diff options
| author | Andy Lutomirski <luto@amacapital.net> | 2014-10-29 22:33:46 +0100 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2014-11-03 21:44:57 +0100 |
| commit | 95c46b56922409ed8838b3b420b11cfebb8c6c88 (patch) | |
| tree | 3bfa61cbda840ea6bea3bab7e39b3acef9d2319d | |
| parent | x86_64, vsyscall: Turn vsyscalls all the way off when vsyscall==none (diff) | |
| download | linux-95c46b56922409ed8838b3b420b11cfebb8c6c88.tar.xz linux-95c46b56922409ed8838b3b420b11cfebb8c6c88.zip | |
x86_64, vsyscall: Rewrite comment and clean up headers in vsyscall code
vsyscall_64.c is just vsyscall emulation. Tidy it up accordingly.
[ tglx: Preserved the original copyright notices ]
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Link: http://lkml.kernel.org/r/9c448d5643d0fdb618f8cde9a54c21d2bcd486ce.1414618407.git.luto@amacapital.net
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
| -rw-r--r-- | arch/x86/kernel/vsyscall_64.c | 50 |
1 files changed, 18 insertions, 32 deletions
diff --git a/arch/x86/kernel/vsyscall_64.c b/arch/x86/kernel/vsyscall_64.c index 2d912629c96e..7d9eb4bc10ac 100644 --- a/arch/x86/kernel/vsyscall_64.c +++ b/arch/x86/kernel/vsyscall_64.c @@ -1,52 +1,38 @@ /* + * Copyright (c) 2012-2014 Andy Lutomirski <luto@amacapital.net> + * + * Based on the original implementation which is: * Copyright (C) 2001 Andrea Arcangeli <andrea@suse.de> SuSE * Copyright 2003 Andi Kleen, SuSE Labs. * - * [ NOTE: this mechanism is now deprecated in favor of the vDSO. ] + * Parts of the original code have been moved to arch/x86/vdso/vma.c + * + * This file implements vsyscall emulation. vsyscalls are a legacy ABI: + * Userspace can request certain kernel services by calling fixed + * addresses. This concept is problematic: * - * Thanks to hpa@transmeta.com for some useful hint. - * Special thanks to Ingo Molnar for his early experience with - * a different vsyscall implementation for Linux/IA32 and for the name. + * - It interferes with ASLR. + * - It's awkward to write code that lives in kernel addresses but is + * callable by userspace at fixed addresses. + * - The whole concept is impossible for 32-bit compat userspace. + * - UML cannot easily virtualize a vsyscall. * - * vsyscall 1 is located at -10Mbyte, vsyscall 2 is located - * at virtual address -10Mbyte+1024bytes etc... There are at max 4 - * vsyscalls. One vsyscall can reserve more than 1 slot to avoid - * jumping out of line if necessary. We cannot add more with this - * mechanism because older kernels won't return -ENOSYS. + * As of mid-2014, I believe that there is no new userspace code that + * will use a vsyscall if the vDSO is present. I hope that there will + * soon be no new userspace code that will ever use a vsyscall. * - * Note: the concept clashes with user mode linux. UML users should - * use the vDSO. + * The code in this file emulates vsyscalls when notified of a page + * fault to a vsyscall address. */ -#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt - -#include <linux/time.h> -#include <linux/init.h> #include <linux/kernel.h> #include <linux/timer.h> -#include <linux/seqlock.h> -#include <linux/jiffies.h> -#include <linux/sysctl.h> -#include <linux/topology.h> -#include <linux/timekeeper_internal.h> -#include <linux/getcpu.h> -#include <linux/cpu.h> -#include <linux/smp.h> -#include <linux/notifier.h> #include <linux/syscalls.h> #include <linux/ratelimit.h> #include <asm/vsyscall.h> -#include <asm/pgtable.h> -#include <asm/compat.h> -#include <asm/page.h> #include <asm/unistd.h> #include <asm/fixmap.h> -#include <asm/errno.h> -#include <asm/io.h> -#include <asm/segment.h> -#include <asm/desc.h> -#include <asm/topology.h> #include <asm/traps.h> #define CREATE_TRACE_POINTS |