mmap mindmap

data cache to be provided by the receiver, the receiver does not know exactly how large the cache is enough, can only open as much space or call the API to receive the message header to obtain the size of the message body, and then open up the appropriate space to receive the message body. Both approaches are inadequate, not a waste of space or a waste of time.Binder employs a new strategy: the binder driver is responsible for managing the data receive cache. We note that the binder driver impl

files under/proc/{pid}/.If a process contains multiple threads, multiple threads share a process's user-state virtual address space, and the virtual address space contains several areas, mainly in the following areas:1. The code snippet of the current execution file, which is called the text segment.2, the execution of the data section of the file, the main store to execute the file to use the global variables, static variables. (Global and Static)3. A heap that stores global variables and dyna

= 100M//above parameters can be defined by yourself nbsp; step three: Check to see if you support PHP APC apc_store apc_fetch Check phpinfo for APC dependencies nbsp; B.LIUNX Install APC first step: Download and install wget http://pecl.php.net/get/APC-3.1.8.tgz tar-zxvf apc-3.1.8.tgz cd apc-3.1.8/usr/local/php/bin/phpize./ Configure--ENABLE-APC--enable-mmap--enable-apc-sPinlocks--disable-apc-pthreadmutex--with-php-config=/usr/local/php/bin/php-confi

is enough to support a display device in an embedded system. The frame buffer device is a standard character device, the main device number is 29, and the secondary device number is 0 to 31. correspond to/dev/fb0-/dev/fb31 respectively. With /DEV/FB, there are several main operations of the application: 1. Read/write (read/write)/DEV/FB: equivalent to a read/write screen buffer. For example, the CP/DEV/FB0 tmp command allows the contents of the current screen to be copied to a file, while the c

allocate a video buffer (apply for V4L2 video driver to allocate memory). V4L2 is the driver layer of the Video device and is located in the kernel space, therefore, the memory requested by using the VIDIOC_REQBUFS control command word is in the kernel space and cannot be accessed directly by applications. After you call the mmap memory ing function to map the kernel space memory to the user space, applications access the kernel space by accessing th

(, ipc_rmid ,); Function: maps shared memory objects to the process address space.Prototype void * MMAP (void * ADDR, size_t Len, int Prot, int flags, int FD, off_t offset );ParametersADDR: the starting address to be mapped. It is usually specified as null to allow the kernel to automatically selectLen: number of bytes mapped to the process address spaceProt: ing protection modeFlags: FlagFD: file descriptorOffset: the offset starting from the file

stores water. The CPU puts the result after the operation into this pool, and the pool then streams the result to the monitor. Data is not processed in the middle. Applications can also directly read and write the contents of this pool. In this mechanism, although framebuffer requires the support of a real video card driver, all the display tasks are completed by the CPU, so the CPU Heavy Load The device files of framebuffer are usually/dev/fb0,/dev/Fb1, and so on. Run the following command: #

divided the article into two parts: the previous section mainly introduces some basic concepts and relationships in heap memory management, it also focuses on the implicit linked list Technology Used in heap chunk allocation and release policies. The second part mainly introduces glibc malloc, the display linked list technology introduced to improve the efficiency of heap memory allocation and release, that is, the concept and core principle of binlist. The source code used is as follows: Https

This article by the embedded Penguin Circle original team member-Ali engineer Hao share.First, commit and applyApply is asynchronous, commit is synchronous, using commit in the main thread can affect performance, because synchronous IO operations can be lengthy, and two methods ensure that value is saved correctly to disk. Both are the methods of the editor class, and their implementation is in the Editorimpl class, and we'll compare these two functions in a rough way:Both functions call the Com

The memory manager of PHP is hierarchical. This manager has three layers: storage, heap, and emalloc/efree. The storage layer uses functions such as malloc () and mmap () to apply for memory from the system, and releases the applied memory through the free () function. The storage layer usually applies for a large amount of memory blocks. Here we apply for "> The memory manager of PHP is hierarchical. This manager has three layers: storage, heap,

5577 Dalvik Other 700 700 0 0 Stack 508 508 0 0 Other dev 33564 32600 4 0 .so mmap 9019 1244 7268 0 .apk mmap 101 0 16 0 .ttf

; sendpage is empty, and Sock-> OPS-> sendpage may be empty. What will happen if a function pointer with a null value is called in our program? Naturally, the program crashes, that is, the crash. So how can such a thing be exploited to steal the root identity? Let's gradually interpret the code given in the above link.Main function main ():Char template [] = "/tmp/padlina. xxxxxx ";Int fdin, fdout;Void * page;Uid = getuid (); // obtain the user ID, which is useful laterGid = getgid (); // obtain

system, so a device file node (/dev/fb0) is created automatically. The first part of the use of our application layer is to open the device file.(2) The second step is to obtain the device information (#include (3) Step three, mmap mapping. Because the application layer program is working on its own virtual address space, our driver is working in the kernel's address space. The driver has already applied for a piece of memory in the kernel, the memor

. Some hardware can bypass the main memory altogether and transmit data directly to another. This feature eliminates a copy in the system memory and are a nice thing to have, but does all hardware supports it. The There is also the issue of the the the ' the ' the ' the ' is ' repackaged for the network, which introduces some ions. To eliminate overhead, we could start by eliminating some of the copying between the kernel and user buffers. One way to eliminate a copy are to skip calling read and

. The code of the dynamic library used by the program. A heap that stores global variables and dynamically produces data. Holds the stack of local variables and implementation Function procedure calls. The segment of the Environment Change and command line arguments. A memory map that maps the contents of a file to a virtual address space. Process virtual address space mapping structure of the following two kinds of structure, in the case of the address space is not rich

the input file to the shared memory area, and the other from the shared memory area to the output file. In fact, when you share memory between processes, you do not always have to read and write small amounts of data, and then re-establish the shared memory area when there is new communication. Instead, the shared area is maintained until the communication is complete, so that the data content is kept in shared memory and is not written back to the file. Content in shared memory is often writte

Article title: advanced return library function Exploit code implementation (bottom ). Linux is a technology channel of the IT lab in China. Includes basic categories such as desktop applications, Linux system management, kernel research, embedded systems, and open source. 　　 9 attachment: README. code Prepare defective programs for compilation. $ Gcc-o vuln. omit-fomit-frame-pointer vuln. c $ Gcc-o vuln. c $ Gcc-o pax. c Ex-move.c ~~~~~~~~~~~~ The front part of the ex-move.c code predefines som

design philosophy. At present, in addition to the early Mmap storage engine, Wiredtiger and ROCKSDB have completed the support for MongoDB, the former is the acquisition of MongoDB company is directly introduced into the MONGODB 3.0 version. The introduction of the plug-in storage engine API has made it possible for MongoDB to enrich its arsenal to handle more different types of business, with memory storage engines, transactional storage engines, an

file is modified, the cache entries allocated to the old version of the memory will not be recycled until the TTL value set by this parameter reaches. Setting 0 is to disable this feature. Apc. cache_by_default Boolean typeThe default value is On, but it can be set to Off and used with apc. filters starting with the plus sign. the file is cached only when the filter is matched. Apc. filters stringA list of POSIX extension regular expressions separated by commas. If any mode matches the source f

or glibc. The memory management mechanism of glibc in Linux is roughly as follows: From the operating system perspective, the memory allocation of processes is completed by two system calls: BRK and MMAP. BRK is the highest address pointer _ edata to the high address of the Data Segment (. Data)Push, MMAP finds a free space in the virtual address space of the process. Among them, the memory allocated by