<feed xmlns='http://www.w3.org/2005/Atom'>
<title>linux-toradex.git/net/openvswitch/datapath.c, branch v4.14-rc5</title>
<subtitle>Linux kernel for Apalis and Colibri modules</subtitle>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/'/>
<entry>
<title>openvswitch: Fix an error handling path in 'ovs_nla_init_match_and_action()'</title>
<updated>2017-09-13T03:37:31+00:00</updated>
<author>
<name>Christophe JAILLET</name>
<email>christophe.jaillet@wanadoo.fr</email>
</author>
<published>2017-09-11T19:56:20+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=5829e62ac17a40ab08c1b905565604a4b5fa7af6'/>
<id>5829e62ac17a40ab08c1b905565604a4b5fa7af6</id>
<content type='text'>
All other error handling paths in this function go through the 'error'
label. This one should do the same.

Fixes: 9cc9a5cb176c ("datapath: Avoid using stack larger than 1024.")
Signed-off-by: Christophe JAILLET &lt;christophe.jaillet@wanadoo.fr&gt;
Acked-by: Pravin B Shelar &lt;pshelar@ovn.org&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
All other error handling paths in this function go through the 'error'
label. This one should do the same.

Fixes: 9cc9a5cb176c ("datapath: Avoid using stack larger than 1024.")
Signed-off-by: Christophe JAILLET &lt;christophe.jaillet@wanadoo.fr&gt;
Acked-by: Pravin B Shelar &lt;pshelar@ovn.org&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net</title>
<updated>2017-08-22T00:06:42+00:00</updated>
<author>
<name>David S. Miller</name>
<email>davem@davemloft.net</email>
</author>
<published>2017-08-22T00:06:42+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=e2a7c34fb2856fd5306e307e170e3dde358d0dce'/>
<id>e2a7c34fb2856fd5306e307e170e3dde358d0dce</id>
<content type='text'>
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
</pre>
</div>
</content>
</entry>
<entry>
<title>openvswitch: fix skb_panic due to the incorrect actions attrlen</title>
<updated>2017-08-16T21:12:37+00:00</updated>
<author>
<name>Liping Zhang</name>
<email>zlpnobody@gmail.com</email>
</author>
<published>2017-08-16T05:30:07+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=494bea39f3201776cdfddc232705f54a0bd210c4'/>
<id>494bea39f3201776cdfddc232705f54a0bd210c4</id>
<content type='text'>
For sw_flow_actions, the actions_len only represents the kernel part's
size, and when we dump the actions to the userspace, we will do the
convertions, so it's true size may become bigger than the actions_len.

But unfortunately, for OVS_PACKET_ATTR_ACTIONS, we use the actions_len
to alloc the skbuff, so the user_skb's size may become insufficient and
oops will happen like this:
  skbuff: skb_over_panic: text:ffffffff8148fabf len:1749 put:157 head:
  ffff881300f39000 data:ffff881300f39000 tail:0x6d5 end:0x6c0 dev:&lt;NULL&gt;
  ------------[ cut here ]------------
  kernel BUG at net/core/skbuff.c:129!
  [...]
  Call Trace:
   &lt;IRQ&gt;
   [&lt;ffffffff8148be82&gt;] skb_put+0x43/0x44
   [&lt;ffffffff8148fabf&gt;] skb_zerocopy+0x6c/0x1f4
   [&lt;ffffffffa0290d36&gt;] queue_userspace_packet+0x3a3/0x448 [openvswitch]
   [&lt;ffffffffa0292023&gt;] ovs_dp_upcall+0x30/0x5c [openvswitch]
   [&lt;ffffffffa028d435&gt;] output_userspace+0x132/0x158 [openvswitch]
   [&lt;ffffffffa01e6890&gt;] ? ip6_rcv_finish+0x74/0x77 [ipv6]
   [&lt;ffffffffa028e277&gt;] do_execute_actions+0xcc1/0xdc8 [openvswitch]
   [&lt;ffffffffa028e3f2&gt;] ovs_execute_actions+0x74/0x106 [openvswitch]
   [&lt;ffffffffa0292130&gt;] ovs_dp_process_packet+0xe1/0xfd [openvswitch]
   [&lt;ffffffffa0292b77&gt;] ? key_extract+0x63c/0x8d5 [openvswitch]
   [&lt;ffffffffa029848b&gt;] ovs_vport_receive+0xa1/0xc3 [openvswitch]
  [...]

