x86, msr: Export the register-setting MSR functions via /dev/*/msr

Make it possible to access the all-register-setting/getting MSR
functions via the MSR driver.  This is implemented as an ioctl() on
the standard MSR device node.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Cc: Borislav Petkov <petkovbb@gmail.com>

1 files changed, 51 insertions, 0 deletions

diff --git a/arch/x86/kernel/msr.c b/arch/x86/kernel/msr.c
index 2cfbb4b2c422..7dd950094178 100644
--- a/arch/x86/kernel/msr.c
+++ b/arch/x86/kernel/msr.c
@@ -1,6 +1,7 @@
 /* ----------------------------------------------------------------------- *
  *
  *   Copyright 2000-2008 H. Peter Anvin - All Rights Reserved
+ *   Copyright 2009 Intel Corporation; author: H. Peter Anvin
  *
  *   This program is free software; you can redistribute it and/or modify
  *   it under the terms of the GNU General Public License as published by
@@ -121,6 +122,54 @@ static ssize_t msr_write(struct file *file, const char __user *buf,
         return bytes ? bytes : err;
 }
 
+static long msr_ioctl(struct file *file, unsigned int ioc, unsigned long arg)
+{
+        u32 __user *uregs = (u32 __user *)arg;
+        u32 regs[8];
+        int cpu = iminor(file->f_path.dentry->d_inode);
+        int err;
+
+        switch (ioc) {
+        case X86_IOC_RDMSR_REGS:
+                if (!(file->f_mode & FMODE_READ)) {
+                        err = -EBADF;
+                        break;
+                }
+                if (copy_from_user(&regs, uregs, sizeof regs)) {
+                        err = -EFAULT;
+                        break;
+                }
+                err = rdmsr_safe_regs_on_cpu(cpu, regs);
+                if (err)
+                        break;
+                if (copy_to_user(uregs, &regs, sizeof regs))
+                        err = -EFAULT;
+                break;
+
+        case X86_IOC_WRMSR_REGS:
+                if (!(file->f_mode & FMODE_WRITE)) {
+                        err = -EBADF;
+                        break;
+                }
+                if (copy_from_user(&regs, uregs, sizeof regs)) {
+                        err = -EFAULT;
+                        break;
+                }
+                err = wrmsr_safe_regs_on_cpu(cpu, regs);
+                if (err)
+                        break;
+                if (copy_to_user(uregs, &regs, sizeof regs))
+                        err = -EFAULT;
+                break;
+
+        default:
+                err = -ENOTTY;
+                break;
+        }
+
+        return err;
+}
+
 static int msr_open(struct inode *inode, struct file *file)
 {
         unsigned int cpu = iminor(file->f_path.dentry->d_inode);
@@ -151,6 +200,8 @@ static const struct file_operations msr_fops = {
         .read = msr_read,
         .write = msr_write,
         .open = msr_open,
+        .unlocked_ioctl = msr_ioctl,
+        .compat_ioctl = msr_ioctl,
 };
 
 static int __cpuinit msr_device_create(int cpu)