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Re: [Qemu-devel] [PATCH v2] linux-user: improve target_to_host_sock_type


From: Petar Jovanovic
Subject: Re: [Qemu-devel] [PATCH v2] linux-user: improve target_to_host_sock_type conversion
Date: Tue, 7 May 2013 23:16:03 +0000

ping

http://patchwork.ozlabs.org/patch/232770/
________________________________________
From: Petar Jovanovic
Sent: Tuesday, April 30, 2013 3:20 AM
To: Andreas Färber
Cc: Aurelien Jarno; Petar Jovanovic; address@hidden; address@hidden; 
address@hidden; address@hidden; Alexander Graf
Subject: RE: [Qemu-devel] [PATCH v2] linux-user: improve 
target_to_host_sock_type conversion

My assumption was that if new socket values are added in future, they will
likely be the same for all platforms, so they can be supported without
adding new lines of code. Here we convert the values known to be different,
we leave the values known to be the same, and for the incorrect values - we
pass them to (host) kernel as they are in belief that kernel would return
error. We could handle that part and check for incorrect value before
passing it to the kernel, but in that case we bring more kernel logic to
QEMU for the cases that are not likely to happen.

Petar
________________________________________
From: Andreas Färber address@hidden
Sent: Monday, April 29, 2013 4:56 PM
To: Petar Jovanovic
Cc: Aurelien Jarno; Petar Jovanovic; address@hidden; address@hidden; 
address@hidden; address@hidden; Alexander Graf
Subject: Re: [Qemu-devel] [PATCH v2] linux-user: improve 
target_to_host_sock_type conversion

Am 23.04.2013 02:15, schrieb Petar Jovanovic:
> Thanks Aurelien for your comments.
>
> What others think? Can we submit this version of the patch? Riku? Richard, 
> Blue?

No objection but isn't that a frequent issue that mappings may need to
be extended from time to time? The way I've seen that handled is on a
case by case basis mapping from one known value to another, with
defaulting to whatever form of error reporting appropriate. Here it
seems that some cases were dropped and we are now defaulting to taking
the literal value where no difference is known. This may lead to silent
errors, whereas an abort as other extreme may prohibit use cases with no
value difference between host and target.

Andreas

> ________________________________________
> From: Aurelien Jarno address@hidden
> Sent: Monday, April 15, 2013 3:47 PM
> To: Petar Jovanovic
> Cc: address@hidden; Petar Jovanovic; address@hidden; address@hidden; 
> address@hidden
> Subject: Re: [PATCH v2] linux-user: improve target_to_host_sock_type 
> conversion
>
> On Mon, Apr 01, 2013 at 05:49:39PM +0200, Petar Jovanovic wrote:
>> From: Petar Jovanovic <address@hidden>
>>
>> Previous implementation has failed to take into account different value of
>> SOCK_NONBLOCK on target and host, and existence of SOCK_CLOEXEC.
>> The same conversion has to be applied both for do_socket and do_socketpair,
>> so the code has been isolated in a static inline function.
>> The change is valid for architectures that define ARCH_HAS_SOCKET_TYPES,
>> these are MIPS, SPARC and ALPHA now.
>>
>> enum sock_type in linux-user/socket.h has been extended to include
>> TARGET_SOCK_CLOEXEC and TARGET_SOCK_NONBLOCK, similar to definition in libc.
>> The patch also includes necessary code style changes (tab to spaces) in the
>> header file in the MIPS #ifdef block touched by the change.
