The Linux Kernel: System Calls M-R

Discussion in 'Linux Kernel' started by DevynCJohnson, Apr 20, 2014.

  1. DevynCJohnson

    DevynCJohnson Well-Known Member Staff Member Staff Writer

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    Aloha, here are some more system calls to discuss. Remember, this is not a complete list. Some syscalls have become obsolete and others are platform specific.

    mremap() - Memory REMAP is a syscall that remaps a virtual memory address. This means the kernel call gets a section of data and changes the size and location of that data's allocated area in memory.

    msync() - As many people may know, when a file is edited (for example, a plain text file), the file is loaded to memory and changes take place there. To save the changes to the hard-drive, msync() synchronizes the file on RAM with the older file on the hard-drive.

    nanosleep() - Like the sleep command commonly used in shell scripts, this command suspends execution on that thread. However, this command works on the nano-scale level.

    nfsservctl() - This is the interface for the NFS daemon.

    nice() - That commonly used and known command "nice" is another syscall.

    uname() - Here is yet another syscall that is sometimes used by the user in a command-line or script.

    open() - This syscall opens files.

    NOTE: Sometimes, the calling process is referred to as a local process and the other processes are remote. For instance, if both Firefox and Thunderbird are running on the same machine, Firefox refers to Thunderbird as a remote process as does Thunderbird to Firefox. Each process views themselves as local.

    pause() - This kernel call makes the calling process pause until one of two events take place. These two events are the death of the process (like a kill signal) or receiving a signal.

    pciconfig_iobase() - This call is used to get information about IO regions on memory.

    perf_event_open() - The system's performance is monitored when this syscall is executed.

    personality() - This syscall creates the process's execution domain. In computing, a personality is the way an executable behaves. This refers to the different system calls and application binary interfaces (ABI).

    perfmonctl() - This kernel call is the interface for the performance monitoring unit (PMU) of IA-64 CPUs.

    pipe() - This kernel call makes a pipe (|) which is a form of interprocess communication. This sends data from one process to another, and data does not go to the sender.

    pivot_root() - The root filesystem can be changed using this system call. pivot_root() is commonly used to change the root from initrd.

    poll() - This syscall watches file descriptors for ones that are ready for IO operations.

    pread() - With a given offset, pread() reads a file descriptor (fd).

    pwrite() - With a given offset, pwrite() writes to a file descriptor (fd).

    preadv() - This system call can read a file descriptor and fill many buffers. preadv() is like pread() and readv() combined.

    prlimit() - This is getrlimit() and setrlimit() combined into one syscall, so this one call gets and sets a process's resource limits.

    process_vm_readv() - This kernel call gets data from a specified process (by pid) and gives it to the calling process.

    process_vm_writev() - The calling process uses this syscall to send data to a remote process.

    pselect() - This is like poll(), watching for many file descriptors for one to be free for IO operations.

    ptrace() - A process can control and monitor another process (if permissions permit). The calling process is called the tracer and the process being monitored is called the tracee.

    pwritev() - This syscall has both the features of writev() and pwrite().

    query_module() - The information about a module can be received with this syscall.

    quotactl() - Disk quotas are managed with this syscall.

    read() - This system call gets data byte-by-byte from the specified file descriptor and places them in the buffer.

    readahead() - Files are placed in the page cache by this syscall.

    readlink() - Gets the full real pathname of the file the link points towards.

    reboot() - Obviously, this syscall reboots the system. When CAD is used (Ctrl+Alt+Del), this kernel call is executed.

    Further Reading

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    Last edited: Jun 23, 2015

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