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    Subject[PATCH 025/109] net: socket: add __compat_sys_recvfrom() helper; remove in-kernel call to compat syscall
    Date
    Using the net-internal helper __compat_sys_recvfrom() allows us to avoid
    the internal calls to the compat_sys_recvfrom() syscall.

    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: David S. Miller <davem@davemloft.net>
    Cc: netdev@vger.kernel.org
    Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
    ---
    net/compat.c | 23 ++++++++++++++++-------
    1 file changed, 16 insertions(+), 7 deletions(-)

    diff --git a/net/compat.c b/net/compat.c
    index 9e0d030063ad..513adc8d0e0f 100644
    --- a/net/compat.c
    +++ b/net/compat.c
    @@ -753,18 +753,25 @@ COMPAT_SYSCALL_DEFINE3(recvmsg, int, fd, struct compat_msghdr __user *, msg, uns
    flags | MSG_CMSG_COMPAT, false);
    }

    +static inline long __compat_sys_recvfrom(int fd, void __user *buf,
    + compat_size_t len, unsigned int flags,
    + struct sockaddr __user *addr,
    + int __user *addrlen)
    +{
    + return __sys_recvfrom(fd, buf, len, flags | MSG_CMSG_COMPAT, addr,
    + addrlen);
    +}
    +
    COMPAT_SYSCALL_DEFINE4(recv, int, fd, void __user *, buf, compat_size_t, len, unsigned int, flags)
    {
    - return __sys_recvfrom(fd, buf, len, flags | MSG_CMSG_COMPAT, NULL,
    - NULL);
    + return __compat_sys_recvfrom(fd, buf, len, flags, NULL, NULL);
    }

    COMPAT_SYSCALL_DEFINE6(recvfrom, int, fd, void __user *, buf, compat_size_t, len,
    unsigned int, flags, struct sockaddr __user *, addr,
    int __user *, addrlen)
    {
    - return __sys_recvfrom(fd, buf, len, flags | MSG_CMSG_COMPAT, addr,
    - addrlen);
    + return __compat_sys_recvfrom(fd, buf, len, flags, addr, addrlen);
    }

    COMPAT_SYSCALL_DEFINE5(recvmmsg, int, fd, struct compat_mmsghdr __user *, mmsg,
    @@ -845,11 +852,13 @@ COMPAT_SYSCALL_DEFINE2(socketcall, int, call, u32 __user *, args)
    compat_ptr(a[4]), a[5]);
    break;
    case SYS_RECV:
    - ret = compat_sys_recv(a0, compat_ptr(a1), a[2], a[3]);
    + ret = __compat_sys_recvfrom(a0, compat_ptr(a1), a[2], a[3],
    + NULL, NULL);
    break;
    case SYS_RECVFROM:
    - ret = compat_sys_recvfrom(a0, compat_ptr(a1), a[2], a[3],
    - compat_ptr(a[4]), compat_ptr(a[5]));
    + ret = __compat_sys_recvfrom(a0, compat_ptr(a1), a[2], a[3],
    + compat_ptr(a[4]),
    + compat_ptr(a[5]));
    break;
    case SYS_SHUTDOWN:
    ret = __sys_shutdown(a0, a1);
    --
    2.16.3
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