linux-kernel - [RFC PATCH] iommu/amd: make kmemleak ignore the 'irq_remap

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Date:	Fri, 20 Nov 2015 12:09:30 +0100
From:	Michael Wang <yun.wang@...fitbricks.com>
To:	Joerg Roedel <joro@...tes.org>
Cc:	iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: [RFC PATCH] iommu/amd: make kmemleak ignore the 'irq_remap_table'
 object

The kmemleak testing on 3.18.24 show:

unreferenced object 0xffff880233ff9010 (size 16):
  comm "swapper/0", pid 1, jiffies 4294937440 (age 2010.490s)
  hex dump (first 16 bytes):
    0a 0a 00 00 20 00 00 00 00 44 fb 33 02 88 ff ff  .... ....D.3....
  backtrace:
    [<ffffffff8118192d>] create_object+0x10d/0x2d0
    [<ffffffff815c2d4b>] kmemleak_alloc+0x5b/0xc0
    [<ffffffff8116dd19>] kmem_cache_alloc_trace+0xb9/0x160
    [<ffffffff814ffe51>] get_irq_table+0x151/0x380

This is caused by the 'irq_lookup_table' was allocated with
__get_free_pages() which won't create kmemleak object, thus it's
pointers won't be count as referencing in kmemleak scanning.

The 'irq_remap_table' allocated won't be freed after initialized,
doesn't make sense to let kmemleak scan it.

This patch mark the 'irq_remap_table' object as 'ignored' to
stop the 'false positives' report.

Signed-off-by: Michael Wang <yun.wang@...fitbricks.com>
---
 drivers/iommu/amd_iommu.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
index 8b2be1e..87a1a88 100644
--- a/drivers/iommu/amd_iommu.c
+++ b/drivers/iommu/amd_iommu.c
@@ -3603,6 +3603,7 @@ static struct irq_remap_table *get_irq_table(u16 devid, bool ioapic)
 	}
 
 	irq_lookup_table[devid] = table;
+	kmemleak_ignore(table);
 	set_dte_irq_entry(devid, table);
 	iommu_flush_dte(iommu, devid);
 	if (devid != alias) {
-- 
2.1.4
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