Re: [Qemu-devel] [PATCH v5 4/8] linux-user: Add support for ustat() syscall

[Laurent Vivier]

Le 14/09/2016 à 22:19, Aleksandar Markovic a écrit :
> From: Aleksandar Markovic <address@hidden>
> 
> This patch implements Qemu user mode ustat() syscall support.
> 
> Syscall ustat() returns information about a mounted filesystem.
> 
> The implementation is similar to the implementations of statfs(),
> fstatfs() and other related syscalls. It is based on invocation of
> host's ustat(), and its key part is in the correspondent case segment
> of the main switch statement of the function do_syscall(), in file
> linux-user/syscalls.c. All necessary conversions of data structures
> from target to host and from host to target are covered. Sufficient
> support for "-strace" option for this syscall is already present,
> and this patch does not change it.
> 
> This patch also fixes failures of LTP tests ustat01, and ustat02, if
> executed on Qemu-emulated systems.
> 
> Signed-off-by: Aleksandar Markovic <address@hidden>
> ---
>  linux-user/syscall.c | 25 ++++++++++++++++++++++++-
>  1 file changed, 24 insertions(+), 1 deletion(-)
> 
> diff --git a/linux-user/syscall.c b/linux-user/syscall.c
> index 3436ee6..7f8ae41 100644
> --- a/linux-user/syscall.c
> +++ b/linux-user/syscall.c
> @@ -48,6 +48,7 @@ int __clone2(int (*fn)(void *), void *child_stack_base,
>  #include <sys/shm.h>
>  #include <sys/sem.h>
>  #include <sys/statfs.h>
> +#include <ustat.h>
>  #include <utime.h>
>  #include <sys/sysinfo.h>
>  #include <sys/signalfd.h>
> @@ -8098,7 +8099,29 @@ abi_long do_syscall(void *cpu_env, int num, abi_long 
> arg1,
>          break;
>  #ifdef TARGET_NR_ustat
>      case TARGET_NR_ustat:
> -        goto unimplemented;
> +    {
> +        struct ustat ust;
> +        int cnt;
> +        ret = get_errno(ustat(arg1, &ust));
> +
> +        if (!is_error(ret)) {
> +            struct ustat *target_ust;

You must define your own "struct target_ustat" as __kernel_daddr_t and
__kernel_ino_t are long (or int).

> +
> +            if (!lock_user_struct(VERIFY_WRITE, target_ust, arg2, 0)) {
> +                goto efault;
> +            }
> +
> +            __put_user(ust.f_tfree, &target_ust->f_tfree);
> +            __put_user(ust.f_tinode, &target_ust->f_tinode);
> +
> +            for (cnt = 0; cnt < 6; cnt++) {
> +                __put_user(ust.f_fname[cnt], &target_ust->f_fname[cnt]);
> +                __put_user(ust.f_fpack[cnt], &target_ust->f_fpack[cnt]);
> +            }

As the structure is locked and they are "char", you can do memcpy().

> +            unlock_user_struct(target_ust, arg2, 1);
> +        }
> +        break;
> +      }
>  #endif
>  #ifdef TARGET_NR_dup2
>      case TARGET_NR_dup2:
> 

Laurent