Re: [Qemu-devel] [PATCH v6 4/8] linux-user/syscall: Introduce target_sockaddr_nl

[Laurent Vivier <laurent@vivier.eu>]

Le 11/09/2019 à 21:34, Philippe Mathieu-Daudé a écrit :
> On Mon, Sep 9, 2019 at 4:23 PM Laurent Vivier <laurent@vivier.eu> wrote:
>> Le 08/09/2019 à 08:15, Philippe Mathieu-Daudé a écrit :
>>> Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
>>> Tested-By: Guido Günther <agx@sigxcpu.org>
>>> ---
>>>  linux-user/syscall.c      | 6 ++++--
>>>  linux-user/syscall_defs.h | 7 +++++++
>>>  2 files changed, 11 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/linux-user/syscall.c b/linux-user/syscall.c
>>> index 8b41a03901..5128312db5 100644
>>> --- a/linux-user/syscall.c
>>> +++ b/linux-user/syscall.c
>>> @@ -1494,8 +1494,10 @@ static inline abi_long host_to_target_sockaddr(abi_ulong target_addr,
>>>          sizeof(target_saddr->sa_family)) {
>>>          target_saddr->sa_family = tswap16(addr->sa_family);
>>>      }
>>> -    if (addr->sa_family == AF_NETLINK && len >= sizeof(struct sockaddr_nl)) {
>>> -        struct sockaddr_nl *target_nl = (struct sockaddr_nl *)target_saddr;
>>> +    if (addr->sa_family == AF_NETLINK &&
>>> +        len >= sizeof(struct target_sockaddr_nl)) {
>>> +        struct target_sockaddr_nl *target_nl =
>>> +               (struct target_sockaddr_nl *)target_saddr;
>>>          target_nl->nl_pid = tswap32(target_nl->nl_pid);
>>>          target_nl->nl_groups = tswap32(target_nl->nl_groups);
>>>      } else if (addr->sa_family == AF_PACKET) {
>>> diff --git a/linux-user/syscall_defs.h b/linux-user/syscall_defs.h
>>> index 0662270300..fcedd0d0fb 100644
>>> --- a/linux-user/syscall_defs.h
>>> +++ b/linux-user/syscall_defs.h
>>> @@ -153,6 +153,13 @@ struct target_sockaddr_un {
>>>      uint8_t sun_path[108];
>>>  };
>>>
>>> +struct target_sockaddr_nl {
>>> +    uint16_t nl_family;     /* AF_NETLINK */
>>> +    uint16_t __pad;
>>> +    uint32_t nl_pid;
>>> +    uint32_t nl_groups;
>>> +};
>>
>> You should use abi_ushort and abi_uint to keep alignments good (for
>> instance m68k aligns on 16bit whereas others on 32bit).
> 
> Are you sure? The other target_sockaddr don't use that...
> Is this because netlink is a host-only structure? (while other are
> serialized over some interface).

I think other target_sockaddr are wrong too. No one takes really care of
alignment, and most of the time structures are by construction well aligned.

Thanks,
Laurent