Re: [Qemu-devel] [PATCH] linux-user: emulate msgsnd(), msgrcv() and semtimedop()

[Laurent Vivier]

On 28/05/2019 21:53, Laurent Vivier wrote:
> When we have updated kernel headers to 5.2-rc1 we have introduced
> new syscall numbers that can be not supported by older kernels
> and fail with ENOSYS while the guest emulation succeeded before
> because the syscalls were emulated with ipc().
>
> This patch fixes the problem by using ipc() if the new syscall
> returns ENOSYS.
>
> Fixes: 86e636951ddc ("linux-user: fix __NR_semtimedop undeclared error")
> Signed-off-by: Laurent Vivier <address@hidden>
> ---
>   linux-user/syscall.c      | 61 +++++++++++++++++++--------------------
>   linux-user/syscall_defs.h |  1 +
>   2 files changed, 31 insertions(+), 31 deletions(-)
>
> diff --git a/linux-user/syscall.c b/linux-user/syscall.c
> index 5e29e675e9cf..bbd185bbff74 100644
> --- a/linux-user/syscall.c
> +++ b/linux-user/syscall.c
> @@ -763,50 +763,21 @@ safe_syscall2(int, nanosleep, const struct timespec *, 
> req,
>   safe_syscall4(int, clock_nanosleep, const clockid_t, clock, int, flags,
>                 const struct timespec *, req, struct timespec *, rem)
>   #endif
> -#if !defined(__NR_msgsnd) || !defined(__NR_msgrcv) || !defined(__NR_semtimedop)
> -/* This host kernel architecture uses a single ipc syscall; fake up
> - * wrappers for the sub-operations to hide this implementation detail.
> - * Annoyingly we can't include linux/ipc.h to get the constant definitions
> - * for the call parameter because some structs in there conflict with the
> - * sys/ipc.h ones. So we just define them here, and rely on them being
> - * the same for all host architectures.
> - */
> -#define Q_SEMTIMEDOP 4
> -#define Q_MSGSND 11
> -#define Q_MSGRCV 12
> -#define Q_IPCCALL(VERSION, OP) ((VERSION) << 16 | (OP))
> -
> +#ifdef __NR_ipc
>   safe_syscall6(int, ipc, int, call, long, first, long, second, long, third,
>                 void *, ptr, long, fifth)
>   #endif
>   #ifdef __NR_msgsnd
>   safe_syscall4(int, msgsnd, int, msgid, const void *, msgp, size_t, sz,
>                 int, flags)
> -#else
> -static int safe_msgsnd(int msgid, const void *msgp, size_t sz, int flags)
> -{
> -    return safe_ipc(Q_IPCCALL(0, Q_MSGSND), msgid, sz, flags, (void *)msgp, 0);
> -}
>   #endif
>   #ifdef __NR_msgrcv
>   safe_syscall5(int, msgrcv, int, msgid, void *, msgp, size_t, sz,
>                 long, msgtype, int, flags)
> -#else
> -static int safe_msgrcv(int msgid, void *msgp, size_t sz, long type, int flags)
> -{
> -    return safe_ipc(Q_IPCCALL(1, Q_MSGRCV), msgid, sz, flags, msgp, type);
> -}
>   #endif
>   #ifdef __NR_semtimedop
>   safe_syscall4(int, semtimedop, int, semid, struct sembuf *, tsops,
>                 unsigned, nsops, const struct timespec *, timeout)
> -#else
> -static int safe_semtimedop(int semid, struct sembuf *tsops, unsigned nsops,
> -                           const struct timespec *timeout)
> -{
> -    return safe_ipc(Q_IPCCALL(0, Q_SEMTIMEDOP), semid, nsops, 0, tsops,
> -                    (long)timeout);
> -}
>   #endif
>   #if defined(TARGET_NR_mq_open) && defined(__NR_mq_open)
>   safe_syscall5(int, mq_timedsend, int, mqdes, const char *, msg_ptr,
> @@ -3530,11 +3501,21 @@ static inline abi_long target_to_host_sembuf(struct 
> sembuf *host_sembuf,
>   static inline abi_long do_semop(int semid, abi_long ptr, unsigned nsops)
>   {
>       struct sembuf sops[nsops];
> +    abi_long ret;
>   
>       if (target_to_host_sembuf(sops, ptr, nsops))
>           return -TARGET_EFAULT;
>   
> -    return get_errno(safe_semtimedop(semid, sops, nsops, NULL));
> +    ret = -ENOSYS;

this and following ones must be TARGET_ENOSYS.

I send a v2.

Thanks,
Laurent