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    Subject[PATCH 032/109] ipc: add semctl syscall/compat_syscall wrappers
    Date
    Provide ksys_semctl() and compat_ksys_semctl() wrappers to avoid in-kernel
    calls to these syscalls. The ksys_ prefix denotes that these functions are
    meant as a drop-in replacement for the syscalls. In particular, they use
    the same calling convention as sys_semctl() and compat_sys_semctl().

    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: Al Viro <viro@zeniv.linux.org.uk>
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
    ---
    ipc/sem.c | 14 ++++++++++++--
    ipc/syscall.c | 4 ++--
    ipc/util.h | 2 ++
    3 files changed, 16 insertions(+), 4 deletions(-)

    diff --git a/ipc/sem.c b/ipc/sem.c
    index 2e5f7ec7a7db..1cf56279a84c 100644
    --- a/ipc/sem.c
    +++ b/ipc/sem.c
    @@ -1581,7 +1581,7 @@ static int semctl_down(struct ipc_namespace *ns, int semid,
    return err;
    }

    -SYSCALL_DEFINE4(semctl, int, semid, int, semnum, int, cmd, unsigned long, arg)
    +long ksys_semctl(int semid, int semnum, int cmd, unsigned long arg)
    {
    int version;
    struct ipc_namespace *ns;
    @@ -1635,6 +1635,11 @@ SYSCALL_DEFINE4(semctl, int, semid, int, semnum, int, cmd, unsigned long, arg)
    }
    }

    +SYSCALL_DEFINE4(semctl, int, semid, int, semnum, int, cmd, unsigned long, arg)
    +{
    + return ksys_semctl(semid, semnum, cmd, arg);
    +}
    +
    #ifdef CONFIG_COMPAT

    struct compat_semid_ds {
    @@ -1683,7 +1688,7 @@ static int copy_compat_semid_to_user(void __user *buf, struct semid64_ds *in,
    }
    }

    -COMPAT_SYSCALL_DEFINE4(semctl, int, semid, int, semnum, int, cmd, int, arg)
    +long compat_ksys_semctl(int semid, int semnum, int cmd, int arg)
    {
    void __user *p = compat_ptr(arg);
    struct ipc_namespace *ns;
    @@ -1727,6 +1732,11 @@ COMPAT_SYSCALL_DEFINE4(semctl, int, semid, int, semnum, int, cmd, int, arg)
    return -EINVAL;
    }
    }
    +
    +COMPAT_SYSCALL_DEFINE4(semctl, int, semid, int, semnum, int, cmd, int, arg)
    +{
    + return compat_ksys_semctl(semid, semnum, cmd, arg);
    +}
    #endif

    /* If the task doesn't already have a undo_list, then allocate one
    diff --git a/ipc/syscall.c b/ipc/syscall.c
    index 21fcdf0b4836..a536cca37661 100644
    --- a/ipc/syscall.c
    +++ b/ipc/syscall.c
    @@ -42,7 +42,7 @@ SYSCALL_DEFINE6(ipc, unsigned int, call, int, first, unsigned long, second,
    return -EINVAL;
    if (get_user(arg, (unsigned long __user *) ptr))
    return -EFAULT;
    - return sys_semctl(first, second, third, arg);
    + return ksys_semctl(first, second, third, arg);
    }

    case MSGSND:
    @@ -138,7 +138,7 @@ COMPAT_SYSCALL_DEFINE6(ipc, u32, call, int, first, int, second,
    return -EINVAL;
    if (get_user(pad, (u32 __user *) compat_ptr(ptr)))
    return -EFAULT;
    - return compat_sys_semctl(first, second, third, pad);
    + return compat_ksys_semctl(first, second, third, pad);

    case MSGSND:
    return compat_sys_msgsnd(first, ptr, second, third);
    diff --git a/ipc/util.h b/ipc/util.h
    index 0f07056e5a73..1f1109b83437 100644
    --- a/ipc/util.h
    +++ b/ipc/util.h
    @@ -241,12 +241,14 @@ long ksys_semtimedop(int semid, struct sembuf __user *tsops,
    unsigned int nsops,
    const struct timespec __user *timeout);
    long ksys_semget(key_t key, int nsems, int semflg);
    +long ksys_semctl(int semid, int semnum, int cmd, unsigned long arg);

    /* for CONFIG_ARCH_WANT_OLD_COMPAT_IPC */
    #ifdef CONFIG_COMPAT
    long compat_ksys_semtimedop(int semid, struct sembuf __user *tsems,
    unsigned int nsops,
    const struct compat_timespec __user *timeout);
    +long compat_ksys_semctl(int semid, int semnum, int cmd, int arg);
    #endif /* CONFIG_COMPAT */

    #endif
    --
    2.16.3
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