Release 4.14 arch/x86/kernel/ioport.c

// SPDX-License-Identifier: GPL-2.0
/*
 * This contains the io-permission bitmap code - written by obz, with changes
 * by Linus. 32/64 bits code unification by Miguel Botón.
 */

#include <linux/sched.h>
#include <linux/sched/task_stack.h>
#include <linux/kernel.h>
#include <linux/capability.h>
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/ioport.h>
#include <linux/smp.h>
#include <linux/stddef.h>
#include <linux/slab.h>
#include <linux/thread_info.h>
#include <linux/syscalls.h>
#include <linux/bitmap.h>
#include <asm/syscalls.h>
#include <asm/desc.h>

/*
 * this changes the io permissions bitmap in the current task.
 */


asmlinkage long sys_ioperm(unsigned long from, unsigned long num, int turn_on)
{
	struct thread_struct *t = &current->thread;
	struct tss_struct *tss;
	unsigned int i, max_long, bytes, bytes_updated;

	if ((from + num <= from) || (from + num > IO_BITMAP_BITS))
		return -EINVAL;
	if (turn_on && !capable(CAP_SYS_RAWIO))
		return -EPERM;

	/*
         * If it's the first ioperm() call in this thread's lifetime, set the
         * IO bitmap up. ioperm() is much less timing critical than clone(),
         * this is why we delay this operation until now:
         */
	if (!t->io_bitmap_ptr) {
		unsigned long *bitmap = kmalloc(IO_BITMAP_BYTES, GFP_KERNEL);

		if (!bitmap)
			return -ENOMEM;

		memset(bitmap, 0xff, IO_BITMAP_BYTES);
		t->io_bitmap_ptr = bitmap;
		set_thread_flag(TIF_IO_BITMAP);

		/*
                 * Now that we have an IO bitmap, we need our TSS limit to be
                 * correct.  It's fine if we are preempted after doing this:
                 * with TIF_IO_BITMAP set, context switches will keep our TSS
                 * limit correct.
                 */
		preempt_disable();
		refresh_tss_limit();
		preempt_enable();
	}

	/*
         * do it in the per-thread copy and in the TSS ...
         *
         * Disable preemption via get_cpu() - we must not switch away
         * because the ->io_bitmap_max value must match the bitmap
         * contents:
         */
	tss = &per_cpu(cpu_tss, get_cpu());

	if (turn_on)
		bitmap_clear(t->io_bitmap_ptr, from, num);
	else
		bitmap_set(t->io_bitmap_ptr, from, num);

	/*
         * Search for a (possibly new) maximum. This is simple and stupid,
         * to keep it obviously correct:
         */
	max_long = 0;
	for (i = 0; i < IO_BITMAP_LONGS; i++)
		if (t->io_bitmap_ptr[i] != ~0UL)
			max_long = i;

	bytes = (max_long + 1) * sizeof(unsigned long);
	bytes_updated = max(bytes, t->io_bitmap_max);

	t->io_bitmap_max = bytes;

	/* Update the TSS: */
	memcpy(tss->io_bitmap, t->io_bitmap_ptr, bytes_updated);

	put_cpu();

	return 0;
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
Linus Torvalds (pre-git)
88
33.46%
8
34.78%
Ingo Molnar
43
16.35%
1
4.35%
Miguel Botón
37
14.07%
1
4.35%
Benjamin LaHaise
17
6.46%
1
4.35%
Akinobu Mita
16
6.08%
1
4.35%
Thomas Gleixner
12
4.56%
1
4.35%
Andrew Lutomirski
11
4.18%
3
13.04%
Brian Gerst
11
4.18%
1
4.35%
Albert D. Cahalan
8
3.04%
2
8.70%
Andrew Morton
6
2.28%
1
4.35%
Stéphane Eranian
5
1.90%
1
4.35%
Shai Fultheim
5
1.90%
1
4.35%
Robert Love
4
1.52%
1
4.35%
Total
263
100.00%
23
100.00%

/*
 * sys_iopl has to be used when you want to access the IO ports
 * beyond the 0x3ff range: to get the full 65536 ports bitmapped
 * you'd need 8kB of bitmaps/process, which is a bit excessive.
 *
 * Here we just change the flags value on the stack: we allow
 * only the super-user to do it. This depends on the stack-layout
 * on system-call entry - see also fork() and the signal handling
 * code.
 */

SYSCALL_DEFINE1(iopl, unsigned int, level)
{
	struct pt_regs *regs = current_pt_regs();
	struct thread_struct *t = &current->thread;

	/*
         * Careful: the IOPL bits in regs->flags are undefined under Xen PV
         * and changing them has no effect.
         */
	unsigned int old = t->iopl >> X86_EFLAGS_IOPL_BIT;

	if (level > 3)
		return -EINVAL;
	/* Trying to gain more privileges? */
	if (level > old) {
		if (!capable(CAP_SYS_RAWIO))
			return -EPERM;
	}
	regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) |
		(level << X86_EFLAGS_IOPL_BIT);
	t->iopl = level << X86_EFLAGS_IOPL_BIT;
	set_iopl_mask(t->iopl);

	return 0;
}
Overall Contributors
Person
Tokens
Prop
Commits
CommitProp
Linus Torvalds (pre-git)
149
35.56%
11
28.95%
Miguel Botón
53
12.65%
1
2.63%
Ingo Molnar
46
10.98%
2
5.26%
Andrew Lutomirski
27
6.44%
4
10.53%
Brian Gerst
22
5.25%
2
5.26%
Benjamin LaHaise
20
4.77%
1
2.63%
Akinobu Mita
20
4.77%
1
2.63%
Al Viro
13
3.10%
1
2.63%
Thomas Gleixner
12
2.86%
1
2.63%
Chris Wright
10
2.39%
1
2.63%
Albert D. Cahalan
8
1.91%
2
5.26%
Andrew Morton
6
1.43%
1
2.63%
Shai Fultheim
5
1.19%
1
2.63%
Zachary Amsden
5
1.19%
1
2.63%
Stéphane Eranian
5
1.19%
1
2.63%
Linus Torvalds
4
0.95%
1
2.63%
Robert Love
4
0.95%
1
2.63%
Randy Dunlap
3
0.72%
1
2.63%
Adrian Bunk
3
0.72%
1
2.63%
Jaswinder Singh Rajput
2
0.48%
1
2.63%
H. Peter Anvin
1
0.24%
1
2.63%
Greg Kroah-Hartman
1
0.24%
1
2.63%
Total
419
100.00%
38
100.00%
Directory: arch/x86/kernel

Information contained on this website is for historical information purposes only and does not indicate or represent copyright ownership.