Also we can find that the actions_len is much little than the orig_len:
  crash&gt; struct sw_flow_actions 0xffff8812f539d000
  struct sw_flow_actions {
    rcu = {
      next = 0xffff8812f5398800,
      func = 0xffffe3b00035db32
    },
    orig_len = 1384,
    actions_len = 592,
    actions = 0xffff8812f539d01c
  }

So as a quick fix, use the orig_len instead of the actions_len to alloc
the user_skb.

Last, this oops happened on our system running a relative old kernel, but
the same risk still exists on the mainline, since we use the wrong
actions_len from the beginning.

Fixes: ccea74457bbd ("openvswitch: include datapath actions with sampled-packet upcall to userspace")
Cc: Neil McKee &lt;neil.mckee@inmon.com&gt;
Signed-off-by: Liping Zhang &lt;zlpnobody@gmail.com&gt;
Acked-by: Pravin B Shelar &lt;pshelar@ovn.org&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
For sw_flow_actions, the actions_len only represents the kernel part's
size, and when we dump the actions to the userspace, we will do the
convertions, so it's true size may become bigger than the actions_len.

But unfortunately, for OVS_PACKET_ATTR_ACTIONS, we use the actions_len
to alloc the skbuff, so the user_skb's size may become insufficient and
oops will happen like this:
  skbuff: skb_over_panic: text:ffffffff8148fabf len:1749 put:157 head:
  ffff881300f39000 data:ffff881300f39000 tail:0x6d5 end:0x6c0 dev:&lt;NULL&gt;
  ------------[ cut here ]------------
  kernel BUG at net/core/skbuff.c:129!
  [...]
  Call Trace:
   &lt;IRQ&gt;
   [&lt;ffffffff8148be82&gt;] skb_put+0x43/0x44
   [&lt;ffffffff8148fabf&gt;] skb_zerocopy+0x6c/0x1f4
   [&lt;ffffffffa0290d36&gt;] queue_userspace_packet+0x3a3/0x448 [openvswitch]
   [&lt;ffffffffa0292023&gt;] ovs_dp_upcall+0x30/0x5c [openvswitch]
   [&lt;ffffffffa028d435&gt;] output_userspace+0x132/0x158 [openvswitch]
   [&lt;ffffffffa01e6890&gt;] ? ip6_rcv_finish+0x74/0x77 [ipv6]
   [&lt;ffffffffa028e277&gt;] do_execute_actions+0xcc1/0xdc8 [openvswitch]
   [&lt;ffffffffa028e3f2&gt;] ovs_execute_actions+0x74/0x106 [openvswitch]
   [&lt;ffffffffa0292130&gt;] ovs_dp_process_packet+0xe1/0xfd [openvswitch]
   [&lt;ffffffffa0292b77&gt;] ? key_extract+0x63c/0x8d5 [openvswitch]
   [&lt;ffffffffa029848b&gt;] ovs_vport_receive+0xa1/0xc3 [openvswitch]
  [...]

Also we can find that the actions_len is much little than the orig_len:
  crash&gt; struct sw_flow_actions 0xffff8812f539d000
  struct sw_flow_actions {
    rcu = {
      next = 0xffff8812f5398800,
      func = 0xffffe3b00035db32
    },
    orig_len = 1384,
    actions_len = 592,
    actions = 0xffff8812f539d01c
  }

So as a quick fix, use the orig_len instead of the actions_len to alloc
the user_skb.

Last, this oops happened on our system running a relative old kernel, but
the same risk still exists on the mainline, since we use the wrong
actions_len from the beginning.

