[PATCHv2 3/3] x86: Support compiling out userspace I/O (iopl and ioperm)

From: Josh Triplett
Date: Tue Mar 11 2014 - 17:56:52 EST

On the vast majority of modern systems, no processes will use the
userspsace I/O syscalls, iopl and ioperm. Add a new config option,
CONFIG_X86_IOPORT, to support configuring them out of the kernel
entirely. Most current systems do not run programs using these
syscalls, so X86_IOPORT does not depend on EXPERT, though it does still
default to y.

In addition to saving a significant amount of space, this also reduces
the size of several major kernel data structures, drops a bit of code
from several task-related hot paths, and reduces the attack surface of
the kernel.

All of the task-related code dealing with userspace I/O permissions now
lives in process-io.h as several new inline functions, which become
no-ops when CONFIG_X86_IOPORT.

bloat-o-meter shows a net reduction of 9223 bytes on 32-bit and 9491
bytes on 64-bit:

32-bit bloat-o-meter:
add/remove: 0/3 grow/shrink: 0/8 up/down: 0/-9223 (-9223)
function old new delta
ioperm_active 14 3 -11
init_task 888 876 -12
cpu_init 497 465 -32
exit_thread 147 75 -72
ioperm_get 100 6 -94
__switch_to_xtra 239 141 -98
sys_iopl 114 - -114
SyS_iopl 114 - -114
copy_thread 584 443 -141
sys_ioperm 343 - -343
init_tss 8576 384 -8192

64-bit bloat-o-meter:
add/remove: 0/4 grow/shrink: 0/8 up/down: 0/-9491 (-9491)
function old new delta
cpu_init 840 835 -5
ioperm_active 12 3 -9
init_task 1416 1400 -16
stub_iopl 79 - -79
exit_thread 164 84 -80
ioperm_get 101 6 -95
__switch_to_xtra 263 155 -108
sys_iopl 129 - -129
SyS_iopl 129 - -129
copy_thread 598 455 -143
sys_ioperm 442 - -442
init_tss 8896 640 -8256

Signed-off-by: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
---
v2: Rebased. Updated bloat-o-meter statistics. Changed description of
the new Kconfig system to more neutrally describe the software using
iopl and ioperm.

arch/x86/Kconfig | 10 +++++
arch/x86/include/asm/paravirt.h | 2 +
arch/x86/include/asm/paravirt_types.h | 2 +
arch/x86/include/asm/processor.h | 51 +++++++++++++++++++++----
arch/x86/include/asm/syscalls.h | 3 ++
arch/x86/kernel/Makefile | 3 +-
arch/x86/kernel/cpu/common.c | 12 +-----
arch/x86/kernel/entry_64.S | 9 +++--
arch/x86/kernel/paravirt.c | 2 +
arch/x86/kernel/process-io.h | 71 +++++++++++++++++++++++++++++++++++
arch/x86/kernel/process.c | 34 ++---------------
arch/x86/kernel/process_32.c | 13 ++-----
arch/x86/kernel/process_64.c | 2 +-
arch/x86/kernel/ptrace.c | 8 ++++
arch/x86/xen/enlighten.c | 4 ++
drivers/tty/vt/vt_ioctl.c | 2 +-
kernel/sys_ni.c | 5 +++
17 files changed, 170 insertions(+), 63 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 0af5250..6ce28fb 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -970,6 +970,16 @@ config VM86
XFree86 to initialize some video cards via BIOS. Disabling this
option saves about 6k.

+config X86_IOPORT
+ bool "iopl and ioperm system calls"
+ default y
+ ---help---
+ This option enables the iopl and ioperm system calls, which allow
+ privileged userspace processes to directly access I/O ports. This
+ is used by software that drives hardware directly from userspace
+ without using a kernel driver. Unless you intend to run such
+ software, you can safely say N here.
+
config TOSHIBA
tristate "Toshiba Laptop support"
depends on X86_32
diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index cd6e161..52d2ec8 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -299,10 +299,12 @@ static inline void write_idt_entry(gate_desc *dt, int entry, const gate_desc *g)
{
PVOP_VCALL3(pv_cpu_ops.write_idt_entry, dt, entry, g);
}
+#ifdef CONFIG_X86_IOPORT
static inline void set_iopl_mask(unsigned mask)
{
PVOP_VCALL1(pv_cpu_ops.set_iopl_mask, mask);
}
+#endif /* CONFIG_X86_IOPORT */

