diff options
Diffstat (limited to 'arch/x86/kernel/ioport.c')
| -rw-r--r-- | arch/x86/kernel/ioport.c | 215 |
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(¤t->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 = ¤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)); + 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 = ¤t->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 |