4 files changed, 27 insertions, 6 deletions

diff --git a/arch/i386/kernel/ioport.c b/arch/i386/kernel/ioport.c
index 8b25160393c1..f2b37654777f 100644
--- a/arch/i386/kernel/ioport.c
+++ b/arch/i386/kernel/ioport.c
@@ -132,6 +132,7 @@ 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 = &current->thread;
 
         if (level > 3)
                 return -EINVAL;
@@ -140,8 +141,8 @@ asmlinkage long sys_iopl(unsigned long unused)
                 if (!capable(CAP_SYS_RAWIO))
                         return -EPERM;
         }
-        regs->eflags = (regs->eflags &~ 0x3000UL) | (level << 12);
-        /* Make sure we return the long way (not sysenter) */
-        set_thread_flag(TIF_IRET);
+        t->iopl = level << 12;
+        regs->eflags = (regs->eflags & ~X86_EFLAGS_IOPL) | t->iopl;
+        set_iopl_mask(t->iopl);
         return 0;
 }
diff --git a/arch/i386/kernel/process.c b/arch/i386/kernel/process.c
index 660997800393..b45cbf93d439 100644
--- a/arch/i386/kernel/process.c
+++ b/arch/i386/kernel/process.c
@@ -712,6 +712,12 @@ struct task_struct fastcall * __switch_to(struct task_struct *prev_p, struct tas
                 loadsegment(gs, next->gs);
 
         /*
+         * Restore IOPL if needed.
+         */
+        if (unlikely(prev->iopl != next->iopl))
+                set_iopl_mask(next->iopl);
+
+        /*
          * Now maybe reload the debug registers
          */
         if (unlikely(next->debugreg[7])) {
diff --git a/include/asm-i386/processor.h b/include/asm-i386/processor.h
index 992224bff549..37bef8ed7bed 100644
--- a/include/asm-i386/processor.h
+++ b/include/asm-i386/processor.h
@@ -455,6 +455,7 @@ struct thread_struct {
         unsigned int            saved_fs, saved_gs;
 /* IO permissions */
         unsigned long   *io_bitmap_ptr;
+        unsigned long   iopl;
 /* max allowed port in the bitmap, in bytes: */
         unsigned long   io_bitmap_max;
 };
@@ -511,6 +512,21 @@ static inline void load_esp0(struct tss_struct *tss, struct thread_struct *threa
                         : /* no output */                       \
                         :"r" (value))
 
+/*
+ * Set IOPL bits in EFLAGS from given mask
+ */
+static inline void set_iopl_mask(unsigned mask)
+{
+        unsigned int reg;
+        __asm__ __volatile__ ("pushfl;"
+                              "popl %0;"
+                              "andl %1, %0;"
+                              "orl %2, %0;"
+                              "pushl %0;"
+                              "popfl"
+                                : "=&r" (reg)
+                                : "i" (~X86_EFLAGS_IOPL), "r" (mask));
+}
 
 /* Forward declaration, a strange C thing */
 struct task_struct;
diff --git a/include/asm-i386/system.h b/include/asm-i386/system.h
index 37fd2f8c7196..acd5c26b69ba 100644
--- a/include/asm-i386/system.h
+++ b/include/asm-i386/system.h
@@ -14,8 +14,7 @@ extern struct task_struct * FASTCALL(__switch_to(struct task_struct *prev, struc
 
 #define switch_to(prev,next,last) do {                                  \
         unsigned long esi,edi;                                          \
-        asm volatile("pushfl\n\t"                                       \
-                     "pushl %%ebp\n\t"                                  \
+        asm volatile("pushl %%ebp\n\t"                                  \
                      "movl %%esp,%0\n\t"        /* save ESP */          \
                      "movl %5,%%esp\n\t"        /* restore ESP */       \
                      "movl $1f,%1\n\t"          /* save EIP */          \
@@ -23,7 +22,6 @@ extern struct task_struct * FASTCALL(__switch_to(struct task_struct *prev, struc
                      "jmp __switch_to\n"                                \
                      "1:\t"                                             \
                      "popl %%ebp\n\t"                                   \
-                     "popfl"                                            \
                      :"=m" (prev->thread.esp),"=m" (prev->thread.eip),  \
                       "=a" (last),"=S" (esi),"=D" (edi)                 \
                      :"m" (next->thread.esp),"m" (next->thread.eip),    \