[Bug translator/10820] New: stap -L should take varaible location list into account

[Bug translator/10820] New: stap -L should take varaible location list into account

[mjw at redhat dot com]

Sometimes you believe a variable is available with -L, but then it turns out the
location list for that variable doesn't actually cover the address that we will
place the probe on.

For example:

$ stap -L 'kernel.function("tc_fill_tclass")'
kernel.function("tc_fill_tclass@net/sched/sch_api.c:990") $skb:struct sk_buff*
$q:struct Qdisc* $cl:long unsigned int $pid:u32 $seq:u32 $flags:u16 $event:int
$tcm:struct tcmsg* $nlh:struct nlmsghdr* $b:unsigned char* $d:struct gnet_dump
$cl_ops:struct Qdisc_class_ops*

But then when we try to actually query $tcm we get:
semantic error: not accessible at this address (0xffffffff80239505): identifier
'$tcm' at <input>:1:96
         source: probe kernel.function("tc_fill_tclass").return {
printf("pid=%d, cl=%d, tcm=%p.\n", $pid, $cl, $tcm-) }

Which is indeed correct, the location list for tcm says:

     0048393a ffffffff802395a2 ffffffff80239643 (DW_OP_reg6)
     0048393a ffffffff802396aa ffffffff80239719 (DW_OP_reg6)

So it isn't available at the (function entry) probe address.

-- 
           Summary: stap -L should take varaible location list into account
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: translator
        AssignedTo: systemtap at sources dot redhat dot com
        ReportedBy: mjw at redhat dot com


http://sourceware.org/bugzilla/show_bug.cgi?id=10820

------- You are receiving this mail because: -------
You are the assignee for the bug, or are watching the assignee.

[Bug translator/10820] stap -L should take varaible location list into account

[eteo at redhat dot com]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |eteo at redhat dot com


http://sourceware.org/bugzilla/show_bug.cgi?id=10820

------- You are receiving this mail because: -------
You are the assignee for the bug, or are watching the assignee.

[Bug translator/10820] stap -L should take varaible location list into account

[wenji dot huang at oracle dot com]

------- Additional Comments From wenji dot huang at oracle dot com  2009-10-28 08:08 -------
Created an attachment (id=4332)
 --> (http://sourceware.org/bugzilla/attachment.cgi?id=4332&action=view)
patch and example

With this patch,

$ stap -L 'kernel.function("tc_fill_tclass")'
kernel.function("tc_fill_tclass@net/sched/sch_api.c:1435") $skb:struct sk_buff*
$q:struct Qdisc* $cl:long unsigned int $pid:u32 $seq:u32 $flags:u16 $event:int
$nlh:struct nlmsghdr* $b:unsigned char* $cl_ops:struct Qdisc_class_ops const*

We can see $tcm and $d are eliminated. And to access the listed variables,
$ stap -p4 -e 'probe
kernel.function("tc_fill_tclass"){print($skb+$q+$cl+$pid+$seq+$flags+$event+$nlh+$b+$cl_ops)}'

stap_16232.ko

-- 


http://sourceware.org/bugzilla/show_bug.cgi?id=10820

------- You are receiving this mail because: -------
You are the assignee for the bug, or are watching the assignee.

[Bug translator/10820] stap -L should take varaible location list into account

[fche at redhat dot com]

------- Additional Comments From fche at redhat dot com  2009-10-28 16:49 -------
Looks good to me, please commit, unless jistone has objections.

-- 


http://sourceware.org/bugzilla/show_bug.cgi?id=10820

------- You are receiving this mail because: -------
You are the assignee for the bug, or are watching the assignee.

[Bug translator/10820] stap -L should take varaible location list into account

[jistone at redhat dot com]

------- Additional Comments From jistone at redhat dot com  2009-10-28 18:16 -------
Looks fine to me too, thanks!

-- 


http://sourceware.org/bugzilla/show_bug.cgi?id=10820

------- You are receiving this mail because: -------
You are the assignee for the bug, or are watching the assignee.

[Bug translator/10820] stap -L should take varaible location list into account

[wenji dot huang at oracle dot com]

------- Additional Comments From wenji dot huang at oracle dot com  2009-10-29 00:34 -------
commit	f10534c6a2a958609b7bc76390d50c17a36250d3

-- 


http://sourceware.org/bugzilla/show_bug.cgi?id=10820

------- You are receiving this mail because: -------
You are the assignee for the bug, or are watching the assignee.

[Bug translator/10820] stap -L should take varaible location list into account

[fche at redhat dot com]

------- Additional Comments From fche at redhat dot com  2009-10-29 01:41 -------
thanks!

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED


http://sourceware.org/bugzilla/show_bug.cgi?id=10820

------- You are receiving this mail because: -------
You are the assignee for the bug, or are watching the assignee.