[Crash-utility] display function parameters for call stack

[Lei Wen]

On Mon, Sep 24, 2012 at 9:30 PM, Dave Anderson <anderson at redhat.com> wrote:

>
>
> ----- Original Message -----
> >
> > Dave,
> >
> >
> > On Fri, Sep 21, 2012 at 9:44 PM, Dave Anderson < anderson at redhat.com
> > > wrote:
> >
> >
> >
> >
> >
> > ----- Original Message -----
> > >
> > > Hi Dave,
> > >
> > >
> > > I notice there was some discussion around on enabling
> > > the display function parameters feature for crash tool.
> > > Like this one:
> > > http://www.redhat.com/archives/crash-utility/2009-May/msg00016.html
> >
> > Yes, it seems to come up every few years. People have tried, but it
> > has never come to fruition.
> >
> >
> > >
> > > Although the answer seems to be quite clear, it should be hard to
> > > support such feature. But does this feature cannot be done anyway?
> > > I think this feature would be great in assisting kernel debug.
> > >
> > > The main feature I require, first should be know each param's value in
> the call stack.
> > > Then it is better to know each call stack's param's name.
> > >
> > > Like for do_vfs_ioctl function, it is better to display as:
> > > do_vfs_ioctl(filp=xxx, fd=xxx, cmd=xxx, arg=xxx)
> > >
> > > Do you have any idea on how this could be implemented?
> >
> > No I don't.
> >
> >
> >
> > Sorry for asking the stupid question, but I notice that we could
> > get the structure member in crash by "struct" command:
> >
> > crash> struct stackframe
> > struct stackframe {
> > long unsigned int fp;
> > long unsigned int sp;
> > long unsigned int lr;
> > long unsigned int pc;
> > }
> > SIZE: 16
> >
> >
> > I check the crash code, and find cmd_struct use gdb interface to
> > parse it out.
> >
> >
> > And the gdb itself seems already could parse out function argument[1],
> so could
> > we still use similar mechanism as the "struct" command to implement a
> "func"
> > command, which could shows the function declaration?
>
> You can either use the "whatis" command to get the function declaration:
>
>  crash> help whatis
>
>  NAME
>    whatis - search symbol table for data or type information
>
>  SYNOPSIS
>    whatis [struct | union | typedef | symbol]
>
>  DESCRIPTION
>    This command displays the definition of structures, unions, typedefs or
>    text/data symbols.
>  ...
>
>
>  crash> whatis do_vfs_ioctl
>  int do_vfs_ioctl(struct file *, unsigned int, unsigned int, long unsigned
> int);
>  crash>
>
> Or print it with "p", which gives you both the declaration and its virtual
> address:
>
>  crash> p do_vfs_ioctl
>  do_vfs_ioctl = $14 =
>   {int (struct file *, unsigned int, unsigned int, long unsigned int)}
> 0xffffffff811247ec <do_vfs_ioctl>
>  crash>
>
>
That works. :)
However could it be possible to show the argument without only display its
type?
The kernel is defining the do_vfs_ioctl as:
int do_vfs_ioctl(struct file *filp, unsigned int fd, unsigned int cmd,
             unsigned long arg);
Could the "filp, fd, cmd, arg" be showed out?


> Dave
>
>
Thanks,
Lei
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