>>
>> Signed-off-by: Petar Jovanovic <address@hidden>
>> ---
>>  v2:
>>
>>  - the patch defines ARCH_HAS_SOCKET_TYPES for MIPS, SPARC and ALPHA
>>  - values for sock_type are defined for SPARC and ALPHA in socket.h
>>
>>  linux-user/socket.h  |  248 
>> +++++++++++++++++++++++++++++++++-----------------
>>  linux-user/syscall.c |   45 +++++----
>>  2 files changed, 195 insertions(+), 98 deletions(-)
>>
>> diff --git a/linux-user/socket.h b/linux-user/socket.h
>> index 339cae5..d2b05dc 100644
>> --- a/linux-user/socket.h
>> +++ b/linux-user/socket.h
>> @@ -1,91 +1,104 @@
>>
>>  #if defined(TARGET_MIPS)
>> -     // MIPS special values for constants
>> -
>> -     /*
>> -      * For setsockopt(2)
>> -      *
>> -      * This defines are ABI conformant as far as Linux supports these ...
>> -      */
>> -     #define TARGET_SOL_SOCKET      0xffff
>> -
>> -     #define TARGET_SO_DEBUG        0x0001  /* Record debugging 
>> information.  */
>> -     #define TARGET_SO_REUSEADDR    0x0004  /* Allow reuse of local 
>> addresses.  */
>> -     #define TARGET_SO_KEEPALIVE    0x0008  /* Keep connections alive and 
>> send
>> -                                       SIGPIPE when they die.  */
>> -     #define TARGET_SO_DONTROUTE    0x0010  /* Don't do local routing.  */
>> -     #define TARGET_SO_BROADCAST    0x0020  /* Allow transmission of
>> -                                       broadcast messages.  */
>> -     #define TARGET_SO_LINGER       0x0080  /* Block on close of a reliable
>> -                                       socket to transmit pending data.  */
>> -     #define TARGET_SO_OOBINLINE 0x0100     /* Receive out-of-band data 
>> in-band.  */
>> -     #if 0
>> -     To add: #define TARGET_SO_REUSEPORT 0x0200     /* Allow local address 
>> and port reuse.  */
>> -     #endif
>> -
>> -     #define TARGET_SO_TYPE         0x1008  /* Compatible name for 
>> SO_STYLE.  */
>> -     #define TARGET_SO_STYLE        SO_TYPE /* Synonym */
>> -     #define TARGET_SO_ERROR        0x1007  /* get error status and clear */
>> -     #define TARGET_SO_SNDBUF       0x1001  /* Send buffer size. */
>> -     #define TARGET_SO_RCVBUF       0x1002  /* Receive buffer. */
>> -     #define TARGET_SO_SNDLOWAT     0x1003  /* send low-water mark */
>> -     #define TARGET_SO_RCVLOWAT     0x1004  /* receive low-water mark */
>> -     #define TARGET_SO_SNDTIMEO     0x1005  /* send timeout */
>> -     #define TARGET_SO_RCVTIMEO     0x1006  /* receive timeout */
>> -     #define TARGET_SO_ACCEPTCONN   0x1009
>> -
>> -     /* linux-specific, might as well be the same as on i386 */
>> -     #define TARGET_SO_NO_CHECK     11
>> -     #define TARGET_SO_PRIORITY     12
>> -     #define TARGET_SO_BSDCOMPAT    14
>> +    /* MIPS special values for constants */
>> +
>> +    /*
>> +     * For setsockopt(2)
>> +     *
>> +     * This defines are ABI conformant as far as Linux supports these ...
>> +     */
>> +    #define TARGET_SOL_SOCKET      0xffff
>> +
>> +    #define TARGET_SO_DEBUG        0x0001  /* Record debugging information. 
>> */
>> +    #define TARGET_SO_REUSEADDR    0x0004  /* Allow reuse of local 
>> addresses. */
>> +    #define TARGET_SO_KEEPALIVE    0x0008  /* Keep connections alive and 
>> send
>> +                                              SIGPIPE when they die. */
>> +    #define TARGET_SO_DONTROUTE    0x0010  /* Don't do local routing. */
>> +    #define TARGET_SO_BROADCAST    0x0020  /* Allow transmission of
>> +                                              broadcast messages. */
>> +    #define TARGET_SO_LINGER       0x0080  /* Block on close of a reliable
>> +                                            * socket to transmit pending 
>> data.