/* The paravirtualized I/O functions */
static inline void slow_down_io(void)
diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h
index 7549b8b..8b51bd1 100644
--- a/arch/x86/include/asm/paravirt_types.h
+++ b/arch/x86/include/asm/paravirt_types.h
@@ -142,7 +142,9 @@ struct pv_cpu_ops {

void (*load_sp0)(struct tss_struct *tss, struct thread_struct *t);

+#ifdef CONFIG_X86_IOPORT
void (*set_iopl_mask)(unsigned mask);
+#endif /* CONFIG_X86_IOPORT */

void (*wbinvd)(void);
void (*io_delay)(void);
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 7da8794..853d24c 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -256,7 +256,11 @@ struct x86_hw_tss {
/*
* IO-bitmap sizes:
*/
+#ifdef CONFIG_X86_IOPORT
#define IO_BITMAP_BITS 65536
+#else
+#define IO_BITMAP_BITS 0
+#endif
#define IO_BITMAP_BYTES (IO_BITMAP_BITS/8)
#define IO_BITMAP_LONGS (IO_BITMAP_BYTES/sizeof(long))
#define INVALID_IO_BITMAP_OFFSET 0x8000
@@ -270,6 +274,7 @@ struct tss_struct {
*/
struct x86_hw_tss x86_tss;

+#ifdef CONFIG_X86_IOPORT
/*
* The extra 1 is there because the CPU will access an
* additional byte beyond the end of the IO permission
@@ -277,6 +282,7 @@ struct tss_struct {
* be within the limit.
*/
unsigned long io_bitmap[IO_BITMAP_LONGS + 1];
+#endif /* CONFIG_X86_IOPORT */

/*
* .. and then another 0x100 bytes for the emergency kernel stack:
@@ -287,6 +293,24 @@ struct tss_struct {

DECLARE_PER_CPU_SHARED_ALIGNED(struct tss_struct, init_tss);

+static inline void init_tss_io(struct tss_struct *t)
+{
+#ifdef CONFIG_X86_IOPORT
+ int i;
+
+ t->x86_tss.io_bitmap_base = offsetof(struct tss_struct, io_bitmap);
+
+ /*
+ * <= is required because the CPU will access up to
+ * 8 bits beyond the end of the IO permission bitmap.
+ */
+ for (i = 0; i <= IO_BITMAP_LONGS; i++)
+ t->io_bitmap[i] = ~0UL;
+#else
+ t->x86_tss.io_bitmap_base = INVALID_IO_BITMAP_OFFSET;
+#endif
+}
+
/*
* Save the original ist values for checking stack pointers during debugging
*/
@@ -502,11 +526,13 @@ struct thread_struct {
unsigned int saved_fs;
unsigned int saved_gs;
#endif
+#ifdef CONFIG_X86_IOPORT
/* IO permissions: */
unsigned long *io_bitmap_ptr;
unsigned long iopl;
/* Max allowed port in the bitmap, in bytes: */
unsigned io_bitmap_max;
+#endif /* CONFIG_X86_IOPORT */
/*
* fpu_counter contains the number of consecutive context switches
* that the FPU is used. If this is over a threshold, the lazy fpu
@@ -518,6 +544,7 @@ struct thread_struct {
unsigned char fpu_counter;
};

+#ifdef CONFIG_X86_IOPORT
/*
* Set IOPL bits in EFLAGS from given mask
*/
@@ -536,6 +563,7 @@ static inline void native_set_iopl_mask(unsigned mask)
: "i" (~X86_EFLAGS_IOPL), "r" (mask));
#endif
}
+#endif /* CONFIG_X86_IOPORT */

static inline void
native_load_sp0(struct tss_struct *tss, struct thread_struct *thread)
@@ -832,12 +860,8 @@ static inline void spin_lock_prefetch(const void *x)
#define STACK_TOP TASK_SIZE
#define STACK_TOP_MAX STACK_TOP