Fixes: ccea74457bbd ("openvswitch: include datapath actions with sampled-packet upcall to userspace")
Cc: Neil McKee &lt;neil.mckee@inmon.com&gt;
Signed-off-by: Liping Zhang &lt;zlpnobody@gmail.com&gt;
Acked-by: Pravin B Shelar &lt;pshelar@ovn.org&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>net: Remove all references to SKB_GSO_UDP.</title>
<updated>2017-07-17T16:52:58+00:00</updated>
<author>
<name>David S. Miller</name>
<email>davem@davemloft.net</email>
</author>
<published>2017-07-03T14:29:12+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=880388aa3c07fdea4f9b85e35641753017b1852f'/>
<id>880388aa3c07fdea4f9b85e35641753017b1852f</id>
<content type='text'>
Such packets are no longer possible.

Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Such packets are no longer possible.

Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>datapath: Avoid using stack larger than 1024.</title>
<updated>2017-07-01T16:09:59+00:00</updated>
<author>
<name>Tonghao Zhang</name>
<email>xiangxia.m.yue@gmail.com</email>
</author>
<published>2017-06-30T00:27:44+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=9cc9a5cb176ccb4f2cda5ac34da5a659926f125f'/>
<id>9cc9a5cb176ccb4f2cda5ac34da5a659926f125f</id>
<content type='text'>
When compiling OvS-master on 4.4.0-81 kernel,
there is a warning:

    CC [M]  /root/ovs/datapath/linux/datapath.o
    /root/ovs/datapath/linux/datapath.c: In function
    'ovs_flow_cmd_set':
    /root/ovs/datapath/linux/datapath.c:1221:1: warning:
    the frame size of 1040 bytes is larger than 1024 bytes
    [-Wframe-larger-than=]

This patch factors out match-init and action-copy to avoid
"Wframe-larger-than=1024" warning. Because mask is only
used to get actions, we new a function to save some
stack space.

Signed-off-by: Tonghao Zhang &lt;xiangxia.m.yue@gmail.com&gt;
Acked-by: Pravin B Shelar &lt;pshelar@ovn.org&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
When compiling OvS-master on 4.4.0-81 kernel,
there is a warning:

    CC [M]  /root/ovs/datapath/linux/datapath.o
    /root/ovs/datapath/linux/datapath.c: In function
    'ovs_flow_cmd_set':
    /root/ovs/datapath/linux/datapath.c:1221:1: warning:
    the frame size of 1040 bytes is larger than 1024 bytes
    [-Wframe-larger-than=]

This patch factors out match-init and action-copy to avoid
"Wframe-larger-than=1024" warning. Because mask is only
used to get actions, we new a function to save some
stack space.

Signed-off-by: Tonghao Zhang &lt;xiangxia.m.yue@gmail.com&gt;
Acked-by: Pravin B Shelar &lt;pshelar@ovn.org&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>networking: convert many more places to skb_put_zero()</title>
<updated>2017-06-16T15:48:35+00:00</updated>
<author>
<name>Johannes Berg</name>
<email>johannes.berg@intel.com</email>
</author>
<published>2017-06-16T12:29:19+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=b080db585384b9f037e015c0c28d1ad33be41dfc'/>
<id>b080db585384b9f037e015c0c28d1ad33be41dfc</id>
<content type='text'>
There were many places that my previous spatch didn't find,
as pointed out by yuan linyu in various patches.

The following spatch found many more and also removes the
now unnecessary casts:

    @@
    identifier p, p2;
    expression len;
    expression skb;
    type t, t2;
    @@
    (
    -p = skb_put(skb, len);
    +p = skb_put_zero(skb, len);
    |
    -p = (t)skb_put(skb, len);
    +p = skb_put_zero(skb, len);
    )
    ... when != p
    (
    p2 = (t2)p;
    -memset(p2, 0, len);
    |
    -memset(p, 0, len);
    )