>> +                                            */
>> +    #define TARGET_SO_OOBINLINE 0x0100     /* Receive out-of-band data 
>> in-band.
>> +                                            */
>> +    #if 0
>> +    /* To add: Allow local address and port reuse. */
>> +    #define TARGET_SO_REUSEPORT 0x0200
>> +    #endif
>> +
>> +    #define TARGET_SO_TYPE         0x1008  /* Compatible name for SO_STYLE. 
>> */
>> +    #define TARGET_SO_STYLE        SO_TYPE /* Synonym */
>> +    #define TARGET_SO_ERROR        0x1007  /* get error status and clear */
>> +    #define TARGET_SO_SNDBUF       0x1001  /* Send buffer size. */
>> +    #define TARGET_SO_RCVBUF       0x1002  /* Receive buffer. */
>> +    #define TARGET_SO_SNDLOWAT     0x1003  /* send low-water mark */
>> +    #define TARGET_SO_RCVLOWAT     0x1004  /* receive low-water mark */
>> +    #define TARGET_SO_SNDTIMEO     0x1005  /* send timeout */
>> +    #define TARGET_SO_RCVTIMEO     0x1006  /* receive timeout */
>> +    #define TARGET_SO_ACCEPTCONN   0x1009
>>
>> -     #define TARGET_SO_PASSCRED     17
>> -     #define TARGET_SO_PEERCRED     18
>> +    /* linux-specific, might as well be the same as on i386 */
>> +    #define TARGET_SO_NO_CHECK     11
>> +    #define TARGET_SO_PRIORITY     12
>> +    #define TARGET_SO_BSDCOMPAT    14
>>
>> -     /* Security levels - as per NRL IPv6 - don't actually do anything */
>> -     #define TARGET_SO_SECURITY_AUTHENTICATION              22
>> -     #define TARGET_SO_SECURITY_ENCRYPTION_TRANSPORT        23
>> -     #define TARGET_SO_SECURITY_ENCRYPTION_NETWORK          24
>> +    #define TARGET_SO_PASSCRED     17
>> +    #define TARGET_SO_PEERCRED     18
>>
>> -     #define TARGET_SO_BINDTODEVICE         25
>> +    /* Security levels - as per NRL IPv6 - don't actually do anything */
>> +    #define TARGET_SO_SECURITY_AUTHENTICATION              22
>> +    #define TARGET_SO_SECURITY_ENCRYPTION_TRANSPORT        23
>> +    #define TARGET_SO_SECURITY_ENCRYPTION_NETWORK          24
>>
>> -     /* Socket filtering */
>> -     #define TARGET_SO_ATTACH_FILTER        26
>> -     #define TARGET_SO_DETACH_FILTER        27
>> +    #define TARGET_SO_BINDTODEVICE         25
>>
>> -     #define TARGET_SO_PEERNAME             28
>> -     #define TARGET_SO_TIMESTAMP            29
>> -     #define SCM_TIMESTAMP          SO_TIMESTAMP
>> -
>> -     #define TARGET_SO_PEERSEC              30
>> -     #define TARGET_SO_SNDBUFFORCE          31
>> -     #define TARGET_SO_RCVBUFFORCE          33
>> -
>> -     /** sock_type - Socket types
>> -      *
>> -      * Please notice that for binary compat reasons MIPS has to
>> -      * override the enum sock_type in include/linux/net.h, so
>> -      * we define ARCH_HAS_SOCKET_TYPES here.
>> -      *
>> -      * @SOCK_DGRAM - datagram (conn.less) socket
>> -      * @SOCK_STREAM - stream (connection) socket
>> -      * @SOCK_RAW - raw socket
>> -      * @SOCK_RDM - reliably-delivered message
>> -      * @SOCK_SEQPACKET - sequential packet socket
>> -      * @SOCK_PACKET - linux specific way of getting packets at the dev 
>> level.
