Re: [PATCH v2 2/2] linux-user: Add support for utimensat_time64() and semtimedop_time64()

[Laurent Vivier <laurent@vivier.eu>]

Le 26/08/2020 à 15:58, Laurent Vivier a écrit :
> Le 25/08/2020 à 16:23, Laurent Vivier a écrit :
>> Le 25/08/2020 à 09:18, Laurent Vivier a écrit :
>>> Le 25/08/2020 à 00:30, Filip Bozuta a écrit :
>>>> This patch introduces functionality for following time64 syscalls:
>>>>
>>>> *utimensat_time64()
>>>>
>>>>     int utimensat(int dirfd, const char *pathname,
>>>>                   const struct timespec times[2], int flags);
>>>>     -- change file timestamps with nanosecond precision --
>>>>     man page: https://man7.org/linux/man-pages/man2/utimensat.2.html
>>>>
>>>> *semtimedop_time64()
>>>>
>>>>     int semtimedop(int semid, struct sembuf *sops, size_t nsops,
>>>>                    const struct timespec *timeout);
>>>>     -- System V semaphore operations --
>>>>     man page: https://www.man7.org/linux/man-pages/man2/semtimedop.2.html
>>>>
>>>> Implementation notes:
>>>>
>>>>    Syscall 'utimensat_time64()' is implemented in similar way as its
>>>>    regular variants only difference being that time64 converting function
>>>>    is used to convert values of 'struct timespec' between host and target
>>>>    ('target_to_host_timespec64()').
>>>>
>>>>    For syscall 'semtimedop_time64()' and additional argument is added
>>>>    in function 'do_semtimedop()' through which the aproppriate 'struct timespec'
>>>>    converting function is called (false for regular target_to_host_timespec()
>>>>    and true for target_to_host_timespec64()). For 'do_ipc()' a
>>>>    check was added as that additional argument: 'TARGET_ABI_BITS == 64'.
>>>>
>>>> Signed-off-by: Filip Bozuta <Filip.Bozuta@syrmia.com>
>>>> Reviewed-by: Laurent Vivier <laurent@vivier.eu>
>>>> ---
>>>>  linux-user/syscall.c | 60 ++++++++++++++++++++++++++++++++++++--------
>>>>  1 file changed, 50 insertions(+), 10 deletions(-)
>>>>
>>>> diff --git a/linux-user/syscall.c b/linux-user/syscall.c
>>>> index fc6a6e32e4..4d460af744 100644
>>>> --- a/linux-user/syscall.c
>>>> +++ b/linux-user/syscall.c
>>>> @@ -1253,7 +1253,8 @@ static inline abi_long target_to_host_timespec(struct timespec *host_ts,
>>>>  #endif
>>>>  
>>>>  #if defined(TARGET_NR_clock_settime64) || defined(TARGET_NR_futex_time64) || \
>>>> -    defined(TARGET_NR_pselect6_time64) || defined(TARGET_NR_ppoll_time64)
>>>> +    defined(TARGET_NR_pselect6_time64) || defined(TARGET_NR_ppoll_time64) || \
>>>> +    defined(TARGET_NR_utimensat_time64) || defined(TARGET_NR_semtimedop_time64)
>>>>  static inline abi_long target_to_host_timespec64(struct timespec *host_ts,
>>>>                                                   abi_ulong target_addr)
>>>>  {
>>>> @@ -4117,7 +4118,7 @@ static inline abi_long target_to_host_sembuf(struct sembuf *host_sembuf,
>>>>  }
>>>>  
>>>>  #if defined(TARGET_NR_ipc) || defined(TARGET_NR_semop) || \
>>>> -    defined(TARGET_NR_semtimedop)
>>>> +    defined(TARGET_NR_semtimedop) || defined(TARGET_NR_semtimedop_time64)
>>>>  
>>>>  /*
>>>>   * This macro is required to handle the s390 variants, which passes the
>>>> @@ -4134,7 +4135,7 @@ static inline abi_long target_to_host_sembuf(struct sembuf *host_sembuf,
>>>>  static inline abi_long do_semtimedop(int semid,
>>>>                                       abi_long ptr,
>>>>                                       unsigned nsops,
>>>> -                                     abi_long timeout)
>>>> +                                     abi_long timeout, bool time64)
>>>>  {
>>>>      struct sembuf sops[nsops];
>>>>      struct timespec ts, *pts = NULL;
>>>> @@ -4142,8 +4143,14 @@ static inline abi_long do_semtimedop(int semid,
>>>>  
>>>>      if (timeout) {
>>>>          pts = &ts;
>>>> -        if (target_to_host_timespec(pts, timeout)) {
>>>> -            return -TARGET_EFAULT;
>>>> +        if (time64) {
>>>> +            if (target_to_host_timespec64(pts, timeout)) {
>>>> +                return -TARGET_EFAULT;
>>>> +            }
>>>> +        } else {
>>>> +            if (target_to_host_timespec(pts, timeout)) {
>>>> +                return -TARGET_EFAULT;
>>>> +            }
>>>>          }
>>>>      }
>>>>  
>>>> @@ -4657,7 +4664,7 @@ static abi_long do_ipc(CPUArchState *cpu_env,
>>>>  
>>>>      switch (call) {
