Re: [Qemu-devel] [PATCH v2] linux-user: fix preadv/pwritev offsets

[Laurent Vivier]

Le 05/04/2018 à 03:41, Max Filippov a écrit :
> preadv/pwritev accept low and high parts of file offset in two separate
> parameters. When host bitness doesn't match guest bitness these parts
> must be appropriately recombined.
> Introduce target_low_high_to_host_low_high that does this recombination
> and use it in preadv/pwritev syscalls.
> 
> This fixes glibc testsuite test misc/tst-preadvwritev64.
> 
> Signed-off-by: Max Filippov <address@hidden>
> ---
> Changes v1->v2:
> - fix host high computation in TARGET_LONG_BITS > HOST_LONG_BITS case
> 
>  linux-user/syscall.c | 27 +++++++++++++++++++++++++--
>  1 file changed, 25 insertions(+), 2 deletions(-)
> 
> diff --git a/linux-user/syscall.c b/linux-user/syscall.c
> index 5ef517613577..7e014066260a 100644
> --- a/linux-user/syscall.c
> +++ b/linux-user/syscall.c
> @@ -3386,6 +3386,23 @@ static abi_long do_getsockopt(int sockfd, int level, 
> int optname,
>      return ret;
>  }
>  
> +static void target_low_high_to_host_low_high(abi_ulong tlow,
> +                                             abi_ulong thigh,
> +                                             unsigned long *hlow,
> +                                             unsigned long *hhigh)
> +{
> +#if TARGET_LONG_BITS == HOST_LONG_BITS
> +        *hlow = tlow;
> +        *hhigh = thigh;
> +#elif TARGET_LONG_BITS < HOST_LONG_BITS
> +        *hlow = tlow | (unsigned long)thigh << TARGET_LONG_BITS;
> +        *hhigh = 0;
> +#else
> +        *hlow = (unsigned long)tlow;
> +        *hhigh = (unsigned long)(tlow >> HOST_LONG_BITS);
> +#endif
> +}
> +
>  static struct iovec *lock_iovec(int type, abi_ulong target_addr,
>                                  abi_ulong count, int copy)
>  {
> @@ -10449,7 +10466,10 @@ abi_long do_syscall(void *cpu_env, int num, abi_long 
> arg1,
>          {
>              struct iovec *vec = lock_iovec(VERIFY_WRITE, arg2, arg3, 0);
>              if (vec != NULL) {
> -                ret = get_errno(safe_preadv(arg1, vec, arg3, arg4, arg5));
> +                unsigned long low, high;
> +
> +                target_low_high_to_host_low_high(arg4, arg5, &low, &high);
> +                ret = get_errno(safe_preadv(arg1, vec, arg3, low, high));
>                  unlock_iovec(vec, arg2, arg3, 1);
>              } else {
>                  ret = -host_to_target_errno(errno);
> @@ -10462,7 +10482,10 @@ abi_long do_syscall(void *cpu_env, int num, abi_long 
> arg1,
>          {
>              struct iovec *vec = lock_iovec(VERIFY_READ, arg2, arg3, 1);
>              if (vec != NULL) {
> -                ret = get_errno(safe_pwritev(arg1, vec, arg3, arg4, arg5));
> +                unsigned long low, high;
> +
> +                target_low_high_to_host_low_high(arg4, arg5, &low, &high);
> +                ret = get_errno(safe_pwritev(arg1, vec, arg3, low, high));
>                  unlock_iovec(vec, arg2, arg3, 0);
>              } else {
>                  ret = -host_to_target_errno(errno);
> 

Did you try to use the regpairs_aligned() and target_offset64()
functions as it is done for pread64(), pwrite64(), fadvise64(),... ?

Thanks,
Laurent