    @@
    type t, t2;
    identifier p, p2;
    expression skb;
    @@
    t *p;
    ...
    (
    -p = skb_put(skb, sizeof(t));
    +p = skb_put_zero(skb, sizeof(t));
    |
    -p = (t *)skb_put(skb, sizeof(t));
    +p = skb_put_zero(skb, sizeof(t));
    )
    ... when != p
    (
    p2 = (t2)p;
    -memset(p2, 0, sizeof(*p));
    |
    -memset(p, 0, sizeof(*p));
    )

    @@
    expression skb, len;
    @@
    -memset(skb_put(skb, len), 0, len);
    +skb_put_zero(skb, len);

Apply it to the tree (with one manual fixup to keep the
comment in vxlan.c, which spatch removed.)

Signed-off-by: Johannes Berg &lt;johannes.berg@intel.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
There were many places that my previous spatch didn't find,
as pointed out by yuan linyu in various patches.

The following spatch found many more and also removes the
now unnecessary casts:

    @@
    identifier p, p2;
    expression len;
    expression skb;
    type t, t2;
    @@
    (
    -p = skb_put(skb, len);
    +p = skb_put_zero(skb, len);
    |
    -p = (t)skb_put(skb, len);
    +p = skb_put_zero(skb, len);
    )
    ... when != p
    (
    p2 = (t2)p;
    -memset(p2, 0, len);
    |
    -memset(p, 0, len);
    )

    @@
    type t, t2;
    identifier p, p2;
    expression skb;
    @@
    t *p;
    ...
    (
    -p = skb_put(skb, sizeof(t));
    +p = skb_put_zero(skb, sizeof(t));
    |
    -p = (t *)skb_put(skb, sizeof(t));
    +p = skb_put_zero(skb, sizeof(t));
    )
    ... when != p
    (
    p2 = (t2)p;
    -memset(p2, 0, sizeof(*p));
    |
    -memset(p, 0, sizeof(*p));
    )

    @@
    expression skb, len;
    @@
    -memset(skb_put(skb, len), 0, len);
    +skb_put_zero(skb, len);

Apply it to the tree (with one manual fixup to keep the
comment in vxlan.c, which spatch removed.)

Signed-off-by: Johannes Berg &lt;johannes.berg@intel.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>openvswitch: more accurate checksumming in queue_userspace_packet()</title>
<updated>2017-05-19T23:21:29+00:00</updated>
<author>
<name>Davide Caratti</name>
<email>dcaratti@redhat.com</email>
</author>
<published>2017-05-18T13:44:42+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=7529390d08f07fbf9b0174c5a87600b5caa1a8e8'/>
<id>7529390d08f07fbf9b0174c5a87600b5caa1a8e8</id>
<content type='text'>
if skb carries an SCTP packet and ip_summed is CHECKSUM_PARTIAL, it needs
CRC32c in place of Internet Checksum: use skb_csum_hwoffload_help to avoid
corrupting such packets while queueing them towards userspace.

Signed-off-by: Davide Caratti &lt;dcaratti@redhat.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
if skb carries an SCTP packet and ip_summed is CHECKSUM_PARTIAL, it needs
CRC32c in place of Internet Checksum: use skb_csum_hwoffload_help to avoid
corrupting such packets while queueing them towards userspace.

Signed-off-by: Davide Caratti &lt;dcaratti@redhat.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>netlink: pass extended ACK struct to parsing functions</title>
<updated>2017-04-13T17:58:22+00:00</updated>
<author>
<name>Johannes Berg</name>
<email>johannes.berg@intel.com</email>
</author>
<published>2017-04-12T12:34:07+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=fceb6435e85298f747fee938415057af837f5a8a'/>
<id>fceb6435e85298f747fee938415057af837f5a8a</id>
<content type='text'>
Pass the new extended ACK reporting struct to all of the generic
netlink parsing functions. For now, pass NULL in almost all callers
(except for some in the core.)

Signed-off-by: Johannes Berg &lt;johannes.berg@intel.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Pass the new extended ACK reporting struct to all of the generic
netlink parsing functions. For now, pass NULL in almost all callers
(except for some in the core.)

