Re: seq_file: procfs: kmalloc_slab WARNING

[Wladislav Wiebe <wladislav.kw@gmail.com>]

Hi Andrew,

On 29/08/13 23:54, Andrew Morton wrote:
> On Tue, 06 Aug 2013 15:26:23 +0200 Wladislav Wiebe <wladislav.kw@gmail.com> wrote:
> 
> [..]
> kmalloc_large() only exists in slub, so this will break slab and slob
> builds.
> 
> Did you try adding __GFP_NOWARN?  That's appropriate in this case.
> 

Thanks for the reply, I already committed the fix for the real problem in 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@gmail.com>
---
 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