/* * linux/arch/i386/kernel/ioport.c * * This contains the io-permission bitmap code - written by obz, with changes * by Linus. */ #include <linux/sched.h> #include <linux/kernel.h> #include <linux/capability.h> #include <linux/errno.h> #include <linux/types.h> #include <linux/ioport.h> #include <linux/smp.h> #include <linux/smp_lock.h> #include <linux/stddef.h> #include <linux/slab.h> #include <linux/thread_info.h> #include <linux/syscalls.h> /* Set EXTENT bits starting at BASE in BITMAP to value TURN_ON. */ static void set_bitmap(unsigned long *bitmap, unsigned int base, unsigned int extent, int new_value) { unsigned long mask; unsigned long *bitmap_base = bitmap + (base / BITS_PER_LONG); unsigned int low_index = base & (BITS_PER_LONG-1); int length = low_index + extent; if (low_index != 0) { mask = (~0UL << low_index); if (length < BITS_PER_LONG) mask &= ~(~0UL << length); if (new_value) *bitmap_base++ |= mask; else *bitmap_base++ &= ~mask; length -= BITS_PER_LONG; } mask = (new_value ? ~0UL : 0UL); while (length >= BITS_PER_LONG) { *bitmap_base++ = mask; length -= BITS_PER_LONG; } if (length > 0) { mask = ~(~0UL << length); if (new_value) *bitmap_base++ |= mask; else *bitmap_base++ &= ~mask; } } /* * this changes the io permissions bitmap in the current task. */ asmlinkage long sys_ioperm(unsigned long from, unsigned long num, int turn_on) { unsigned long i, max_long, bytes, bytes_updated; struct thread_struct * t = ¤t->thread; struct tss_struct * tss; unsigned long *bitmap; if ((from + num <= from) || (from + num > IO_BITMAP_BITS)) return -EINVAL; if (turn_on && !capable(CAP_SYS_RAWIO)) 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: */ if (!t->io_bitmap_ptr) { bitmap = kmalloc(IO_BITMAP_BYTES, GFP_KERNEL); if (!bitmap) return -ENOMEM; memset(bitmap, 0xff, IO_BITMAP_BYTES); t->io_bitmap_ptr = bitmap; set_thread_flag(TIF_IO_BITMAP); } /* * do it in the per-thread copy and in the TSS ... * * Disable preemption via get_cpu() - we must not switch away * because the ->io_bitmap_max value must match the bitmap * contents: */ tss = &per_cpu(init_tss, get_cpu()); set_bitmap(t->io_bitmap_ptr, from, num, !turn_on); /* * 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 (t->io_bitmap_ptr[i] != ~0UL) max_long = i; bytes = (max_long + 1) * sizeof(long); bytes_updated = max(bytes, t->io_bitmap_max); t->io_bitmap_max = bytes; /* * Sets the lazy trigger so that the next I/O operation will * reload the correct bitmap. * Reset the owner so that a process switch will not set * tss->io_bitmap_base to IO_BITMAP_OFFSET. */ tss->x86_tss.io_bitmap_base = INVALID_IO_BITMAP_OFFSET_LAZY; tss->io_bitmap_owner = NULL; put_cpu(); return 0; } /* * 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 eflags 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. */ asmlinkage long sys_iopl(unsigned long unused) { volatile struct pt_regs * regs = (struct pt_regs *) &unused; unsigned int level = regs->ebx; unsigned int old = (regs->eflags >> 12) & 3; struct thread_struct *t = ¤t->thread; if (level > 3) return -EINVAL; /* Trying to gain more privileges? */ if (level > old) { if (!capable(CAP_SYS_RAWIO)) return -EPERM; } t->iopl = level << 12; regs->eflags = (regs->eflags & ~X86_EFLAGS_IOPL) | t->iopl; set_iopl_mask(t->iopl); return 0; }