diff options
Diffstat (limited to 'arch/x86/kernel/ioport.c')
| -rw-r--r-- | arch/x86/kernel/ioport.c | 138 |
1 files changed, 138 insertions, 0 deletions
diff --git a/arch/x86/kernel/ioport.c b/arch/x86/kernel/ioport.c new file mode 100644 index 000000000..0fe1c8782 --- /dev/null +++ b/arch/x86/kernel/ioport.c @@ -0,0 +1,138 @@ +// 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/sched.h> +#include <linux/sched/task_stack.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/stddef.h> +#include <linux/slab.h> +#include <linux/thread_info.h> +#include <linux/syscalls.h> +#include <linux/bitmap.h> +#include <asm/syscalls.h> +#include <asm/desc.h> + +/* + * 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; + struct tss_struct *tss; + unsigned int i, max_long, bytes, bytes_updated; + + 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) { + unsigned long *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); + + /* + * Now that we have an IO bitmap, we need our TSS limit to be + * correct. It's fine if we are preempted after doing this: + * with TIF_IO_BITMAP set, context switches will keep our TSS + * limit correct. + */ + preempt_disable(); + refresh_tss_limit(); + preempt_enable(); + } + + /* + * 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(cpu_tss_rw, get_cpu()); + + if (turn_on) + bitmap_clear(t->io_bitmap_ptr, from, num); + else + bitmap_set(t->io_bitmap_ptr, from, num); + + /* + * 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(unsigned long); + bytes_updated = max(bytes, t->io_bitmap_max); + + t->io_bitmap_max = bytes; + + /* Update the TSS: */ + memcpy(tss->io_bitmap, t->io_bitmap_ptr, bytes_updated); + + put_cpu(); + + return 0; +} + +SYSCALL_DEFINE3(ioperm, unsigned long, from, unsigned long, num, int, turn_on) +{ + return ksys_ioperm(from, num, turn_on); +} + +/* + * 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 flags 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. + */ +SYSCALL_DEFINE1(iopl, unsigned int, level) +{ + struct pt_regs *regs = current_pt_regs(); + struct thread_struct *t = ¤t->thread; + + /* + * Careful: the IOPL bits in regs->flags are undefined under Xen PV + * and changing them has no effect. + */ + unsigned int old = t->iopl >> X86_EFLAGS_IOPL_BIT; + + if (level > 3) + return -EINVAL; + /* Trying to gain more privileges? */ + if (level > old) { + if (!capable(CAP_SYS_RAWIO)) + return -EPERM; + } + regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) | + (level << X86_EFLAGS_IOPL_BIT); + t->iopl = level << X86_EFLAGS_IOPL_BIT; + set_iopl_mask(t->iopl); + + return 0; +} |