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    Subject[PATCH 099/109] x86/ioport: add ksys_ioperm() helper; remove in-kernel calls to sys_ioperm()
    Date
    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>
    ---
    arch/x86/include/asm/syscalls.h | 1 +
    arch/x86/kernel/ioport.c | 7 ++++++-
    drivers/tty/vt/vt_ioctl.c | 6 +++---
    3 files changed, 10 insertions(+), 4 deletions(-)

    diff --git a/arch/x86/include/asm/syscalls.h b/arch/x86/include/asm/syscalls.h
    index bad25bb80679..1c0bebbd039e 100644
    --- a/arch/x86/include/asm/syscalls.h
    +++ b/arch/x86/include/asm/syscalls.h
    @@ -17,6 +17,7 @@

    /* Common in X86_32 and X86_64 */
    /* kernel/ioport.c */
    +long ksys_ioperm(unsigned long from, unsigned long num, int turn_on);
    asmlinkage long sys_ioperm(unsigned long, unsigned long, int);
    asmlinkage long sys_iopl(unsigned int);

    diff --git a/arch/x86/kernel/ioport.c b/arch/x86/kernel/ioport.c
    index 38deafebb21b..0fe1c8782208 100644
    --- a/arch/x86/kernel/ioport.c
    +++ b/arch/x86/kernel/ioport.c
    @@ -23,7 +23,7 @@
    /*
    * this changes the io permissions bitmap in the current task.
    */
    -SYSCALL_DEFINE3(ioperm, unsigned long, from, unsigned long, num, int, turn_on)
    +long ksys_ioperm(unsigned long from, unsigned long num, int turn_on)
    {
    struct thread_struct *t = &current->thread;
    struct tss_struct *tss;
    @@ -96,6 +96,11 @@ SYSCALL_DEFINE3(ioperm, unsigned long, from, unsigned long, num, int, turn_on)
    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
    diff --git a/drivers/tty/vt/vt_ioctl.c b/drivers/tty/vt/vt_ioctl.c
    index d61be307256a..a78ad10a119b 100644
    --- a/drivers/tty/vt/vt_ioctl.c
    +++ b/drivers/tty/vt/vt_ioctl.c
    @@ -57,7 +57,7 @@ extern struct tty_driver *console_driver;
    */

    #ifdef CONFIG_X86
    -#include <linux/syscalls.h>
    +#include <asm/syscalls.h>
    #endif

    static void complete_change_console(struct vc_data *vc);
    @@ -420,12 +420,12 @@ int vt_ioctl(struct tty_struct *tty,
    ret = -EINVAL;
    break;
    }
    - ret = sys_ioperm(arg, 1, (cmd == KDADDIO)) ? -ENXIO : 0;
    + ret = ksys_ioperm(arg, 1, (cmd == KDADDIO)) ? -ENXIO : 0;
    break;

    case KDENABIO:
    case KDDISABIO:
    - ret = sys_ioperm(GPFIRST, GPNUM,
    + ret = ksys_ioperm(GPFIRST, GPNUM,
    (cmd == KDENABIO)) ? -ENXIO : 0;
    break;
    #endif
    --
    2.16.3
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