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Since Linux v3.2, vsyscalls have been deprecated and slow. From v3.2 on, Linux had three vsyscall modes: "native", "emulate", and "none". "emulate" is the default. All known user programs work correctly in emulate mode, but vsyscalls turn into page faults and are emulated. This is very slow. In "native" mode, the vsyscall page is easily usable as an exploit gadget, but vsyscalls are a bit faster -- they turn into normal syscalls. (This is in contrast to vDSO functions, which can be much faster than syscalls.) In "none" mode, there are no vsyscalls. For all practical purposes, "native" was really just a chicken bit in case something went wrong with the emulation. It's been over six years, and nothing has gone wrong. Delete it. Signed-off-by: Andy Lutomirski <luto@kernel.org> Acked-by: Kees Cook <keescook@chromium.org> Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Dominik Brodowski <linux@dominikbrodowski.net> Cc: Kernel Hardening <kernel-hardening@lists.openwall.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/519fee5268faea09ae550776ce969fa6e88668b0.1520449896.git.luto@kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.