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    Subject[PATCH 13/45] fs: add do_compat_select() helper; remove in-kernel call to comapt syscall
    Date
    Using the fs-internal do_compat_select() helper allows us to get rid of
    the fs-internal call to the compat_sys_select() syscall.

    This patch is part of a series which tries to remove in-kernel calls to
    syscalls. On this basis, the syscall entry path can be streamlined.

    Cc: Al Viro <viro@zeniv.linux.org.uk>
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
    ---
    fs/select.c | 17 ++++++++++++-----
    1 file changed, 12 insertions(+), 5 deletions(-)

    diff --git a/fs/select.c b/fs/select.c
    index b5df01c4587d..ba879c51288f 100644
    --- a/fs/select.c
    +++ b/fs/select.c
    @@ -1265,9 +1265,9 @@ static int compat_core_sys_select(int n, compat_ulong_t __user *inp,
    return ret;
    }

    -COMPAT_SYSCALL_DEFINE5(select, int, n, compat_ulong_t __user *, inp,
    - compat_ulong_t __user *, outp, compat_ulong_t __user *, exp,
    - struct compat_timeval __user *, tvp)
    +static int do_compat_select(int n, compat_ulong_t __user *inp,
    + compat_ulong_t __user *outp, compat_ulong_t __user *exp,
    + struct compat_timeval __user *tvp)
    {
    struct timespec64 end_time, *to = NULL;
    struct compat_timeval tv;
    @@ -1290,6 +1290,13 @@ COMPAT_SYSCALL_DEFINE5(select, int, n, compat_ulong_t __user *, inp,
    return ret;
    }

    +COMPAT_SYSCALL_DEFINE5(select, int, n, compat_ulong_t __user *, inp,
    + compat_ulong_t __user *, outp, compat_ulong_t __user *, exp,
    + struct compat_timeval __user *, tvp)
    +{
    + return do_compat_select(n, inp, outp, exp, tvp);
    +}
    +
    struct compat_sel_arg_struct {
    compat_ulong_t n;
    compat_uptr_t inp;
    @@ -1304,8 +1311,8 @@ COMPAT_SYSCALL_DEFINE1(old_select, struct compat_sel_arg_struct __user *, arg)

    if (copy_from_user(&a, arg, sizeof(a)))
    return -EFAULT;
    - return compat_sys_select(a.n, compat_ptr(a.inp), compat_ptr(a.outp),
    - compat_ptr(a.exp), compat_ptr(a.tvp));
    + return do_compat_select(a.n, compat_ptr(a.inp), compat_ptr(a.outp),
    + compat_ptr(a.exp), compat_ptr(a.tvp));
    }

    static long do_compat_pselect(int n, compat_ulong_t __user *inp,
    --
    2.16.2
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