>> -      *               For writing rarp and other similar things on the user 
>> level.
>> -      */
>> -     enum sock_type {
>> -            TARGET_SOCK_DGRAM       = 1,
>> -            TARGET_SOCK_STREAM      = 2,
>> -            TARGET_SOCK_RAW = 3,
>> -            TARGET_SOCK_RDM = 4,
>> -            TARGET_SOCK_SEQPACKET   = 5,
>> -            TARGET_SOCK_DCCP        = 6,
>> -            TARGET_SOCK_PACKET      = 10,
>> -     };
>> -
>> -     #define TARGET_SOCK_MAX (SOCK_PACKET + 1)
>> +    /* Socket filtering */
>> +    #define TARGET_SO_ATTACH_FILTER        26
>> +    #define TARGET_SO_DETACH_FILTER        27
>> +
>> +    #define TARGET_SO_PEERNAME             28
>> +    #define TARGET_SO_TIMESTAMP            29
>> +    #define SCM_TIMESTAMP          SO_TIMESTAMP
>> +
>> +    #define TARGET_SO_PEERSEC              30
>> +    #define TARGET_SO_SNDBUFFORCE          31
>> +    #define TARGET_SO_RCVBUFFORCE          33
>> +
>> +    /** sock_type - Socket types
>> +     *
>> +     * Please notice that for binary compat reasons MIPS has to
>> +     * override the enum sock_type in include/linux/net.h, so
>> +     * we define ARCH_HAS_SOCKET_TYPES here.
>> +     *
>> +     * @SOCK_DGRAM - datagram (conn.less) socket
>> +     * @SOCK_STREAM - stream (connection) socket
>> +     * @SOCK_RAW - raw socket
>> +     * @SOCK_RDM - reliably-delivered message
>> +     * @SOCK_SEQPACKET - sequential packet socket
>> +     * @SOCK_DCCP - Datagram Congestion Control Protocol socket
>> +     * @SOCK_PACKET - linux specific way of getting packets at the dev 
>> level.
>> +     *                For writing rarp and other similar things on the user
>> +     *                level.
>> +     * @SOCK_CLOEXEC - sets the close-on-exec (FD_CLOEXEC) flag.
>> +     * @SOCK_NONBLOCK - sets the O_NONBLOCK file status flag.
>> +     */
>> +
>> +    #define ARCH_HAS_SOCKET_TYPES          1
>> +
>> +    enum sock_type {
>> +           TARGET_SOCK_DGRAM       = 1,
>> +           TARGET_SOCK_STREAM      = 2,
>> +           TARGET_SOCK_RAW         = 3,
>> +           TARGET_SOCK_RDM         = 4,
>> +           TARGET_SOCK_SEQPACKET   = 5,
>> +           TARGET_SOCK_DCCP        = 6,
>> +           TARGET_SOCK_PACKET      = 10,
>> +           TARGET_SOCK_CLOEXEC     = 02000000,
>> +           TARGET_SOCK_NONBLOCK    = 0200,
>> +    };
>> +
>> +    #define TARGET_SOCK_MAX (TARGET_SOCK_PACKET + 1)
>> +    #define TARGET_SOCK_TYPE_MASK    0xf  /* Covers up to 
>> TARGET_SOCK_MAX-1. */
>>
>>  #elif defined(TARGET_ALPHA)
>>
>> @@ -156,8 +169,81 @@
>>      /* Instruct lower device to use last 4-bytes of skb data as FCS */
>>      #define TARGET_SO_NOFCS     43
>>
>> +    /** sock_type - Socket types
>> +     *
>> +     * Please notice that for binary compat reasons ALPHA has to
>> +     * override the enum sock_type in include/linux/net.h, so
>> +     * we define ARCH_HAS_SOCKET_TYPES here.