-#define INIT_THREAD { \
- .sp0 = sizeof(init_stack) + (long)&init_stack, \
- .vm86_info = NULL, \
- .sysenter_cs = __KERNEL_CS, \
- .io_bitmap_ptr = NULL, \
-}
+#ifdef CONFIG_X86_IOPORT
+#define INIT_THREAD_IO .io_bitmap_ptr = NULL,

/*
* Note that the .io_bitmap member must be extra-big. This is because
@@ -845,6 +869,19 @@ static inline void spin_lock_prefetch(const void *x)
* permission bitmap. The extra byte must be all 1 bits, and must
* be within the limit.
*/
+#define INIT_TSS_IO .io_bitmap = { [0 ... IO_BITMAP_LONGS] = ~0 },
+#else
+#define INIT_THREAD_IO
+#define INIT_TSS_IO
+#endif
+
+#define INIT_THREAD { \
+ .sp0 = sizeof(init_stack) + (long)&init_stack, \
+ .vm86_info = NULL, \
+ .sysenter_cs = __KERNEL_CS, \
+ INIT_THREAD_IO \
+}
+
#define INIT_TSS { \
.x86_tss = { \
.sp0 = sizeof(init_stack) + (long)&init_stack, \
@@ -852,7 +889,7 @@ static inline void spin_lock_prefetch(const void *x)
.ss1 = __KERNEL_CS, \
.io_bitmap_base = INVALID_IO_BITMAP_OFFSET, \
}, \
- .io_bitmap = { [0 ... IO_BITMAP_LONGS] = ~0 }, \
+ INIT_TSS_IO \
}

extern unsigned long thread_saved_pc(struct task_struct *tsk);
diff --git a/arch/x86/include/asm/syscalls.h b/arch/x86/include/asm/syscalls.h
index 592a6a6..4db79ea 100644
--- a/arch/x86/include/asm/syscalls.h
+++ b/arch/x86/include/asm/syscalls.h
@@ -16,9 +16,12 @@
#include <linux/types.h>

/* Common in X86_32 and X86_64 */
+
+#ifdef CONFIG_X86_IOPORT
/* kernel/ioport.c */
asmlinkage long sys_ioperm(unsigned long, unsigned long, int);
asmlinkage long sys_iopl(unsigned int);
+#endif /* CONFIG_X86_IOPORT */

/* kernel/ldt.c */
asmlinkage int sys_modify_ldt(int, void __user *, unsigned long);
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index cb648c8..0d84b07 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -20,7 +20,8 @@ CFLAGS_irq.o := -I$(src)/../include/asm/trace

obj-y := process_$(BITS).o signal.o entry_$(BITS).o
obj-y += traps.o irq.o irq_$(BITS).o dumpstack_$(BITS).o
-obj-y += time.o ioport.o ldt.o dumpstack.o nmi.o
+obj-y += time.o ldt.o dumpstack.o nmi.o
+obj-$(CONFIG_X86_IOPORT) += ioport.o
obj-y += setup.o x86_init.o i8259.o irqinit.o jump_label.o
obj-$(CONFIG_IRQ_WORK) += irq_work.o
obj-y += probe_roms.o
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 8e28bf2..de79215 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1236,7 +1236,6 @@ void cpu_init(void)
struct tss_struct *t;
unsigned long v;
int cpu;
- int i;

/*
* Load microcode on this cpu if a valid microcode is available.
@@ -1298,14 +1297,7 @@ void cpu_init(void)
}
}

- t->x86_tss.io_bitmap_base = offsetof(struct tss_struct, io_bitmap);
-
- /*
- * <= is required because the CPU will access up to
- * 8 bits beyond the end of the IO permission bitmap.
- */
- for (i = 0; i <= IO_BITMAP_LONGS; i++)
- t->io_bitmap[i] = ~0UL;
+ init_tss_io(t);

atomic_inc(&init_mm.mm_count);
me->active_mm = &init_mm;
@@ -1364,7 +1356,7 @@ void cpu_init(void)
load_TR_desc();
load_LDT(&init_mm.context);

