Re: help-inode-watch error

[William Cohen <wcohen at redhat dot com>]

Kevin Jia wrote:
> inode-watch.stp  (in systemtap tutorial) source code:
>
> probe kernel.function ("vfs_write"),
>       kernel.function ("vfs_read")
> {
>         dev_nr = $file->f_dentry->d_inode->i_sb->s_dev
>         inode_nr = $file->f_dentry->d_inode->i_ino
>         if (dev_nr == ($1 << 20 | $2) && inode_nr == $3)
>         printf ("%s(%d) %s 0x%x/%u\n",
>         execname(), pid(), probefunc(), dev_nr, inode_nr)
> }
>
> but have errors about $1,$2,$3, the information:
>
> semantic error: unable to find local '1' near pc 0xc015b304:
> identifier '$1' at inode-watch.stp:7:17
> semantic error: unable to find local '2' near pc 0xc015b304:
> identifier '$2' at inode-watch.stp:7:28
> semantic error: unable to find local '3' near pc 0xc015b304:
> identifier '$3' at inode-watch.stp:7:47
> semantic error: due to failed target variable resolution
> semantic error: no match for probe point
>          while: resolving probe point kernel.function("vfs_write")
> semantic error: unable to find local '1' near pc 0xc015b096:
> identifier '$1' at inode-watch.stp:7:17
> semantic error: unable to find local '2' near pc 0xc015b096:
> identifier '$2' at inode-watch.stp:7:28
> semantic error: unable to find local '3' near pc 0xc015b096:
> identifier '$3' at inode-watch.stp:7:47
> semantic error: due to failed target variable resolution
> semantic error: no match for probe point
>          while: resolving probe point kernel.function("vfs_read")
> Pass 2: analysis failed.  Try again with '-v' (verbose) option.
>
> Why? Thank you.

Which version of systemtap are you using? It looks like the version of 
stap you are using is interpretting them as local variables. Do you have 
a relatively recent version of stap (one around mid march))? The $1, $2, 
and $3 refer to arguments on the command line. Take a look at the 
example in the tutorial and there are additional arguments on command line.

-Will