arno/linux-insides
1
0
Fork 0
mirror of https://github.com/0xAX/linux-insides.git synced 2024-12-22 06:38:07 +00:00
Code Issues Releases Wiki Activity

Merge pull request #506 from diekmann/patch-1

Browse Source 
Minor language improvement
This commit is contained in:
0xAX 2017-08-10 18:40:54 +06:00 committed by GitHub
commit 848436789f
1 changed files with 1 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
SysCall/syscall-3.md
View File

@ -6,7 +6,7 @@ vsyscalls and vDSO
This is the third part of the [chapter](http://0xax.gitbooks.io/linux-insides/content/SysCall/index.html) that describes system calls in the Linux kernel and we saw preparations after a system call caused by a userspace application and process of handling of a system call in the previous [part](http://0xax.gitbooks.io/linux-insides/content/SysCall/syscall-2.html). In this part we will look at two concepts that are very close to the system call concept, they are called `vsyscall` and `vdso`.
We already know what is a `system call`. This is special routine in the Linux kernel which userspace application asks to do privileged tasks, like to read or to write to a file, to open a socket and etc. As you may know, invoking a system call is an expensive operation in the Linux kernel, because the processor must interrupt the currently executing task and switch context to kernel mode, subsequently jumping again into userspace after the system call handler finishes its work. These two mechanisms - `vsyscall` and `vdso` are designed to speed up this process for certain system calls and in this part we will try to understand how these mechanisms work.
We already know what `system call`s are. They are special routines in the Linux kernel which userspace applications ask to do privileged tasks, like to read or to write to a file, to open a socket, etc. As you may know, invoking a system call is an expensive operation in the Linux kernel, because the processor must interrupt the currently executing task and switch context to kernel mode, subsequently jumping again into userspace after the system call handler finishes its work. These two mechanisms - `vsyscall` and `vdso` are designed to speed up this process for certain system calls and in this part we will try to understand how these mechanisms work.
Introduction to vsyscalls
--------------------------------------------------------------------------------