- t->x86_tss.io_bitmap_base = offsetof(struct tss_struct, io_bitmap);
+ init_tss_io(t);

#ifdef CONFIG_DOUBLEFAULT
/* Set up doublefault TSS pointer in the GDT */
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 1e96c36..d2d873a 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -829,6 +829,11 @@ ENTRY(stub_\func)
END(stub_\func)
.endm

+ FORK_LIKE clone
+ FORK_LIKE fork
+ FORK_LIKE vfork
+
+#ifdef CONFIG_X86_IOPORT
.macro FIXED_FRAME label,func
ENTRY(\label)
CFI_STARTPROC
@@ -841,10 +846,8 @@ ENTRY(\label)
END(\label)
.endm

- FORK_LIKE clone
- FORK_LIKE fork
- FORK_LIKE vfork
FIXED_FRAME stub_iopl, sys_iopl
+#endif /* CONFIG_X86_IOPORT */

ENTRY(ptregscall_common)
DEFAULT_FRAME 1 8 /* offset 8: return address */
diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
index 1b10af8..46da3d9 100644
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -382,7 +382,9 @@ __visible struct pv_cpu_ops pv_cpu_ops = {
.iret = native_iret,
.swapgs = native_swapgs,

+#ifdef CONFIG_X86_IOPORT
.set_iopl_mask = native_set_iopl_mask,
+#endif /* CONFIG_X86_IOPORT */
.io_delay = native_io_delay,

.start_context_switch = paravirt_nop,
diff --git a/arch/x86/kernel/process-io.h b/arch/x86/kernel/process-io.h
index d884444..3e773fa 100644
--- a/arch/x86/kernel/process-io.h
+++ b/arch/x86/kernel/process-io.h
@@ -1,9 +1,17 @@
#ifndef _X86_KERNEL_PROCESS_IO_H
#define _X86_KERNEL_PROCESS_IO_H

+static inline void clear_thread_io_bitmap(struct task_struct *p)
+{
+#ifdef CONFIG_X86_IOPORT
+ p->thread.io_bitmap_ptr = NULL;
+#endif /* CONFIG_X86_IOPORT */
+}
+
static inline int copy_io_bitmap(struct task_struct *me,
struct task_struct *p)
{
+#ifdef CONFIG_X86_IOPORT
if (unlikely(test_tsk_thread_flag(me, TIF_IO_BITMAP))) {
p->thread.io_bitmap_ptr = kmemdup(me->thread.io_bitmap_ptr,
IO_BITMAP_BYTES, GFP_KERNEL);
@@ -15,8 +23,71 @@ static inline int copy_io_bitmap(struct task_struct *me,
} else {
p->thread.io_bitmap_ptr = NULL;
}
+#endif /* CONFIG_X86_IOPORT */

