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// 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/capability.h>
#include <linux/security.h>
#include <linux/syscalls.h>
#include <linux/bitmap.h>
#include <linux/ioport.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <asm/io_bitmap.h>
#include <asm/desc.h>
static atomic64_t io_bitmap_sequence;
/*
* this changes the io permissions bitmap in the current task.
*/
long ksys_ioperm(unsigned long from, unsigned long num, int turn_on)
{
struct thread_struct *t = ¤t->thread;
unsigned int i, max_long;
struct io_bitmap *iobm;
if ((from + num <= from) || (from + num > IO_BITMAP_BITS))
return -EINVAL;
if (turn_on && (!capable(CAP_SYS_RAWIO) ||
security_locked_down(LOCKDOWN_IOPORT)))
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:
*/
iobm = t->io_bitmap;
if (!iobm) {
/* No point to allocate a bitmap just to clear permissions */
if (!turn_on)
return 0;
iobm = kmalloc(sizeof(*iobm), GFP_KERNEL);
if (!iobm)
return -ENOMEM;
memset(iobm->bitmap, 0xff, sizeof(iobm->bitmap));
}
/*
* Update the tasks bitmap. The update of the TSS bitmap happens on
* exit to user mode. So this needs no protection.
*/
if (turn_on)
bitmap_clear(iobm->bitmap, from, num);
else
bitmap_set(iobm->bitmap, 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 (iobm->bitmap[i] != ~0UL)
max_long = i;
}
iobm->max = (max_long + 1) * sizeof(unsigned long);
/* Update the sequence number to force an update in switch_to() */
iobm->sequence = atomic64_add_return(1, &io_bitmap_sequence);
/*
* Store the bitmap pointer (might be the same if the task already
* head one). Set the TIF flag, just in case this is the first
* invocation.
*/
t->io_bitmap = iobm;
set_thread_flag(TIF_IO_BITMAP);
return 0;
}
SYSCALL_DEFINE3(ioperm, unsigned long, from, unsigned long, num, int, turn_on)
{
return ksys_ioperm(from, num, turn_on);
}
/*
* 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 = ¤t->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) ||
security_locked_down(LOCKDOWN_IOPORT))
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;
}
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