Signed-off-by: Johannes Berg &lt;johannes.berg@intel.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>openvswitch: upcall: Fix vlan handling.</title>
<updated>2016-12-27T17:28:07+00:00</updated>
<author>
<name>pravin shelar</name>
<email>pshelar@ovn.org</email>
</author>
<published>2016-12-26T16:31:27+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=df30f7408b187929dbde72661c7f7c615268f1d0'/>
<id>df30f7408b187929dbde72661c7f7c615268f1d0</id>
<content type='text'>
Networking stack accelerate vlan tag handling by
keeping topmost vlan header in skb. This works as
long as packet remains in OVS datapath. But during
OVS upcall vlan header is pushed on to the packet.
When such packet is sent back to OVS datapath, core
networking stack might not handle it correctly. Following
patch avoids this issue by accelerating the vlan tag
during flow key extract. This simplifies datapath by
bringing uniform packet processing for packets from
all code paths.

Fixes: 5108bbaddc ("openvswitch: add processing of L3 packets").
CC: Jarno Rajahalme &lt;jarno@ovn.org&gt;
CC: Jiri Benc &lt;jbenc@redhat.com&gt;
Signed-off-by: Pravin B Shelar &lt;pshelar@ovn.org&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Networking stack accelerate vlan tag handling by
keeping topmost vlan header in skb. This works as
long as packet remains in OVS datapath. But during
OVS upcall vlan header is pushed on to the packet.
When such packet is sent back to OVS datapath, core
networking stack might not handle it correctly. Following
patch avoids this issue by accelerating the vlan tag
during flow key extract. This simplifies datapath by
bringing uniform packet processing for packets from
all code paths.

Fixes: 5108bbaddc ("openvswitch: add processing of L3 packets").
CC: Jarno Rajahalme &lt;jarno@ovn.org&gt;
CC: Jiri Benc &lt;jbenc@redhat.com&gt;
Signed-off-by: Pravin B Shelar &lt;pshelar@ovn.org&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>netns: make struct pernet_operations::id unsigned int</title>
<updated>2016-11-18T15:59:15+00:00</updated>
<author>
<name>Alexey Dobriyan</name>
<email>adobriyan@gmail.com</email>
</author>
<published>2016-11-17T01:58:21+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=c7d03a00b56fc23c3a01a8353789ad257363e281'/>
<id>c7d03a00b56fc23c3a01a8353789ad257363e281</id>
<content type='text'>
Make struct pernet_operations::id unsigned.

There are 2 reasons to do so:

1)
This field is really an index into an zero based array and
thus is unsigned entity. Using negative value is out-of-bound
access by definition.

2)
On x86_64 unsigned 32-bit data which are mixed with pointers
via array indexing or offsets added or subtracted to pointers
are preffered to signed 32-bit data.

"int" being used as an array index needs to be sign-extended
to 64-bit before being used.

	void f(long *p, int i)
	{
		g(p[i]);
	}

  roughly translates to

	movsx	rsi, esi
	mov	rdi, [rsi+...]
	call 	g

MOVSX is 3 byte instruction which isn't necessary if the variable is
unsigned because x86_64 is zero extending by default.

Now, there is net_generic() function which, you guessed it right, uses
"int" as an array index:

	static inline void *net_generic(const struct net *net, int id)
	{
		...
		ptr = ng-&gt;ptr[id - 1];
		...
	}

And this function is used a lot, so those sign extensions add up.

