63 lines
2.2 KiB
Plaintext
63 lines
2.2 KiB
Plaintext
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From: Jeff Mahoney <jeffm@suse.com>
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Subject: [PATCH] delayacct: align to 8 byte boundary on 64-bit systems
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References: bnc#578065
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Patch-mainline: Hopefully 2.6.34, submitting when the window opens
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prepare_reply sets up an skb for the response. If I understand it correctly,
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the payload contains:
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+--------------------------------+
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| genlmsghdr - 4 bytes |
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+--------------------------------+
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| NLA header - 4 bytes | /* Aggregate header */
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+-+------------------------------+
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| | NLA header - 4 bytes | /* PID header */
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| +------------------------------+
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| | pid/tgid - 4 bytes |
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| +------------------------------+
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| | NLA header - 4 bytes | /* stats header */
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| + -----------------------------+ <- oops. aligned on 4 byte boundary
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| | struct taskstats - 328 bytes |
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+-+------------------------------+
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The start of the taskstats struct must be 8 byte aligned on IA64 (and other
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systems with 8 byte alignment rules for 64-bit types) or runtime alignment
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warnings will be issued.
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This patch pads the pid/tgid field out to sizeof(long), which forces
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the alignment of taskstats. The getdelays userspace code is ok with this
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since it assumes 32-bit pid/tgid and then honors that header's length field.
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An array is used to avoid exposing kernel memory contents to userspace in the
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response.
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Signed-off-by: Jeff Mahoney <jeffm@suse.com>
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---
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kernel/taskstats.c | 8 +++++++-
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1 file changed, 7 insertions(+), 1 deletion(-)
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--- a/kernel/taskstats.c
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+++ b/kernel/taskstats.c
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@@ -359,6 +359,12 @@ static struct taskstats *mk_reply(struct
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struct nlattr *na, *ret;
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int aggr;
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+ /* If we don't pad, we end up with alignment on a 4 byte boundary.
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+ * This causes lots of runtime warnings on systems requiring 8 byte
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+ * alignment */
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+ u32 pids[2] = { pid, 0 };
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+ int pid_size = ALIGN(sizeof(pid), sizeof(long));
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+
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aggr = (type == TASKSTATS_TYPE_PID)
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? TASKSTATS_TYPE_AGGR_PID
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: TASKSTATS_TYPE_AGGR_TGID;
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@@ -366,7 +372,7 @@ static struct taskstats *mk_reply(struct
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na = nla_nest_start(skb, aggr);
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if (!na)
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goto err;
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- if (nla_put(skb, type, sizeof(pid), &pid) < 0)
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+ if (nla_put(skb, type, pid_size, pids) < 0)
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goto err;
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ret = nla_reserve(skb, TASKSTATS_TYPE_STATS, sizeof(struct taskstats));
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if (!ret)
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