Hi guys,
we got the real root cause of the allocation issue:
Subject: [PATCH 1/1] of: fdt: fix memory initialization for expanded DT
Already existing property flags are filled wrong for properties created from
initial FDT. This could cause problems if this DYNAMIC device-tree functions
are used later, i.e. properties are attached/detached/replaced. Simply dumping
flags from the running system show, that some initial static (not allocated via
kzmalloc()) nodes are marked as dynamic.
I putted some debug extensions to property_proc_show(..) :
..
+ if (OF_IS_DYNAMIC(pp))
+ pr_err("DEBUG: xxx : OF_IS_DYNAMIC\n");
+ if (OF_IS_DETACHED(pp))
+ pr_err("DEBUG: xxx : OF_IS_DETACHED\n");
when you operate on the nodes (e.g.: ~$ cat /proc/device-tree/*some_node*) you
will see that those flags are filled wrong, basically in most cases it will dump
a DYNAMIC or DETACHED status, which is in not true.
(BTW. this OF_IS_DETACHED is a own define for debug purposes which which just
make a test_bit(OF_DETACHED, &x->_flags)
If nodes are dynamic kernel is allowed to kfree() them. But it will crash
attempting to do so on the nodes from FDT -- they are not allocated via
kzmalloc().
Signed-off-by: Wladislav Wiebe <wladislav.kw@xxxxxxxxx>
---
drivers/of/fdt.c | 2 ++
1 files changed, 2 insertions(+), 0 deletions(-)
diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index 6bb7cf2..b10ba00 100644
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -392,6 +392,8 @@ static void __unflatten_device_tree(struct boot_param_header *blob,
mem = (unsigned long)
dt_alloc(size + 4, __alignof__(struct device_node));
+ memset((void *)mem, 0, size);
+
((__be32 *)mem)[size / 4] = cpu_to_be32(0xdeadbeef);
pr_debug(" unflattening %lx...\n", mem);
-- 1.7.1
This is committed to the mainline - hope it comes in soon.
Thanks & BR,
Wladislav Wiebe
On 31/07/13 19:34, Aaro Koskinen wrote:
> Hi,
>
> On Wed, Jul 31, 2013 at 01:42:31PM +0200, Wladislav Wiebe wrote:
>> DEBUG: xxx kmalloc_slab, requested 'size' = 8388608, KMALLOC_MAX_SIZE = 4194304
> [...]
>> [ccd3be60] [c0099fd4] kmalloc_slab+0x48/0xe8 (unreliable)
>> [ccd3be70] [c00ae650] __kmalloc+0x20/0x1b4
>> [ccd3be90] [c00d46f4] seq_read+0x2a4/0x540
>> [ccd3bee0] [c00fe09c] proc_reg_read+0x5c/0x90
>> [ccd3bef0] [c00b4e1c] vfs_read+0xa4/0x150
>> [ccd3bf10] [c00b500c] SyS_read+0x4c/0x84
>> [ccd3bf40] [c000be80] ret_from_syscall+0x0/0x3c
>
> It seems some procfs file is trying to dump 8 MB at a single go. You
> need to fix that to return data in smaller chunks. What file is it?
>
> A.
>
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