return 0;
}

+static inline void exit_thread_io(struct task_struct *me)
+{
+#ifdef CONFIG_X86_IOPORT
+ struct thread_struct *t = &me->thread;
+ unsigned long *bp = t->io_bitmap_ptr;
+
+ if (bp) {
+ struct tss_struct *tss = &per_cpu(init_tss, get_cpu());
+
+ t->io_bitmap_ptr = NULL;
+ clear_thread_flag(TIF_IO_BITMAP);
+ /*
+ * Careful, clear this in the TSS too:
+ */
+ memset(tss->io_bitmap, 0xff, t->io_bitmap_max);
+ t->io_bitmap_max = 0;
+ put_cpu();
+ kfree(bp);
+ }
+#endif /* CONFIG_X86_IOPORT */
+}
+
+static inline void switch_iopl_mask(struct thread_struct *prev,
+ struct thread_struct *next)
+{
+#ifdef CONFIG_X86_IOPORT
+ /*
+ * Restore IOPL if needed. In normal use, the flags restore
+ * in the switch assembly will handle this. But if the kernel
+ * is running virtualized at a non-zero CPL, the popf will
+ * not restore flags, so it must be done in a separate step.
+ */
+ if (get_kernel_rpl() && unlikely(prev->iopl != next->iopl))
+ set_iopl_mask(next->iopl);
+#endif /* CONFIG_X86_IOPORT */
+}
+
+static inline void switch_io_bitmap(struct tss_struct *tss,
+ struct task_struct *prev_p,
+ struct task_struct *next_p)
+{
+#ifdef CONFIG_X86_IOPORT
+ struct thread_struct *prev, *next;
+ prev = &prev_p->thread;
+ next = &next_p->thread;
+
+ if (test_tsk_thread_flag(next_p, TIF_IO_BITMAP)) {
+ /*
+ * Copy the relevant range of the IO bitmap.
+ * Normally this is 128 bytes or less:
+ */
+ memcpy(tss->io_bitmap, next->io_bitmap_ptr,
+ max(prev->io_bitmap_max, next->io_bitmap_max));
+ } else if (test_tsk_thread_flag(prev_p, TIF_IO_BITMAP)) {
+ /*
+ * Clear any possible leftover bits:
+ */
+ memset(tss->io_bitmap, 0xff, prev->io_bitmap_max);
+ }
+#endif /* CONFIG_X86_IOPORT */
+}
+
#endif /* _X86_KERNEL_PROCESS_IO_H */
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 3fb8d95..29c0693 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -29,6 +29,8 @@
#include <asm/debugreg.h>
#include <asm/nmi.h>

+#include "process-io.h"
+
/*
* per-CPU TSS segments. Threads are completely 'soft' on Linux,
* no more per-task TSS's. The TSS size is kept cacheline-aligned
@@ -101,23 +103,7 @@ void arch_task_cache_init(void)
void exit_thread(void)
{
struct task_struct *me = current;
- struct thread_struct *t = &me->thread;
- unsigned long *bp = t->io_bitmap_ptr;
-
- if (bp) {
- struct tss_struct *tss = &per_cpu(init_tss, get_cpu());
-
- t->io_bitmap_ptr = NULL;
- clear_thread_flag(TIF_IO_BITMAP);
- /*
- * Careful, clear this in the TSS too:
- */
- memset(tss->io_bitmap, 0xff, t->io_bitmap_max);
- t->io_bitmap_max = 0;
- put_cpu();
- kfree(bp);
- }
-
+ exit_thread_io(me);
drop_fpu(me);
}

@@ -222,19 +208,7 @@ void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p,
hard_enable_TSC();
}

- if (test_tsk_thread_flag(next_p, TIF_IO_BITMAP)) {
- /*
- * Copy the relevant range of the IO bitmap.
- * Normally this is 128 bytes or less:
- */
- memcpy(tss->io_bitmap, next->io_bitmap_ptr,
- max(prev->io_bitmap_max, next->io_bitmap_max));
- } else if (test_tsk_thread_flag(prev_p, TIF_IO_BITMAP)) {
- /*
- * Clear any possible leftover bits:
- */
- memset(tss->io_bitmap, 0xff, prev->io_bitmap_max);
- }
+ switch_io_bitmap(tss, prev_p, next_p);
propagate_user_return_notify(prev_p, next_p);
}

diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
index 73a38c8..38eaae4 100644
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -154,7 +154,7 @@ int copy_thread(unsigned long clone_flags, unsigned long sp,
childregs->cs = __KERNEL_CS | get_kernel_rpl();
childregs->flags = X86_EFLAGS_IF | X86_EFLAGS_FIXED;
p->thread.fpu_counter = 0;
- p->thread.io_bitmap_ptr = NULL;
+ clear_thread_io_bitmap(p);
memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps));
return 0;
}
@@ -167,7 +167,7 @@ int copy_thread(unsigned long clone_flags, unsigned long sp,
task_user_gs(p) = get_user_gs(current_pt_regs());

p->thread.fpu_counter = 0;
- p->thread.io_bitmap_ptr = NULL;
+ clear_thread_io_bitmap(p);
tsk = current;

memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps));
@@ -269,14 +269,7 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
*/
load_TLS(next, cpu);

