Anonymous (anonymous@undisclosed.example.com) — 2019-09-15T10:55:28+00:00

Linux Debugging Reference Linux Debugging with LauterBach Basic requirement In order to support c source code level debugging, it is a must to enable debugging option during compile Get source code directory base mips-openwrt-linux-objdump -g vmlinux | grep -i DW_AT_comp_dir | grep -i indirect | grep '\/'

linux_kernel_notes

Anonymous (anonymous@undisclosed.example.com) — 2019-09-15T10:55:28+00:00

MIPS Porting Guide Kernel Context knowledge process context includes user context, kernel thread, work queue User Context The kernel executing on behalf of a particular process (ie. a system call or trap, ioctl, module_init, module_exit or kernel thread, workqueue. You can tell which process with the current macro.) Not to be confused with userspace. Can be interrupted by software or hardware interrupts.

linux_locking

Anonymous (anonymous@undisclosed.example.com) — 2022-04-02T09:29:56+00:00

Linux内核中的各种锁 RCU RCU(Read-Copy Update)，顾名思义就是读-拷贝修改，它是基于其原理命名的。对于被RCU保护的共享数据结构，读者不需要获得任何锁就可以访问它，但写者在访问它时首先拷贝一个副本，然后对副本进行修改，

linux_self-learning

Anonymous (anonymous@undisclosed.example.com) — 2019-09-15T10:55:28+00:00

Linux Self learning Reference Porting Guide Console The Linux kernel is configured to select the console by passing it the console parameter, for example: console=ttyLTQ0,115200 It can be checked via cat /proc/cmdline DMA DMA Engine/LTQ HW Memcpy(ltq_hwmcpy.c)/netowrk: CONFIG_NET_DMA

linux_soding_style

Anonymous (anonymous@undisclosed.example.com) — 2022-04-02T09:29:56+00:00

Linux Coding Style Reference Formatting Tools Code generally has to follow the Linux coding style to be accepted. Basically there are two tools for formatting the code: indent and astyle indent The indent program, an excellent GNU utility found on most Linux systems, formats source according to given rules. Refer to

mount_filesystem

Anonymous (anonymous@undisclosed.example.com) — 2022-04-02T09:29:52+00:00

Mount file system NFS refer to Mounting a remote file system via CLI command sudo mount host:/var/nfs/general /nfs/general For example: sudo mount 10.226.45.1:/var/nfs/general /nfs/general umount: sudo umount /nfs/general Mounting a remote file system on startup

network_data_flow_through_kernel.png

Anonymous (anonymous@undisclosed.example.com) — 2019-09-15T10:55:28+00:00

network_debugging

Anonymous (anonymous@undisclosed.example.com) — 2019-09-15T10:55:28+00:00

Linux Network Proc/Debugging Network device's MIB counters: cat /proc/net/dev Note: it should match with ifconfig command Inter-| Receive | Transmit face|bytes packets errs drop fifo frame compress multicast|bytes packets errs drop fifo colls carrier compress eth0_1: 101570 541 0 0 0 0 0 0 936 12 0 0 0 0 0 0 eth0_5: 0 0 0 0 0 0 0 0 0 0 0 0…

network_driver_notes

Anonymous (anonymous@undisclosed.example.com) — 2019-09-15T10:55:28+00:00

Network Driver Notes Reference Linux Device Drivers, 2nd Edition ifconfig eth0 up IFF_UP dev->open() ifconfig eth0 down ? dev->close() ifconfig eth0 hw ether 08:00:00:00:00:01 ioctl(SIOCSIFADDR) IFF_UP dev->set_mac_address dev->open

notes

Anonymous (anonymous@undisclosed.example.com) — 2022-04-02T09:29:50+00:00

Fedora Notes Confiugration Install Local yum repository based on Fedora 20 DVD ISO Install patch(yum) from local ISO Set sudo for one user #su - # #Suppose Set user sampleusername to administrator #usermod sampleusername -a -G root Or directly add below line into /etc/sudoers file:

office_linux_maintenance

Anonymous (anonymous@undisclosed.example.com) — 2019-09-15T10:55:28+00:00

Auto Save TWIKI to SVN with crontab TWIKI Server: 10.64.44.136 Auto save Twiki setup with crontab, ie, at every hour: * add user “shaoguoh” to group www-data * crontab -e #under user shaoguoh since shaoguoh is a user for svn commit 0 * * * * cd /mnt/data/www/twiki && ../s_add_wiki_new_file

openwrt

Anonymous (anonymous@undisclosed.example.com) — 2019-09-15T10:55:28+00:00

OpenWRT Feeds Reference: Feed is a collection of packages which share a common location. Feeds may reside on a remote server, in a version control system, on the local filesystem, or in any other location addressable by a single name (path/URL) over a protocol with a supported feed method. Feeds are additional predefined package build recipes for OpenWrt Buildroot.

optimize_options

Anonymous (anonymous@undisclosed.example.com) — 2019-09-15T10:55:28+00:00

GCC Optimize Options Reference Optimize-Options inline-functions -finline-functions 　　Integrate all simple functions into their callers. The compiler heuristically decides which functions are simple enough to be worth integrating in this way. 　　If all calls to a given function are integrated, and the function is declared

page_allocation

Anonymous (anonymous@undisclosed.example.com) — 2019-09-15T10:55:28+00:00

Reference Address Conversion page to Virtual address struct page *page; unsigned char *p; p = page_address(page); Other APIs: * kmap_atomic * __kunmap_atomic Linux Page Allocation Allocate pages struct page *page; page = alloc_pages(gfp, order);