Patch snipes ~1730 bytes on allyesconfig kernel (without all junk
messing with code generation):

	add/remove: 0/0 grow/shrink: 70/598 up/down: 396/-2126 (-1730)

Unfortunately some functions actually grow bigger.
This is a semmingly random artefact of code generation with register
allocator being used differently. gcc decides that some variable
needs to live in new r8+ registers and every access now requires REX
prefix. Or it is shifted into r12, so [r12+0] addressing mode has to be
used which is longer than [r8]

However, overall balance is in negative direction:

	add/remove: 0/0 grow/shrink: 70/598 up/down: 396/-2126 (-1730)
	function                                     old     new   delta
	nfsd4_lock                                  3886    3959     +73
	tipc_link_build_proto_msg                   1096    1140     +44
	mac80211_hwsim_new_radio                    2776    2808     +32
	tipc_mon_rcv                                1032    1058     +26
	svcauth_gss_legacy_init                     1413    1429     +16
	tipc_bcbase_select_primary                   379     392     +13
	nfsd4_exchange_id                           1247    1260     +13
	nfsd4_setclientid_confirm                    782     793     +11
		...
	put_client_renew_locked                      494     480     -14
	ip_set_sockfn_get                            730     716     -14
	geneve_sock_add                              829     813     -16
	nfsd4_sequence_done                          721     703     -18
	nlmclnt_lookup_host                          708     686     -22
	nfsd4_lockt                                 1085    1063     -22
	nfs_get_client                              1077    1050     -27
	tcf_bpf_init                                1106    1076     -30
	nfsd4_encode_fattr                          5997    5930     -67
	Total: Before=154856051, After=154854321, chg -0.00%

Signed-off-by: Alexey Dobriyan &lt;adobriyan@gmail.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Make struct pernet_operations::id unsigned.

There are 2 reasons to do so:

1)
This field is really an index into an zero based array and
thus is unsigned entity. Using negative value is out-of-bound
access by definition.

2)
On x86_64 unsigned 32-bit data which are mixed with pointers
via array indexing or offsets added or subtracted to pointers
are preffered to signed 32-bit data.

"int" being used as an array index needs to be sign-extended
to 64-bit before being used.

	void f(long *p, int i)
	{
		g(p[i]);
	}

  roughly translates to

	movsx	rsi, esi
	mov	rdi, [rsi+...]
	call 	g

MOVSX is 3 byte instruction which isn't necessary if the variable is
unsigned because x86_64 is zero extending by default.

Now, there is net_generic() function which, you guessed it right, uses
"int" as an array index:

	static inline void *net_generic(const struct net *net, int id)
	{
		...
		ptr = ng-&gt;ptr[id - 1];
		...
	}

And this function is used a lot, so those sign extensions add up.

Patch snipes ~1730 bytes on allyesconfig kernel (without all junk
messing with code generation):

	add/remove: 0/0 grow/shrink: 70/598 up/down: 396/-2126 (-1730)

Unfortunately some functions actually grow bigger.
This is a semmingly random artefact of code generation with register
allocator being used differently. gcc decides that some variable
needs to live in new r8+ registers and every access now requires REX
prefix. Or it is shifted into r12, so [r12+0] addressing mode has to be
used which is longer than [r8]

However, overall balance is in negative direction:

	add/remove: 0/0 grow/shrink: 70/598 up/down: 396/-2126 (-1730)
	function                                     old     new   delta
	nfsd4_lock                                  3886    3959     +73
	tipc_link_build_proto_msg                   1096    1140     +44
	mac80211_hwsim_new_radio                    2776    2808     +32
	tipc_mon_rcv                                1032    1058     +26
	svcauth_gss_legacy_init                     1413    1429     +16
	tipc_bcbase_select_primary                   379     392     +13
	nfsd4_exchange_id                           1247    1260     +13
	nfsd4_setclientid_confirm                    782     793     +11
		...
	put_client_renew_locked                      494     480     -14
	ip_set_sockfn_get                            730     716     -14
	geneve_sock_add                              829     813     -16
	nfsd4_sequence_done                          721     703     -18
	nlmclnt_lookup_host                          708     686     -22
	nfsd4_lockt                                 1085    1063     -22
	nfs_get_client                              1077    1050     -27
	tcf_bpf_init                                1106    1076     -30
	nfsd4_encode_fattr                          5997    5930     -67
	Total: Before=154856051, After=154854321, chg -0.00%

Signed-off-by: Alexey Dobriyan &lt;adobriyan@gmail.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</pre>
</div>
</content>
</entry>
</feed>