>> +     *
>> +     * @SOCK_DGRAM - datagram (conn.less) socket
>> +     * @SOCK_STREAM - stream (connection) socket
>> +     * @SOCK_RAW - raw socket
>> +     * @SOCK_RDM - reliably-delivered message
>> +     * @SOCK_SEQPACKET - sequential packet socket
>> +     * @SOCK_DCCP - Datagram Congestion Control Protocol socket
>> +     * @SOCK_PACKET - linux specific way of getting packets at the dev 
>> level.
>> +     *                For writing rarp and other similar things on the user
>> +     *                level.
>> +     * @SOCK_CLOEXEC - sets the close-on-exec (FD_CLOEXEC) flag.
>> +     * @SOCK_NONBLOCK - sets the O_NONBLOCK file status flag.
>> +     */
>> +
>> +    #define ARCH_HAS_SOCKET_TYPES          1
>> +
>> +    enum sock_type {
>> +           TARGET_SOCK_STREAM      = 1,
>> +           TARGET_SOCK_DGRAM       = 2,
>> +           TARGET_SOCK_RAW         = 3,
>> +           TARGET_SOCK_RDM         = 4,
>> +           TARGET_SOCK_SEQPACKET   = 5,
>> +           TARGET_SOCK_DCCP        = 6,
>> +           TARGET_SOCK_PACKET      = 10,
>> +           TARGET_SOCK_CLOEXEC     = 010000000,
>> +           TARGET_SOCK_NONBLOCK    = 010000000000,
>> +    };
>> +
>> +    #define TARGET_SOCK_MAX (TARGET_SOCK_PACKET + 1)
>> +    #define TARGET_SOCK_TYPE_MASK    0xf  /* Covers up to 
>> TARGET_SOCK_MAX-1. */
>>  #else
>>
>> +#if defined(TARGET_SPARC)
>> +    /** sock_type - Socket types
>> +     *
>> +     * Please notice that for binary compat reasons SPARC has to
>> +     * override the enum sock_type in include/linux/net.h, so
>> +     * we define ARCH_HAS_SOCKET_TYPES here.
>> +     *
>> +     * @SOCK_DGRAM - datagram (conn.less) socket
>> +     * @SOCK_STREAM - stream (connection) socket
>> +     * @SOCK_RAW - raw socket
>> +     * @SOCK_RDM - reliably-delivered message
>> +     * @SOCK_SEQPACKET - sequential packet socket
>> +     * @SOCK_DCCP - Datagram Congestion Control Protocol socket
>> +     * @SOCK_PACKET - linux specific way of getting packets at the dev 
>> level.
>> +     *                For writing rarp and other similar things on the user
>> +     *                level.
>> +     * @SOCK_CLOEXEC - sets the close-on-exec (FD_CLOEXEC) flag.
>> +     * @SOCK_NONBLOCK - sets the O_NONBLOCK file status flag.
