Re: [Qemu-devel] [PATCH] linux-user, fix getgroups/getgroups32 when both args are zero.

[Kirill A. Shutemov]

On [Sat, 23.02.2008 09:25], Kirill A. Shutemov wrote:
> On [Sat, 23.02.2008 12:00], Takashi Yoshii wrote:
> > getgroups() and getgroups32() returns NGROUPS_MAX when both its two args are
> > zero. But because we pass a ptr to allocated space as 2nd arg, this function
> > are interfered. The patch attached fixed it.
> > /yoshii
> > ---
> >     linux-user/syscall.c: fix getgroups{,32} when both args are zero.
> > 
> 
> My version of patch to fix same problem:
> 
>     getgroups: return total number of supplementary group IDs for the
>     process if size == 0
> 
> diff --git a/linux-user/syscall.c b/linux-user/syscall.c
> index ad97871..96a11a9 100644
> --- a/linux-user/syscall.c
> +++ b/linux-user/syscall.c
> @@ -5029,6 +5029,8 @@ abi_long do_syscall(void *cpu_env, int num, abi_long 
> arg1,
>  
>              grouplist = alloca(gidsetsize * sizeof(gid_t));
>              ret = get_errno(getgroups(gidsetsize, grouplist));
> +            if (gidsetsize == 0)
> +                break;
>              if (!is_error(ret)) {
>                  target_grouplist = lock_user(VERIFY_WRITE, arg2, gidsetsize 
> * 2, 0);
>                  if (!target_grouplist)
> @@ -5179,6 +5181,8 @@ abi_long do_syscall(void *cpu_env, int num, abi_long 
> arg1,
>  
>              grouplist = alloca(gidsetsize * sizeof(gid_t));
>              ret = get_errno(getgroups(gidsetsize, grouplist));
> +            if (gidsetsize == 0)
> +                break;
>              if (!is_error(ret)) {
>                  target_grouplist = lock_user(VERIFY_WRITE, arg2, gidsetsize 
> * 4, 0);
>                  if (!target_grouplist) {
> 
> Another patch for getgroups:
> 
>     Trivial optimization of getgroups syscall implementation:
>     swap only returned groups, not all group in list.
> 
> diff --git a/linux-user/syscall.c b/linux-user/syscall.c
> index 6f2872f..ad97871 100644
> --- a/linux-user/syscall.c
> +++ b/linux-user/syscall.c
> @@ -5033,7 +5033,7 @@ abi_long do_syscall(void *cpu_env, int num, abi_long 
> arg1,
>                  target_grouplist = lock_user(VERIFY_WRITE, arg2, gidsetsize 
> * 2, 0);
>                  if (!target_grouplist)
>                      goto efault;
> -                for(i = 0;i < gidsetsize; i++)
> +                for(i = 0;i < ret; i++)
>                      target_grouplist[i] = tswap16(grouplist[i]);
>                  unlock_user(target_grouplist, arg2, gidsetsize * 2);
>              }
> @@ -5185,7 +5185,7 @@ abi_long do_syscall(void *cpu_env, int num, abi_long 
> arg1,
>                      ret = -TARGET_EFAULT;
>                      goto fail;
>                  }
> -                for(i = 0;i < gidsetsize; i++)
> +                for(i = 0;i < ret; i++)
>                      target_grouplist[i] = tswap32(grouplist[i]);
>                  unlock_user(target_grouplist, arg2, gidsetsize * 4);
>              }
> 
> It makes getgroups much faster in some cases.

Can anybody commit it?

-- 
Regards,  Kirill A. Shutemov
 + Belarus, Minsk
 + Velesys Ltd, http://www.velesys.com/
 + ALT Linux Team, http://www.altlinux.com/

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