1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * This contains the io-permission bitmap code - written by obz, with changes 4 * by Linus. 32/64 bits code unification by Miguel Botón. 5 */ 6 7 #include <linux/sched.h> 8 #include <linux/sched/task_stack.h> 9 #include <linux/kernel.h> 10 #include <linux/capability.h> 11 #include <linux/errno.h> 12 #include <linux/types.h> 13 #include <linux/ioport.h> 14 #include <linux/smp.h> 15 #include <linux/stddef.h> 16 #include <linux/slab.h> 17 #include <linux/thread_info.h> 18 #include <linux/syscalls.h> 19 #include <linux/bitmap.h> 20 #include <asm/syscalls.h> 21 #include <asm/desc.h> 22 23 /* 24 * this changes the io permissions bitmap in the current task. 25 */ 26 asmlinkage long sys_ioperm(unsigned long from, unsigned long num, int turn_on) 27 { 28 struct thread_struct *t = ¤t->thread; 29 struct tss_struct *tss; 30 unsigned int i, max_long, bytes, bytes_updated; 31 32 if ((from + num <= from) || (from + num > IO_BITMAP_BITS)) 33 return -EINVAL; 34 if (turn_on && !capable(CAP_SYS_RAWIO)) 35 return -EPERM; 36 37 /* 38 * If it's the first ioperm() call in this thread's lifetime, set the 39 * IO bitmap up. ioperm() is much less timing critical than clone(), 40 * this is why we delay this operation until now: 41 */ 42 if (!t->io_bitmap_ptr) { 43 unsigned long *bitmap = kmalloc(IO_BITMAP_BYTES, GFP_KERNEL); 44 45 if (!bitmap) 46 return -ENOMEM; 47 48 memset(bitmap, 0xff, IO_BITMAP_BYTES); 49 t->io_bitmap_ptr = bitmap; 50 set_thread_flag(TIF_IO_BITMAP); 51 52 /* 53 * Now that we have an IO bitmap, we need our TSS limit to be 54 * correct. It's fine if we are preempted after doing this: 55 * with TIF_IO_BITMAP set, context switches will keep our TSS 56 * limit correct. 57 */ 58 preempt_disable(); 59 refresh_tss_limit(); 60 preempt_enable(); 61 } 62 63 /* 64 * do it in the per-thread copy and in the TSS ... 65 * 66 * Disable preemption via get_cpu() - we must not switch away 67 * because the ->io_bitmap_max value must match the bitmap 68 * contents: 69 */ 70 tss = &per_cpu(cpu_tss_rw, get_cpu()); 71 72 if (turn_on) 73 bitmap_clear(t->io_bitmap_ptr, from, num); 74 else 75 bitmap_set(t->io_bitmap_ptr, from, num); 76 77 /* 78 * Search for a (possibly new) maximum. This is simple and stupid, 79 * to keep it obviously correct: 80 */ 81 max_long = 0; 82 for (i = 0; i < IO_BITMAP_LONGS; i++) 83 if (t->io_bitmap_ptr[i] != ~0UL) 84 max_long = i; 85 86 bytes = (max_long + 1) * sizeof(unsigned long); 87 bytes_updated = max(bytes, t->io_bitmap_max); 88 89 t->io_bitmap_max = bytes; 90 91 /* Update the TSS: */ 92 memcpy(tss->io_bitmap, t->io_bitmap_ptr, bytes_updated); 93 94 put_cpu(); 95 96 return 0; 97 } 98 99 /* 100 * sys_iopl has to be used when you want to access the IO ports 101 * beyond the 0x3ff range: to get the full 65536 ports bitmapped 102 * you'd need 8kB of bitmaps/process, which is a bit excessive. 103 * 104 * Here we just change the flags value on the stack: we allow 105 * only the super-user to do it. This depends on the stack-layout 106 * on system-call entry - see also fork() and the signal handling 107 * code. 108 */ 109 SYSCALL_DEFINE1(iopl, unsigned int, level) 110 { 111 struct pt_regs *regs = current_pt_regs(); 112 struct thread_struct *t = ¤t->thread; 113 114 /* 115 * Careful: the IOPL bits in regs->flags are undefined under Xen PV 116 * and changing them has no effect. 117 */ 118 unsigned int old = t->iopl >> X86_EFLAGS_IOPL_BIT; 119 120 if (level > 3) 121 return -EINVAL; 122 /* Trying to gain more privileges? */ 123 if (level > old) { 124 if (!capable(CAP_SYS_RAWIO)) 125 return -EPERM; 126 } 127 regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) | 128 (level << X86_EFLAGS_IOPL_BIT); 129 t->iopl = level << X86_EFLAGS_IOPL_BIT; 130 set_iopl_mask(t->iopl); 131 132 return 0; 133 } 134