summaryrefslogtreecommitdiffstats
path: root/arch/x86/kernel/ioport.c
diff options
context:
space:
mode:
Diffstat (limited to 'arch/x86/kernel/ioport.c')
-rw-r--r--arch/x86/kernel/ioport.c215
1 files changed, 215 insertions, 0 deletions
diff --git a/arch/x86/kernel/ioport.c b/arch/x86/kernel/ioport.c
new file mode 100644
index 0000000000..e2fab3ceb0
--- /dev/null
+++ b/arch/x86/kernel/ioport.c
@@ -0,0 +1,215 @@
+// 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>
+#include <asm/syscalls.h>
+
+#ifdef CONFIG_X86_IOPL_IOPERM
+
+static atomic64_t io_bitmap_sequence;
+
+void io_bitmap_share(struct task_struct *tsk)
+{
+ /* Can be NULL when current->thread.iopl_emul == 3 */
+ if (current->thread.io_bitmap) {
+ /*
+ * Take a refcount on current's bitmap. It can be used by
+ * both tasks as long as none of them changes the bitmap.
+ */
+ refcount_inc(&current->thread.io_bitmap->refcnt);
+ tsk->thread.io_bitmap = current->thread.io_bitmap;
+ }
+ set_tsk_thread_flag(tsk, TIF_IO_BITMAP);
+}
+
+static void task_update_io_bitmap(struct task_struct *tsk)
+{
+ struct thread_struct *t = &tsk->thread;
+
+ if (t->iopl_emul == 3 || t->io_bitmap) {
+ /* TSS update is handled on exit to user space */
+ set_tsk_thread_flag(tsk, TIF_IO_BITMAP);
+ } else {
+ clear_tsk_thread_flag(tsk, TIF_IO_BITMAP);
+ /* Invalidate TSS */
+ preempt_disable();
+ tss_update_io_bitmap();
+ preempt_enable();
+ }
+}
+
+void io_bitmap_exit(struct task_struct *tsk)
+{
+ struct io_bitmap *iobm = tsk->thread.io_bitmap;
+
+ tsk->thread.io_bitmap = NULL;
+ task_update_io_bitmap(tsk);
+ if (iobm && refcount_dec_and_test(&iobm->refcnt))
+ kfree(iobm);
+}
+
+/*
+ * 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 = &current->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));
+ refcount_set(&iobm->refcnt, 1);
+ }
+
+ /*
+ * If the bitmap is not shared, then nothing can take a refcount as
+ * current can obviously not fork at the same time. If it's shared
+ * duplicate it and drop the refcount on the original one.
+ */
+ if (refcount_read(&iobm->refcnt) > 1) {
+ iobm = kmemdup(iobm, sizeof(*iobm), GFP_KERNEL);
+ if (!iobm)
+ return -ENOMEM;
+ refcount_set(&iobm->refcnt, 1);
+ io_bitmap_exit(current);
+ }
+
+ /*
+ * Store the bitmap pointer (might be the same if the task already
+ * head one). Must be done here so freeing the bitmap when all
+ * permissions are dropped has the pointer set up.
+ */
+ t->io_bitmap = iobm;
+ /* Mark it active for context switching and exit to user mode */
+ set_thread_flag(TIF_IO_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 = UINT_MAX;
+ for (i = 0; i < IO_BITMAP_LONGS; i++) {
+ if (iobm->bitmap[i] != ~0UL)
+ max_long = i;
+ }
+ /* All permissions dropped? */
+ if (max_long == UINT_MAX) {
+ io_bitmap_exit(current);
+ return 0;
+ }
+
+ iobm->max = (max_long + 1) * sizeof(unsigned long);
+
+ /*
+ * Update the sequence number to force a TSS update on return to
+ * user mode.
+ */
+ iobm->sequence = atomic64_add_return(1, &io_bitmap_sequence);
+
+ return 0;
+}
+
+SYSCALL_DEFINE3(ioperm, unsigned long, from, unsigned long, num, int, turn_on)
+{
+ return ksys_ioperm(from, num, turn_on);
+}
+
+/*
+ * The sys_iopl functionality depends on the level argument, which if
+ * granted for the task is used to enable access to all 65536 I/O ports.
+ *
+ * This does not use the IOPL mechanism provided by the CPU as that would
+ * also allow the user space task to use the CLI/STI instructions.
+ *
+ * Disabling interrupts in a user space task is dangerous as it might lock
+ * up the machine and the semantics vs. syscalls and exceptions is
+ * undefined.
+ *
+ * Setting IOPL to level 0-2 is disabling I/O permissions. Level 3
+ * 3 enables them.
+ *
+ * IOPL is strictly per thread and inherited on fork.
+ */
+SYSCALL_DEFINE1(iopl, unsigned int, level)
+{
+ struct thread_struct *t = &current->thread;
+ unsigned int old;
+
+ if (level > 3)
+ return -EINVAL;
+
+ old = t->iopl_emul;
+
+ /* No point in going further if nothing changes */
+ if (level == old)
+ return 0;
+
+ /* Trying to gain more privileges? */
+ if (level > old) {
+ if (!capable(CAP_SYS_RAWIO) ||
+ security_locked_down(LOCKDOWN_IOPORT))
+ return -EPERM;
+ }
+
+ t->iopl_emul = level;
+ task_update_io_bitmap(current);
+
+ return 0;
+}
+
+#else /* CONFIG_X86_IOPL_IOPERM */
+
+long ksys_ioperm(unsigned long from, unsigned long num, int turn_on)
+{
+ return -ENOSYS;
+}
+SYSCALL_DEFINE3(ioperm, unsigned long, from, unsigned long, num, int, turn_on)
+{
+ return -ENOSYS;
+}
+
+SYSCALL_DEFINE1(iopl, unsigned int, level)
+{
+ return -ENOSYS;
+}
+#endif