----- Original Message -----
>
>
> ----- Original Message -----
> >
> > Hi Dave
> >
> > I found a problem with the net -s command. It concerns line 1451 in net.c
> >
> > struct_socket = inode - SIZE(socket);
> >
> > As I understand it we have the type
> >
> > struct socket_alloc {
> > struct socket socket;
> > struct inode vfs_inode;
> > }
> >
> > and we have the address of the second field and want the address of
> > the first. The calculation, using the size of the socket struct,
> > used in net.c require that the second field is aligned directly
> > after the first field. This is unfortunately not true in cases I
> > have seen. By changing the line 1451 to:
> >
> > struct_socket = inode - MEMBER_OFFSET("socket_alloc", "vfs_inode");
> >
> > things work better.
> >
> > Is this something you would like to change in Crash? I assume you
> > will move the offset calculation to somewhere else so it is only
> > performed once.
>
> Probably so...
>
> Although I'm curious -- what kernel version do you see this on?
> It works as expected on RHEL5, RHEL6 and a Fedora 16 3.1.7-based
> kernel. What do you see when you do this:
>
> crash> socket_alloc -o
> struct socket_alloc {
> [0] struct socket socket;
> [48] struct inode vfs_inode;
> }
> SIZE: 616
> crash> socket
> struct socket {
> socket_state state;
> short int type;
> long unsigned int flags;
> struct socket_wq *wq;
> struct file *file;
> struct sock *sk;
> const struct proto_ops *ops;
> }
> SIZE: 48
> crash>
>
> And just for the changelog description, what havoc does it wreak?
>
> Thanks,
> Dave
Interesing -- I see the problem with the 3 sample ARM dumpfiles I have
on hand. I would have thought the same issue would be seen with
a 32-bit x86, but it looks like it's an ARM compiler issue?
Check this comparison -- while the inode structure is different in
these two kernels, the socket structure is the same:
X86: ARM:
crash> socket_alloc -o crash> socket_alloc -o
struct socket_alloc { struct socket_alloc {
[0] struct socket socket; [0] struct socket socket;
[28] struct inode vfs_inode; [32] struct inode vfs_inode;
} }
SIZE: 388 SIZE: 584
crash> socket -o crash> socket -o
struct socket { struct socket {
[0] socket_state state; [0] socket_state state;
[4] short int type; [4] short int type;
[8] long unsigned int flags; [8] long unsigned int flags;
[12] struct socket_wq *wq; [12] struct socket_wq *wq;
[16] struct file *file; [16] struct file *file;
[20] struct sock *sk; [20] struct sock *sk;
[24] const struct proto_ops *ops; [24] const struct proto_ops *ops;
} }
SIZE: 28 SIZE: 28
crash> crash>
But for whatever reason, the ARM kernel pushes the vfs_inode to
offset 32 even though the preceding socket structure is 28 bytes long.
Anyway, using the offset instead of the size is a better idea, so I'll
make that change.
Although -- my sample ARM dumpfiles don't have any tasks with open sockets,
so I still am interested in seeing what the failure looks like for the
changelog entry.
Thanks,
Dave
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