>>>>      case IPCOP_semop:
>>>> -        ret = do_semtimedop(first, ptr, second, 0);
>>>> +        ret = do_semtimedop(first, ptr, second, 0, false);
>>>>          break;
>>>>      case IPCOP_semtimedop:
>>>>      /*
>>>> @@ -4667,9 +4674,9 @@ static abi_long do_ipc(CPUArchState *cpu_env,
>>>>       * to a struct timespec where the generic variant uses fifth parameter.
>>>>       */
>>>>  #if defined(TARGET_S390X)
>>>> -        ret = do_semtimedop(first, ptr, second, third);
>>>> +        ret = do_semtimedop(first, ptr, second, third, TARGET_ABI_BITS == 64);
>>>>  #else
>>>> -        ret = do_semtimedop(first, ptr, second, fifth);
>>>> +        ret = do_semtimedop(first, ptr, second, fifth, TARGET_ABI_BITS == 64);
>>>>  #endif
>>>>          break;
>>>>  
>>>> @@ -9887,11 +9894,15 @@ static abi_long do_syscall1(void *cpu_env, int num, abi_long arg1,
>>>>  #endif
>>>>  #ifdef TARGET_NR_semop
>>>>      case TARGET_NR_semop:
>>>> -        return do_semtimedop(arg1, arg2, arg3, 0);
>>>> +        return do_semtimedop(arg1, arg2, arg3, 0, false);
>>>>  #endif
>>>>  #ifdef TARGET_NR_semtimedop
>>>>      case TARGET_NR_semtimedop:
>>>> -        return do_semtimedop(arg1, arg2, arg3, arg4);
>>>> +        return do_semtimedop(arg1, arg2, arg3, arg4, false);
>>>> +#endif
>>>> +#ifdef TARGET_NR_semtimedop_time64
>>>> +    case TARGET_NR_semtimedop_time64:
>>>> +        return do_semtimedop(arg1, arg2, arg3, arg4, true);
>>>>  #endif
>>>>  #ifdef TARGET_NR_semctl
>>>>      case TARGET_NR_semctl:
>>>> @@ -11938,6 +11949,35 @@ static abi_long do_syscall1(void *cpu_env, int num, abi_long arg1,
>>>>          }
>>>>          return ret;
>>>>  #endif
>>>> +#ifdef TARGET_NR_utimensat_time64
>>>> +    case TARGET_NR_utimensat_time64:
>>>> +        {
>>>> +            struct timespec *tsp, ts[2];
>>>> +            if (!arg3) {
>>>> +                tsp = NULL;
>>>> +            } else {
>>>> +                if (target_to_host_timespec64(ts, arg3)) {
>>>> +                    return -TARGET_EFAULT;
>>>> +                }
>>>> +                if (target_to_host_timespec64(ts + 1, arg3 +
>>>> +                                     sizeof(struct target__kernel_timespec))) {
>>>> +                    return -TARGET_EFAULT;
>>>> +                }
>>>> +                tsp = ts;
>>>> +            }
>>>> +            if (!arg2)
>>>> +                ret = get_errno(sys_utimensat(arg1, NULL, tsp, arg4));
>>>> +            else {
>>>> +                p = lock_user_string(arg2);
>>>> +                if (!p) {
>>>> +                    return -TARGET_EFAULT;
>>>> +                }
>>>> +                ret = get_errno(sys_utimensat(arg1, path(p), tsp, arg4));
>>>> +                unlock_user(p, arg2, 0);
>>>> +            }
>>>> +        }
>>>> +        return ret;
>>>> +#endif
>>>>  #ifdef TARGET_NR_futex
>>>>      case TARGET_NR_futex:
>>>>          return do_futex(arg1, arg2, arg3, arg4, arg5, arg6);
>>>>
>>>
>>> Applied to my linux-user-for-5.2 branch.
>>
>> I have removed it from my queue because the "TARGET_NR_utimensat_time64"
>> part breaks something (at least with sh4/sid on x86_64):
>>
>> $ touch a
>> $ cp -p a b
>> /usr/bin/cp: preserving times for 'b': Invalid argument
> 
> In fact, on sh4, he timespec64 conversion is broken for all syscalls.
> tv_sec is ok but tv_nsec is totally corrupted (as it would be only a
> 32bit value).

In kernel, in get_timespec64(), we have:

            /* In 32-bit mode, this drops the padding */
            ts->tv_nsec = kts.tv_nsec;

and ts is "struct timespec64" (kts is __kernel_timespec):

    struct timespec64 {
            time64_t        tv_sec;                 /* seconds */
            long            tv_nsec;                /* nanoseconds */
    };

So I think we need something like:

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index c82b73e03234..5f53d5d65eb6 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -1253,6 +1253,8 @@ static inline abi_long
target_to_host_timespec64(struct timespec *host_ts,
     }
     __get_user(host_ts->tv_sec, &target_ts->tv_sec);
     __get_user(host_ts->tv_nsec, &target_ts->tv_nsec);
+    /* in 32bit mode this drops the padding */
+    host_ts->tv_nsec = (abi_long)host_ts->tv_nsec;
     unlock_user_struct(target_ts, target_addr, 0);
     return 0;
 }

Thanks,
Laurent