- /*
- * Restore IOPL if needed. In normal use, the flags restore
- * in the switch assembly will handle this. But if the kernel
- * is running virtualized at a non-zero CPL, the popf will
- * not restore flags, so it must be done in a separate step.
- */
- if (get_kernel_rpl() && unlikely(prev->iopl != next->iopl))
- set_iopl_mask(next->iopl);
+ switch_iopl_mask(prev, next);

/*
* If it were not for PREEMPT_ACTIVE we could guarantee that the
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 3b8f17c..7eb9adc 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -165,7 +165,7 @@ int copy_thread(unsigned long clone_flags, unsigned long sp,
p->thread.usersp = me->thread.usersp;
set_tsk_thread_flag(p, TIF_FORK);
p->thread.fpu_counter = 0;
- p->thread.io_bitmap_ptr = NULL;
+ clear_thread_io_bitmap(p);

savesegment(gs, p->thread.gsindex);
p->thread.gs = p->thread.gsindex ? 0 : me->thread.gs;
diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
index 7461f50..f071bfa 100644
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -785,7 +785,11 @@ static int ptrace_set_debugreg(struct task_struct *tsk, int n,
static int ioperm_active(struct task_struct *target,
const struct user_regset *regset)
{
+#ifdef CONFIG_X86_IOPORT
return target->thread.io_bitmap_max / regset->size;
+#else
+ return 0;
+#endif
}

static int ioperm_get(struct task_struct *target,
@@ -793,12 +797,16 @@ static int ioperm_get(struct task_struct *target,
unsigned int pos, unsigned int count,
void *kbuf, void __user *ubuf)
{
+#ifdef CONFIG_X86_IOPORT
if (!target->thread.io_bitmap_ptr)
return -ENXIO;

return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
target->thread.io_bitmap_ptr,
0, IO_BITMAP_BYTES);
+#else
+ return -ENXIO;
+#endif
}

/*
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 201d09a..0de20ba 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -912,6 +912,7 @@ static void xen_load_sp0(struct tss_struct *tss,
xen_mc_issue(PARAVIRT_LAZY_CPU);
}

+#ifdef CONFIG_X86_IOPORT
static void xen_set_iopl_mask(unsigned mask)
{
struct physdev_set_iopl set_iopl;
@@ -920,6 +921,7 @@ static void xen_set_iopl_mask(unsigned mask)
set_iopl.iopl = (mask == 0) ? 1 : (mask >> 12) & 3;
HYPERVISOR_physdev_op(PHYSDEVOP_set_iopl, &set_iopl);
}
+#endif /* CONFIG_X86_IOPORT */

static void xen_io_delay(void)
{
@@ -1279,7 +1281,9 @@ static const struct pv_cpu_ops xen_cpu_ops __initconst = {
.write_idt_entry = xen_write_idt_entry,
.load_sp0 = xen_load_sp0,

+#ifdef CONFIG_X86_IOPORT
.set_iopl_mask = xen_set_iopl_mask,
+#endif /* CONFIG_X86_IOPORT */
.io_delay = xen_io_delay,

/* Xen takes care of %gs when switching to usermode for us */
diff --git a/drivers/tty/vt/vt_ioctl.c b/drivers/tty/vt/vt_ioctl.c
index 2bd78e2..7c7d405 100644
--- a/drivers/tty/vt/vt_ioctl.c
+++ b/drivers/tty/vt/vt_ioctl.c
@@ -410,7 +410,7 @@ int vt_ioctl(struct tty_struct *tty,
*
* XXX: you should never use these, just call ioperm directly..
*/
-#ifdef CONFIG_X86
+#ifdef CONFIG_X86_IOPORT
case KDADDIO:
case KDDELIO:
/*
diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c
index 7078052..e7f4a35 100644
--- a/kernel/sys_ni.c
+++ b/kernel/sys_ni.c
@@ -209,3 +209,8 @@ cond_syscall(compat_sys_open_by_handle_at);

/* compare kernel pointers */
cond_syscall(sys_kcmp);
+
+/* userspace I/O port access */
+cond_syscall(stub_iopl);
+cond_syscall(sys_iopl);
+cond_syscall(sys_ioperm);
--
1.9.0

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