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Commit 80df5542 authored by Nicolas Dichtel's avatar Nicolas Dichtel Committed by David S. Miller
Browse files

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



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: default avatarNicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent de95c4a4

kernel/taskstats.c

+5 −32
Original line number Diff line number Diff line
@@ -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;

}