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215 lines
5.3 KiB
215 lines
5.3 KiB
// SPDX-License-Identifier: GPL-2.0 |
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/* |
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* This contains the io-permission bitmap code - written by obz, with changes |
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* by Linus. 32/64 bits code unification by Miguel Botón. |
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*/ |
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#include <linux/capability.h> |
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#include <linux/security.h> |
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#include <linux/syscalls.h> |
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#include <linux/bitmap.h> |
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#include <linux/ioport.h> |
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#include <linux/sched.h> |
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#include <linux/slab.h> |
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#include <asm/io_bitmap.h> |
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#include <asm/desc.h> |
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#include <asm/syscalls.h> |
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#ifdef CONFIG_X86_IOPL_IOPERM |
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static atomic64_t io_bitmap_sequence; |
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void io_bitmap_share(struct task_struct *tsk) |
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{ |
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/* Can be NULL when current->thread.iopl_emul == 3 */ |
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if (current->thread.io_bitmap) { |
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/* |
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* Take a refcount on current's bitmap. It can be used by |
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* both tasks as long as none of them changes the bitmap. |
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*/ |
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refcount_inc(¤t->thread.io_bitmap->refcnt); |
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tsk->thread.io_bitmap = current->thread.io_bitmap; |
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} |
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set_tsk_thread_flag(tsk, TIF_IO_BITMAP); |
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} |
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static void task_update_io_bitmap(struct task_struct *tsk) |
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{ |
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struct thread_struct *t = &tsk->thread; |
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if (t->iopl_emul == 3 || t->io_bitmap) { |
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/* TSS update is handled on exit to user space */ |
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set_tsk_thread_flag(tsk, TIF_IO_BITMAP); |
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} else { |
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clear_tsk_thread_flag(tsk, TIF_IO_BITMAP); |
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/* Invalidate TSS */ |
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preempt_disable(); |
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tss_update_io_bitmap(); |
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preempt_enable(); |
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} |
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} |
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void io_bitmap_exit(struct task_struct *tsk) |
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{ |
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struct io_bitmap *iobm = tsk->thread.io_bitmap; |
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tsk->thread.io_bitmap = NULL; |
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task_update_io_bitmap(tsk); |
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if (iobm && refcount_dec_and_test(&iobm->refcnt)) |
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kfree(iobm); |
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} |
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/* |
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* This changes the io permissions bitmap in the current task. |
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*/ |
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long ksys_ioperm(unsigned long from, unsigned long num, int turn_on) |
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{ |
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struct thread_struct *t = ¤t->thread; |
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unsigned int i, max_long; |
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struct io_bitmap *iobm; |
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if ((from + num <= from) || (from + num > IO_BITMAP_BITS)) |
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return -EINVAL; |
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if (turn_on && (!capable(CAP_SYS_RAWIO) || |
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security_locked_down(LOCKDOWN_IOPORT))) |
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return -EPERM; |
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/* |
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* If it's the first ioperm() call in this thread's lifetime, set the |
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* IO bitmap up. ioperm() is much less timing critical than clone(), |
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* this is why we delay this operation until now: |
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*/ |
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iobm = t->io_bitmap; |
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if (!iobm) { |
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/* No point to allocate a bitmap just to clear permissions */ |
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if (!turn_on) |
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return 0; |
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iobm = kmalloc(sizeof(*iobm), GFP_KERNEL); |
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if (!iobm) |
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return -ENOMEM; |
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memset(iobm->bitmap, 0xff, sizeof(iobm->bitmap)); |
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refcount_set(&iobm->refcnt, 1); |
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} |
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/* |
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* If the bitmap is not shared, then nothing can take a refcount as |
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* current can obviously not fork at the same time. If it's shared |
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* duplicate it and drop the refcount on the original one. |
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*/ |
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if (refcount_read(&iobm->refcnt) > 1) { |
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iobm = kmemdup(iobm, sizeof(*iobm), GFP_KERNEL); |
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if (!iobm) |
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return -ENOMEM; |
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refcount_set(&iobm->refcnt, 1); |
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io_bitmap_exit(current); |
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} |
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/* |
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* Store the bitmap pointer (might be the same if the task already |
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* head one). Must be done here so freeing the bitmap when all |
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* permissions are dropped has the pointer set up. |
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*/ |
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t->io_bitmap = iobm; |
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/* Mark it active for context switching and exit to user mode */ |
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set_thread_flag(TIF_IO_BITMAP); |
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/* |
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* Update the tasks bitmap. The update of the TSS bitmap happens on |
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* exit to user mode. So this needs no protection. |
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*/ |
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if (turn_on) |
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bitmap_clear(iobm->bitmap, from, num); |
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else |
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bitmap_set(iobm->bitmap, from, num); |
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/* |
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* Search for a (possibly new) maximum. This is simple and stupid, |
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* to keep it obviously correct: |
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*/ |
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max_long = UINT_MAX; |
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for (i = 0; i < IO_BITMAP_LONGS; i++) { |
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if (iobm->bitmap[i] != ~0UL) |
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max_long = i; |
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} |
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/* All permissions dropped? */ |
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if (max_long == UINT_MAX) { |
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io_bitmap_exit(current); |
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return 0; |
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} |
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iobm->max = (max_long + 1) * sizeof(unsigned long); |
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/* |
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* Update the sequence number to force a TSS update on return to |
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* user mode. |
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*/ |
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iobm->sequence = atomic64_add_return(1, &io_bitmap_sequence); |
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return 0; |
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} |
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SYSCALL_DEFINE3(ioperm, unsigned long, from, unsigned long, num, int, turn_on) |
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{ |
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return ksys_ioperm(from, num, turn_on); |
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} |
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/* |
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* The sys_iopl functionality depends on the level argument, which if |
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* granted for the task is used to enable access to all 65536 I/O ports. |
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* |
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* This does not use the IOPL mechanism provided by the CPU as that would |
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* also allow the user space task to use the CLI/STI instructions. |
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* |
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* Disabling interrupts in a user space task is dangerous as it might lock |
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* up the machine and the semantics vs. syscalls and exceptions is |
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* undefined. |
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* |
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* Setting IOPL to level 0-2 is disabling I/O permissions. Level 3 |
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* 3 enables them. |
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* |
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* IOPL is strictly per thread and inherited on fork. |
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*/ |
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SYSCALL_DEFINE1(iopl, unsigned int, level) |
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{ |
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struct thread_struct *t = ¤t->thread; |
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unsigned int old; |
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if (level > 3) |
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return -EINVAL; |
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old = t->iopl_emul; |
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/* No point in going further if nothing changes */ |
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if (level == old) |
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return 0; |
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/* Trying to gain more privileges? */ |
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if (level > old) { |
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if (!capable(CAP_SYS_RAWIO) || |
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security_locked_down(LOCKDOWN_IOPORT)) |
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return -EPERM; |
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} |
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t->iopl_emul = level; |
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task_update_io_bitmap(current); |
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return 0; |
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} |
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#else /* CONFIG_X86_IOPL_IOPERM */ |
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long ksys_ioperm(unsigned long from, unsigned long num, int turn_on) |
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{ |
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return -ENOSYS; |
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} |
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SYSCALL_DEFINE3(ioperm, unsigned long, from, unsigned long, num, int, turn_on) |
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{ |
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return -ENOSYS; |
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} |
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SYSCALL_DEFINE1(iopl, unsigned int, level) |
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{ |
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return -ENOSYS; |
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} |
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#endif
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