>> +     */
>> +
>> +    #define ARCH_HAS_SOCKET_TYPES          1
>> +
>> +    enum sock_type {
>> +           TARGET_SOCK_STREAM      = 1,
>> +           TARGET_SOCK_DGRAM       = 2,
>> +           TARGET_SOCK_RAW         = 3,
>> +           TARGET_SOCK_RDM         = 4,
>> +           TARGET_SOCK_SEQPACKET   = 5,
>> +           TARGET_SOCK_DCCP        = 6,
>> +           TARGET_SOCK_PACKET      = 10,
>> +           TARGET_SOCK_CLOEXEC     = 020000000,
>> +           TARGET_SOCK_NONBLOCK    = 040000,
>> +    };
>> +
>> +    #define TARGET_SOCK_MAX (TARGET_SOCK_PACKET + 1)
>> +    #define TARGET_SOCK_TYPE_MASK    0xf  /* Covers up to 
>> TARGET_SOCK_MAX-1. */
>> +#endif
>> +
>>       /* For setsockopt(2) */
>>       #define TARGET_SOL_SOCKET      1
>>
>> diff --git a/linux-user/syscall.c b/linux-user/syscall.c
>> index ee82a2d..5b87c9d 100644
>> --- a/linux-user/syscall.c
>> +++ b/linux-user/syscall.c
>> @@ -1859,30 +1859,38 @@ static void unlock_iovec(struct iovec *vec, 
>> abi_ulong target_addr,
>>      free(vec);
>>  }
>>
>> -/* do_socket() Must return target values and target errnos. */
>> -static abi_long do_socket(int domain, int type, int protocol)
>> +#if defined(ARCH_HAS_SOCKET_TYPES)
>> +static inline void target_to_host_sock_type(int *type)
>>  {
>> -#if defined(TARGET_MIPS)
>> -    switch(type) {
>> +    int host_type = 0;
>> +    int target_type = *type;
>> +
>> +    switch (target_type & TARGET_SOCK_TYPE_MASK) {
>>      case TARGET_SOCK_DGRAM:
>> -        type = SOCK_DGRAM;
>> +        host_type = SOCK_DGRAM;
>>          break;
>>      case TARGET_SOCK_STREAM:
>> -        type = SOCK_STREAM;
>> -        break;
>> -    case TARGET_SOCK_RAW:
>> -        type = SOCK_RAW;
>> +        host_type = SOCK_STREAM;
>>          break;
>> -    case TARGET_SOCK_RDM:
>> -        type = SOCK_RDM;
>> -        break;
>> -    case TARGET_SOCK_SEQPACKET:
>> -        type = SOCK_SEQPACKET;
>> -        break;
>> -    case TARGET_SOCK_PACKET:
>> -        type = SOCK_PACKET;
>> +    default:
>> +        host_type = target_type & TARGET_SOCK_TYPE_MASK;
>>          break;
>>      }
>> +    if (target_type & TARGET_SOCK_CLOEXEC) {
>> +        host_type |= SOCK_CLOEXEC;
>> +    }
>> +    if (target_type & TARGET_SOCK_NONBLOCK) {
>> +        host_type |= SOCK_NONBLOCK;
>> +    }
>> +    *type = host_type;
>
> The problem I see with this way of handling the flags is that if the
> kernel later adds a new flag value, QEMU will silently drop it. It means
> that if the glibc tries to see it will think the kernel (and here QEMU)
> supports it (as no error is returned), and will not use to the fallback
> code. For that each processed flag should probably be removed from
> target_type and it should be 0 at the end of the function.
>
> Imagine for example SOCK_NONBLOCK is a new feature, it starts to be
> supported by the glibc, but silently dropped by QEMU.
>
> That said I agree it's purely hypothetical, as no new flags has been
> added recently or is planned to be added. We can also decide to fix that
> when a new flag is added. What the other people (the Cc:ed one) think?
>
>> +}
>> +#endif
>> +
>> +/* do_socket() Must return target values and target errnos. */
>> +static abi_long do_socket(int domain, int type, int protocol)
>> +{
>> +#if defined(ARCH_HAS_SOCKET_TYPES)
>> +    target_to_host_sock_type(&type);
>>  #endif
>>      if (domain == PF_NETLINK)
>>          return -EAFNOSUPPORT; /* do not NETLINK socket connections possible 
>> */
>> @@ -2116,6 +2124,9 @@ static abi_long do_socketpair(int domain, int type, 
>> int protocol,
>>      int tab[2];
>>      abi_long ret;
>>
>> +#if defined(ARCH_HAS_SOCKET_TYPES)
>> +    target_to_host_sock_type(&type);
>> +#endif
>>      ret = get_errno(socketpair(domain, type, protocol, tab));
>>      if (!is_error(ret)) {
>>          if (put_user_s32(tab[0], target_tab_addr)
>
> Otherwise the patch looks fine.
>
>
> --
> Aurelien Jarno                          GPG: 1024D/F1BCDB73
> address@hidden                 http://www.aurel32.net
>
>


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