Re: [Qemu-devel] [PATCH] linux-user: Implement sendmmsg syscall

[Laurent Vivier]

> Le 5 septembre 2013 à 15:37, Alexander Graf <address@hidden> a écrit :
>
>
> Glibc when built for newer kernels assumes that the sendmmsg syscall is available.
> Without it, dns resolution simply fails to work.
>
> Wrap the syscall with existing infrastructure so that we don't have a host dependency
> on sendmmsg.

 

Why don't you write a "do_sendrecvmmsg()" in the same way it is done for "do_sendrecvmsg()" to be able to manage also the "recvmmsg()" syscall ?

 

Regards,

Laurent

> Signed-off-by: Alexander Graf <address@hidden>
> ---
> linux-user/syscall.c | 29 +++++++++++++++++++++++++++++
> linux-user/syscall_defs.h | 4 ++++
> 2 files changed, 33 insertions(+)
>
> diff --git a/linux-user/syscall.c b/linux-user/syscall.c
> index 0272990..59cfdf4 100644
> --- a/linux-user/syscall.c
> +++ b/linux-user/syscall.c
> @@ -1863,6 +1863,30 @@ out2:
> return ret;
> }
>
> +#ifdef TARGET_NR_sendmmsg
> +static abi_long do_sendmmsg(int fd, abi_ulong target_msgvec,
> + unsigned int vlen, unsigned int flags)
> +{
> + struct target_mmsghdr *mmsgp;
> + abi_ulong arg2 = target_msgvec;
> + int i;
> +
> + if (!(mmsgp = lock_user(VERIFY_WRITE, target_msgvec,
> + sizeof(*mmsgp) * vlen, 1))) {
> + return -TARGET_EFAULT;
> + }
> +
> + for (i = 0; i < vlen; i++) {
> + mmsgp[i].msg_len = tswap32(do_sendrecvmsg(fd, arg2, flags, 1));
> + arg2 += sizeof(struct target_mmsghdr);
> + }
> +
> + unlock_user(mmsgp, target_msgvec, 0);
> + /* XXX need to handle nonblocking case too */
> + return vlen;
> +}
> +#endif
> +
> /* If we don't have a system accept4() then just call accept.
> * The callsites to do_accept4() will ensure that they don't
> * pass a non-zero flags argument in this config.
> @@ -6973,6 +6997,11 @@ abi_long do_syscall(void *cpu_env, int num, abi_ulong arg1,
> ret = do_sendrecvmsg(arg1, arg2, arg3, 1);
> break;
> #endif
> +#ifdef TARGET_NR_sendmmsg
> + case TARGET_NR_sendmmsg:
> + ret = do_sendmmsg(arg1, arg2, arg3, arg4);
> + break;
> +#endif
> #ifdef TARGET_NR_sendto
> case TARGET_NR_sendto:
> ret = do_sendto(arg1, arg2, arg3, arg4, arg5, arg6);
> diff --git a/linux-user/syscall_defs.h b/linux-user/syscall_defs.h
> index e51ef31..37645de 100644
> --- a/linux-user/syscall_defs.h
> +++ b/linux-user/syscall_defs.h
> @@ -222,6 +222,10 @@ __target_cmsg_nxthdr (struct target_msghdr *__mhdr, struct target_cmsghdr *__cms
> return __cmsg;
> }
>
> +struct target_mmsghdr {
> + struct target_msghdr msg_hdr; /* Message header */
> + unsigned int msg_len; /* Number of bytes transmitted */
> +};
>
> struct target_rusage {
> struct target_timeval ru_utime; /* user time used */
> --
> 1.8.1.4
>
>