Re: [Crash-utility] Adding a new command rbtree
At 2012-5-22 4:21, Dave Anderson wrote:
----- Original Message -----
> The patch has been modified.
Whereas the radix_tree problem I showed in my last email seems to
be RHEL5-related, I cannot dump a red-black tree from an rb_root on
RHEL5, RHEL6 or Fedora.
I didn't explain the address clearly.
<cut>
The meaning of the "start" argument, which can be expressed either
symbolically or in hexadecimal format, depends upon whether the -N
option is pre-pended or not:
start The address of the structure where radix_tree_root(radix
tree) or rb_node(red-black tree) is embeded.
-N start The address of the structure radix_tree_node(radix tree)
or rb_node(red-black tree)
<cut>
So you can only specified rb_node's related address. The following is
about why the command doesn't support your situation.
In your situation, the offset you offered is the offset of rb_root.
struct rb_root
{
struct rb_node *rb_node;
};
So I can get the address of root node, then get the address of its
offspring nodes. But now, I cannot convert the address of an
rb_node(offspring node) to its related structure's information. In
details, the rb_node may be embeded in a structure, but the offset of
rb_node is not offered. So the offset should be the offset of rb_node.
For example, taking an mm_struct, it has an "mm_rb" rb_root:
crash> mm_struct.mm_rb
struct mm_struct {
[0x8] struct rb_root mm_rb;
}
Therefore I should be able to dump it with:
crash> tree -t rb -o mm_struct.mm_rb<mm-struct-address>
I get the mm_struct address like so:
crash> vm
PID: 20739 TASK: ffff8100190330c0 CPU: 3 COMMAND: "crash"
MM PGD RSS TOTAL_VM
ffff81003ceaeb00 ffff810023f9f000 111452k 190736k
...
But it always fails like this on RHEL5:
crash> tree -t rb -o mm_struct.mm_rb ffff81003ceaeb00
ffff81003ceaeb08
ffffffff8006fe65
6508ec8348f38948
tree: invalid kernel virtual address: 6508ec8348f38958 type: "rb_node
rb_left"
crash>
The same thing happens on RHEL6:
crash> vm
PID: 14353 TASK: ffff88003a93c080 CPU: 3 COMMAND: "crash"
MM PGD RSS TOTAL_VM
ffff880037b65840 ffff88001c31b000 153552k 288936k
...
crash> tree -t rb -o mm_struct.mm_rb ffff880037b65840
ffff880037b65848
ffffffff81010800
f075894ce86d894c
tree: invalid kernel virtual address: f075894ce86d895c type: "rb_node
rb_left"
crash>
And on a Fedora 3.3.1-3.fc16 kernel:
crash> vm
PID: 1175 TASK: ffff88003acb9730 CPU: 2 COMMAND: "crash"
MM PGD RSS TOTAL_VM
ffff880038495c00 ffff88003ac5a000 181580k 335436k
...
crash> tree -t rb -o mm_struct.mm_rb ffff880038495c00
ffff880038495c08
ffffffff81018ce0
f075894ce86d894c
tree: invalid kernel virtual address: f075894ce86d895c type: "rb_node
rb_left"
crash>
What's going on there?
Dave
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Regards
Qiao Nuohan