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taskstats: use the libnl API to align nlattr on 64-bit

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Goal of this patch is to use the new libnl API to align netlink attribute
when needed.
The layout of the netlink message will be a bit different after the patch,
because the padattr (TASKSTATS_TYPE_STATS) will be inside the nested
attribute instead of before it.

Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Nicolas Dichtel 2016-04-22 17:31:24 +02:00 committed by David S. Miller
parent de95c4a46a
commit 80df554275
1 changed files with 5 additions and 32 deletions
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37
kernel/taskstats.c
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@ -357,10 +357,6 @@ static int parse(struct nlattr *na, struct cpumask *mask)
return ret;
}
#if defined(CONFIG_64BIT) && !defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
#define TASKSTATS_NEEDS_PADDING 1
#endif
static struct taskstats *mk_reply(struct sk_buff *skb, int type, u32 pid)
{
struct nlattr *na, *ret;
@ -370,29 +366,6 @@ static struct taskstats *mk_reply(struct sk_buff *skb, int type, u32 pid)
? TASKSTATS_TYPE_AGGR_PID
: TASKSTATS_TYPE_AGGR_TGID;
/*
* The taskstats structure is internally aligned on 8 byte
* boundaries but the layout of the aggregrate reply, with
* two NLA headers and the pid (each 4 bytes), actually
* force the entire structure to be unaligned. This causes
* the kernel to issue unaligned access warnings on some
* architectures like ia64. Unfortunately, some software out there
* doesn't properly unroll the NLA packet and assumes that the start
* of the taskstats structure will always be 20 bytes from the start
* of the netlink payload. Aligning the start of the taskstats
* structure breaks this software, which we don't want. So, for now
* the alignment only happens on architectures that require it
* and those users will have to update to fixed versions of those
* packages. Space is reserved in the packet only when needed.
* This ifdef should be removed in several years e.g. 2012 once
* we can be confident that fixed versions are installed on most
* systems. We add the padding before the aggregate since the
* aggregate is already a defined type.
*/
#ifdef TASKSTATS_NEEDS_PADDING
if (nla_put(skb, TASKSTATS_TYPE_NULL, 0, NULL) < 0)
goto err;
#endif
na = nla_nest_start(skb, aggr);
if (!na)
goto err;
@ -401,7 +374,8 @@ static struct taskstats *mk_reply(struct sk_buff *skb, int type, u32 pid)
nla_nest_cancel(skb, na);
goto err;
}
ret = nla_reserve(skb, TASKSTATS_TYPE_STATS, sizeof(struct taskstats));
ret = nla_reserve_64bit(skb, TASKSTATS_TYPE_STATS,
sizeof(struct taskstats), TASKSTATS_TYPE_NULL);
if (!ret) {
nla_nest_cancel(skb, na);
goto err;
@ -500,10 +474,9 @@ static size_t taskstats_packet_size(void)
size_t size;
size = nla_total_size(sizeof(u32)) +
nla_total_size(sizeof(struct taskstats)) + nla_total_size(0);
#ifdef TASKSTATS_NEEDS_PADDING
size += nla_total_size(0); /* Padding for alignment */
#endif
nla_total_size_64bit(sizeof(struct taskstats)) +
nla_total_size(0);
return size;
}