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    SubjectRe: [GIT PULL] x86: unify sys_iopl
    From
    The correct fix is to move set_iopl_mask into do_iopl.  sys_iopl
    should only be a wrapper around do_iopl to manage the different
    calling convention used by 32-bit and 64-bit.

    On Fri, Sep 25, 2009 at 6:05 PM, Jeremy Fitzhardinge <jeremy@goop.org> wrote:
    > Hi Ingo,
    >
    > The x86-64 implementation of iopl was buggy because it never ended up calling
    > set_iopl_mask().  This had no effect on native sys_iopl (because set_iopl_mask
    > is normally no-op on 64-bit), but it ended up never calling the pvop, which caused
    > iopl to have no effect on 64-bit Xen guests.
    >
    > The two functions are needlessly different anyway.  This patch just unifies them
    > into a single function which is mostly derived from the 32-bit version.
    >
    > Thanks,
    >        J
    >
    > The following changes since commit c44c9ec0f38b939b3200436e3aa95c1aa83c41c7:
    >  Jeremy Fitzhardinge (1):
    >        x86: split NX setup into separate file to limit unstack-protected code
    >
    > are available in the git repository at:
    >
    >  git://git.kernel.org/pub/scm/linux/kernel/git/jeremy/xen.git bugfix
    >
    > Jeremy Fitzhardinge (1):
    >      x86: unify sys_iopl
    >
    >  arch/x86/include/asm/syscalls.h |    8 +++-----
    >  arch/x86/kernel/ioport.c        |   11 ++---------
    >  2 files changed, 5 insertions(+), 14 deletions(-)
    >
    > From 8dbb1d168eb8be6bf43d123fdfb3ba3b03762e62 Mon Sep 17 00:00:00 2001
    > From: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
    > Date: Wed, 23 Sep 2009 16:35:24 -0700
    > Subject: [PATCH] x86: unify sys_iopl
    >
    > The 32 and 64-bit versions of sys_iopl were needlessly different:
    >  - The 32-bit version ignored its function argument and directly
    >   fetched the parameter from struct regs, presumably code dating
    >   from the neolithic era.
    >  - The 64-bit version never called set_iopl_mask().  Usually this
    >   is a no-op for 64-bit, but it is also a pvop, which meant that
    >   that iopl never worked for 64-bit guests under Xen.
    >  - Both versions use the archaic style of getting pt_regs passed
    >   to them.  We can get the current pt_regs with task_pt_regs, which
    >   avoids worrying about the fine details of stack layout.
    >
    > We can use the body of the 32-bit function with a few small
    > adjustments to the function definition.
    >
    > Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
    >
    > diff --git a/arch/x86/include/asm/syscalls.h b/arch/x86/include/asm/syscalls.h
    > index 372b76e..5336ce2 100644
    > --- a/arch/x86/include/asm/syscalls.h
    > +++ b/arch/x86/include/asm/syscalls.h
    > @@ -33,11 +33,11 @@ long sys_rt_sigreturn(struct pt_regs *);
    >  asmlinkage int sys_set_thread_area(struct user_desc __user *);
    >  asmlinkage int sys_get_thread_area(struct user_desc __user *);
    >
    > -/* X86_32 only */
    > -#ifdef CONFIG_X86_32
    >  /* kernel/ioport.c */
    > -long sys_iopl(struct pt_regs *);
    > +asmlinkage long sys_iopl(unsigned int);
    >
    > +/* X86_32 only */
    > +#ifdef CONFIG_X86_32
    >  /* kernel/process_32.c */
    >  int sys_clone(struct pt_regs *);
    >  int sys_execve(struct pt_regs *);
    > @@ -70,8 +70,6 @@ int sys_vm86(struct pt_regs *);
    >  #else /* CONFIG_X86_32 */
    >
    >  /* X86_64 only */
    > -/* kernel/ioport.c */
    > -asmlinkage long sys_iopl(unsigned int, struct pt_regs *);
    >
    >  /* kernel/process_64.c */
    >  asmlinkage long sys_clone(unsigned long, unsigned long,
    > diff --git a/arch/x86/kernel/ioport.c b/arch/x86/kernel/ioport.c
    > index 99c4d30..bad4f22 100644
    > --- a/arch/x86/kernel/ioport.c
    > +++ b/arch/x86/kernel/ioport.c
    > @@ -119,11 +119,10 @@ static int do_iopl(unsigned int level, struct pt_regs *regs)
    >        return 0;
    >  }
    >
    > -#ifdef CONFIG_X86_32
    > -long sys_iopl(struct pt_regs *regs)
    > +asmlinkage long sys_iopl(unsigned int level)
    >  {
    > -       unsigned int level = regs->bx;
    >        struct thread_struct *t = &current->thread;
    > +       struct pt_regs *regs = task_pt_regs(current);
    >        int rc;
    >
    >        rc = do_iopl(level, regs);
    > @@ -135,9 +134,3 @@ long sys_iopl(struct pt_regs *regs)
    >  out:
    >        return rc;
    >  }
    > -#else
    > -asmlinkage long sys_iopl(unsigned int level, struct pt_regs *regs)
    > -{
    > -       return do_iopl(level, regs);
    > -}
    > -#endif
    >
    >
    > --
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