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66f4e88cc6
Using this helper allows us to avoid the in-kernel calls to the sys_ioperm() syscall. The ksys_ prefix denotes that this function is meant as a drop-in replacement for the syscall. In particular, it uses the same calling convention as sys_ioperm(). This patch is part of a series which removes in-kernel calls to syscalls. On this basis, the syscall entry path can be streamlined. For details, see http://lkml.kernel.org/r/20180325162527.GA17492@light.dominikbrodowski.net Cc: Ingo Molnar <mingo@redhat.com> Cc: Jiri Slaby <jslaby@suse.com> Cc: x86@kernel.org Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
139 lines
3.6 KiB
C
139 lines
3.6 KiB
C
// 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/sched.h>
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#include <linux/sched/task_stack.h>
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#include <linux/kernel.h>
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#include <linux/capability.h>
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#include <linux/errno.h>
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#include <linux/types.h>
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#include <linux/ioport.h>
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#include <linux/smp.h>
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#include <linux/stddef.h>
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#include <linux/slab.h>
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#include <linux/thread_info.h>
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#include <linux/syscalls.h>
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#include <linux/bitmap.h>
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#include <asm/syscalls.h>
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#include <asm/desc.h>
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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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struct tss_struct *tss;
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unsigned int i, max_long, bytes, bytes_updated;
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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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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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if (!t->io_bitmap_ptr) {
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unsigned long *bitmap = kmalloc(IO_BITMAP_BYTES, GFP_KERNEL);
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if (!bitmap)
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return -ENOMEM;
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memset(bitmap, 0xff, IO_BITMAP_BYTES);
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t->io_bitmap_ptr = bitmap;
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set_thread_flag(TIF_IO_BITMAP);
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/*
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* Now that we have an IO bitmap, we need our TSS limit to be
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* correct. It's fine if we are preempted after doing this:
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* with TIF_IO_BITMAP set, context switches will keep our TSS
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* limit correct.
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*/
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preempt_disable();
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refresh_tss_limit();
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preempt_enable();
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}
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/*
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* do it in the per-thread copy and in the TSS ...
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*
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* Disable preemption via get_cpu() - we must not switch away
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* because the ->io_bitmap_max value must match the bitmap
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* contents:
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*/
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tss = &per_cpu(cpu_tss_rw, get_cpu());
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if (turn_on)
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bitmap_clear(t->io_bitmap_ptr, from, num);
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else
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bitmap_set(t->io_bitmap_ptr, 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 = 0;
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for (i = 0; i < IO_BITMAP_LONGS; i++)
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if (t->io_bitmap_ptr[i] != ~0UL)
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max_long = i;
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bytes = (max_long + 1) * sizeof(unsigned long);
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bytes_updated = max(bytes, t->io_bitmap_max);
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t->io_bitmap_max = bytes;
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/* Update the TSS: */
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memcpy(tss->io_bitmap, t->io_bitmap_ptr, bytes_updated);
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put_cpu();
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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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* sys_iopl has to be used when you want to access the IO ports
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* beyond the 0x3ff range: to get the full 65536 ports bitmapped
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* you'd need 8kB of bitmaps/process, which is a bit excessive.
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*
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* Here we just change the flags value on the stack: we allow
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* only the super-user to do it. This depends on the stack-layout
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* on system-call entry - see also fork() and the signal handling
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* code.
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*/
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SYSCALL_DEFINE1(iopl, unsigned int, level)
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{
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struct pt_regs *regs = current_pt_regs();
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struct thread_struct *t = ¤t->thread;
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/*
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* Careful: the IOPL bits in regs->flags are undefined under Xen PV
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* and changing them has no effect.
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*/
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unsigned int old = t->iopl >> X86_EFLAGS_IOPL_BIT;
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if (level > 3)
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return -EINVAL;
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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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return -EPERM;
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}
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regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) |
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(level << X86_EFLAGS_IOPL_BIT);
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t->iopl = level << X86_EFLAGS_IOPL_BIT;
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set_iopl_mask(t->iopl);
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return 0;
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}
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