ppalists

Anonymous (anonymous@undisclosed.example.com) — 2022-04-02T09:29:48+00:00

PPA Application Lists Basic Applications telnet For remote login to CPE's telnet server to start some daemon ftp client for remote login to CPE's server bash test automation script python test automation script perl test automation script

printk_proc

Anonymous (anonymous@undisclosed.example.com) — 2019-09-15T10:55:28+00:00

Linux printk Display Current timestamp status cat /sys/module/printk/parameters/time Enable printk timestamp echo yes > /sys/module/printk/parameters/time Disable printk timestamp echo no > /sys/module/printk/parameters/time

profiling_trace

Anonymous (anonymous@undisclosed.example.com) — 2019-09-15T10:55:28+00:00

Linux Kernel Profiling and Trace: Reference Part 1 Part 2 ftrace

samba

Anonymous (anonymous@undisclosed.example.com) — 2019-09-15T10:55:28+00:00

Samba Tuning Reference Samba tunning mmap and DMA Main Technique CONFIG_NET_DMA to offload TCP copy from kernel to userspace ?? zero copy kernel bypass min receivefile size This option changes the behavior of Samba when processing write calls. Any incoming write call on a non-signed SMB/CIFS connection greater than this value will not be processed in the normal way but will be passed to any underlying kernel recvfile or splice system call (if there is no such call Samba will emulate in…

skb

Anonymous (anonymous@undisclosed.example.com) — 2022-04-02T09:29:46+00:00

SKB Knowledge Reference [ SKB API(Chinese)] SKB Notes len the size of a complete input packet including headers. This value includes data in the kmalloc'd part, fragment chain and/or unmapped page buffers. data_len the number of bytes in the fragment chain and in unmapped page buffers and is normally 0.

ssh

Anonymous (anonymous@undisclosed.example.com) — 2019-09-15T10:55:28+00:00

SSH Login Without Password Using ssh-keygen & ssh-copy-id Suppose need to use ssh to login to remote PC B from local PC A * Create public and private keys using ssh-key-gen at At PC A Take note: make sure use empty passphrase for auto login without password case

start

Anonymous (anonymous@undisclosed.example.com) — 2025-08-29T02:58:20+00:00

Welcome to the Linux World Shortcut Linux Cross Reference [Kernel API List] Linux Device Drivers, Third Edition [Kernel Slides] Linux Debugging Cache & Address conversion Linux Self-Learning Linux Admin Set up Environment for chroot Linux Coding Style Linux Kernel Linux Kernel Notes [Kernel Locking] [Linux Hacking] Chinese TCP/IP Linux Kernel Networking DMA Linux Stack Linux Locking [Linux Inerrupt.ppt] Linux Kernel module initialize order Network Debugging…

sysfs

Anonymous (anonymous@undisclosed.example.com) — 2019-09-15T10:55:28+00:00

Linux Sysfs Documents

tc-ca

Anonymous (anonymous@undisclosed.example.com) — 2025-08-29T08:35:54+00:00

Difference between ingress/egress qdisc Feature Ingress Qdisc egress Qdisc Direction Incoming traffic Outgoing traffic Common Usage Policing (rate limiting) Shaping, scheduling Handle ffff: Custom (e.g., 1:) Parent Keyword parent ffff:

tcp

Anonymous (anonymous@undisclosed.example.com) — 2019-09-15T10:55:28+00:00

Reference [TCP Implementation in Linux] TCP Entry: tcp_v4_rcv

tcp_performance

Anonymous (anonymous@undisclosed.example.com) — 2022-04-02T09:29:44+00:00

Formula for TCP Performance/Latency/Window Size Formula Bits-per-second-throughput = TCP-Window-Size-in-bits / Latency-in-seconds Optimal TCP window size in bytes = Bandwidth-in-bits-per-second * Round-trip-latency-in-seconds = TCP window size in bits / 8

ubuntu

Anonymous (anonymous@undisclosed.example.com) — 2020-08-09T08:10:12+00:00

How to Setup Ubuntu for PPA automation (based on Ubunut 14.04.1) Reference Vmplayer Office Linux maintenance Ubuntu 16.04 Update ubuntu via apt-get $ sudo apt-get update $ sudo apt-get install update-manager-core $ sudo do-release-upgrade -d PPA Ubuntu template with basic applications/servers

ubuntu_16.04

Anonymous (anonymous@undisclosed.example.com) — 2019-09-15T10:55:28+00:00

create a customized daemon via systemd Create a ppa.service under folder /etc/systemd/system sudo chmod +x /etc/systemd/system/ppa.service sudo systemctl enable ppa sudo systemctl status ppa sudo systemctl daemon-reload File /etc/systemd/system/ppa.service

vmplayer

Anonymous (anonymous@undisclosed.example.com) — 2022-04-02T09:29:44+00:00

VMPlayer in Windows vmplayer Bios Add below line in vmx file to increase bootdelay time bios.bootdelay = 20000 F2 button to key BIOS Map multiple network adapter to bridged mode in vmplayer Based on Vmplayer v6.0.1 in Windows 7 Download vmplayer v6.0.1 and install it.

websvn

Anonymous (anonymous@undisclosed.example.com) — 2019-09-15T10:55:28+00:00

WebSVN setup in Ubuntu 14.04 Since WEBSVN does not fully compatible with Ubuntu 14.04 yet. So we have to do some trick here First uninstall failed websvn if already tried sudo apt-get remove websvn sudo apt-get remove --auto-remove websvn sudo apt-get purge websvn

yumlocaliso

Anonymous (anonymous@undisclosed.example.com) — 2022-04-02T09:29:42+00:00

Setup yum repositories to update or install package from Local ISO Image Creation of yum repositories is handled by a separate tool called createrepo, which generates the necessary XML metadata. If you have a slow internet connection or collection of all downloaded ISO images, use this hack to