Re: [Qemu-devel] [12/16] linux-user: support {name_to, open_by}_handle_at syscalls

[Paul Burton]

On Tue, Aug 26, 2014 at 03:30:41PM +0300, Riku Voipio wrote:
> Hi Paul,
> 
> On Sun, Jun 15, 2014 at 05:18:29PM +0100, Paul Burton wrote:
> > Implement support for the name_to_handle_at and open_by_handle_at
> > syscalls, allowing their use by the target program. 
> 
> What was your testcase for these syscalls? I usually use LTP for testing
> syscalls, but there is no testcase for name_to_handle_at and
> open_by_handle_at.

Hi Riku,

First thanks for taking care of a whole bunch of these patches, and my
apologies for not being around or responsive! Meatspace has been keeping
me busy, but has calmed down for now so I should be able to find more
time to contribute :)

Actually my test for these was that a mipsel systemd could boot from
init through to a login prompt inside a container on my x86-64 host
using QEMU via binfmt_misc. That does however also require a few more
patches which I need to clean up before submitting. But you can find
them here in the short term if you're interested:

  https://github.com/Arch-Linux-MIPS/qemu

Paul

> Riku
> 
> > Signed-off-by: Paul Burton <address@hidden>
> > ---
> >  linux-user/strace.c    | 30 ++++++++++++++++++++++++++++++
> >  linux-user/strace.list |  6 ++++++
> >  linux-user/syscall.c   | 50 
> > ++++++++++++++++++++++++++++++++++++++++++++++++++
> >  3 files changed, 86 insertions(+)
> > 
> > diff --git a/linux-user/strace.c b/linux-user/strace.c
> > index ea6c1d2..c20ddf1 100644
> > --- a/linux-user/strace.c
> > +++ b/linux-user/strace.c
> > @@ -1552,6 +1552,36 @@ print_kill(const struct syscallname *name,
> >  }
> >  #endif
> >  
> > +#ifdef TARGET_NR_name_to_handle_at
> > +static void
> > +print_name_to_handle_at(const struct syscallname *name,
> > +    abi_long arg0, abi_long arg1, abi_long arg2,
> > +    abi_long arg3, abi_long arg4, abi_long arg5)
> > +{
> > +    print_syscall_prologue(name);
> > +    print_at_dirfd(arg0, 0);
> > +    print_string(arg1, 0);
> > +    print_pointer(arg2, 0);
> > +    print_pointer(arg3, 0);
> > +    print_raw_param("0x%x", arg4, 1);
> > +    print_syscall_epilogue(name);
> > +}
> > +#endif
> > +
> > +#ifdef TARGET_NR_open_by_handle_at
> > +static void
> > +print_open_by_handle_at(const struct syscallname *name,
> > +    abi_long arg0, abi_long arg1, abi_long arg2,
> > +    abi_long arg3, abi_long arg4, abi_long arg5)
> > +{
> > +    print_syscall_prologue(name);
> > +    print_raw_param("%d", arg0, 0);
> > +    print_pointer(arg2, 0);
> > +    print_open_flags(arg3, 1);
> > +    print_syscall_epilogue(name);
> > +}
> > +#endif
> > +
> >  /*
> >   * An array of all of the syscalls we know about
> >   */
> > diff --git a/linux-user/strace.list b/linux-user/strace.list
> > index 8de972a..147f579 100644
> > --- a/linux-user/strace.list
> > +++ b/linux-user/strace.list
> > @@ -582,6 +582,9 @@
> >  #ifdef TARGET_NR_munmap
> >  { TARGET_NR_munmap, "munmap" , NULL, print_munmap, NULL },
> >  #endif
> > +#ifdef TARGET_NR_name_to_handle_at
> > +{ TARGET_NR_name_to_handle_at, "name_to_handle_at" , NULL, 
> > print_name_to_handle_at, NULL },
> > +#endif
> >  #ifdef TARGET_NR_nanosleep
> >  { TARGET_NR_nanosleep, "nanosleep" , NULL, NULL, NULL },
> >  #endif
> > @@ -624,6 +627,9 @@
> >  #ifdef TARGET_NR_openat
> >  { TARGET_NR_openat, "openat" , NULL, print_openat, NULL },
> >  #endif
> > +#ifdef TARGET_NR_open_by_handle_at
> > +{ TARGET_NR_open_by_handle_at, "open_by_handle_at" , NULL, 
> > print_open_by_handle_at, NULL },
> > +#endif
> >  #ifdef TARGET_NR_osf_adjtime
> >  { TARGET_NR_osf_adjtime, "osf_adjtime" , NULL, NULL, NULL },
> >  #endif
> > diff --git a/linux-user/syscall.c b/linux-user/syscall.c
> > index c7f176a..192ad3a 100644
> > --- a/linux-user/syscall.c
> > +++ b/linux-user/syscall.c
> > @@ -5349,6 +5349,56 @@ abi_long do_syscall(void *cpu_env, int num, abi_long 
> > arg1,
> >          unlock_user(p, arg2, 0);
> >          break;
> >  #endif
> > +#ifdef TARGET_NR_name_to_handle_at
> > +    case TARGET_NR_name_to_handle_at:
> > +        {
> > +            struct file_handle *fh;
> > +            uint32_t sz;
> > +            int mount_id;
> > +
> > +            if (!(p = lock_user_string(arg2)))
> > +                goto efault;
> > +
> > +            if (get_user_u32(sz, arg3)) {
> > +                unlock_user(p, arg2, 0);
> > +                goto efault;
> > +            }
> > +
> > +            if (!(fh = lock_user(VERIFY_WRITE, arg3, sizeof(*fh) + sz, 
> > 1))) {
> > +                unlock_user(p, arg2, 0);
> > +                goto efault;
> > +            }
> > +
> > +            ret = get_errno(name_to_handle_at(arg1, path(p), fh,
> > +                                              &mount_id, arg5));
> > +
> > +            unlock_user(p, arg2, 0);
> > +            unlock_user(p, arg3, sizeof(*fh) + sz);
> > +
> > +            if (put_user_s32(mount_id, arg4))
> > +                goto efault;
> > +        }
> > +        break;
> > +#endif
> > +#ifdef TARGET_NR_open_by_handle_at
> > +    case TARGET_NR_open_by_handle_at:
> > +        {
> > +            struct file_handle *fh;
> > +            uint32_t sz;
> > +
> > +            if (get_user_u32(sz, arg2))
> > +                goto efault;
> > +
> > +            if (!(fh = lock_user(VERIFY_WRITE, arg2, sizeof(*fh) + sz, 1)))
> > +                goto efault;
> > +
> > +            ret = get_errno(open_by_handle_at(arg1, fh,
> > +                    target_to_host_bitmask(arg3, fcntl_flags_tbl)));
> > +
> > +            unlock_user(p, arg2, sizeof(*fh) + sz);
> > +        }
> > +        break;
> > +#endif
> >      case TARGET_NR_close:
> >          ret = get_errno(close(arg1));
> >          break;

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