On Wed, Sep 20, 2017 at 09:57:00AM +0530, Nayan Gadre wrote:
> Hi,
>
> I have managed to do few things. @Jim and @Mathew inputs were helpful. Thanks
>
> So i have
> [root@vcssx247-ldm7 ~]#dtrace -lvn fbt:my_mod:msg_recv1:entry
> ID PROVIDER MODULE FUNCTION NAME
> 7090 fbt mymod msg_recv1 entry
>
> Probe Description Attributes
> Identifier Names: Private
> Data Semantics: Private
> Dependency Class: Unknown
>
> Argument Attributes
> Identifier Names: Private
> Data Semantics: Private
> Dependency Class: ISA
>
> Argument Types
> args[0]: mblk_t *
> args[1]: uint_t
> args[2]: uchar_t *
> args[3]: ulong_t
>
> And my probe then becomes:
> dtrace -n 'msg_recv1:entry { printf("msg_recv1: %x, %x\n",
> *(uchar_t*)args[0]->b_rptr, *((uchar_t*)args[0]->b_rptr + 1)); }'
>
> Now, the args[0]->b_rptr points to my custom structure pkt_hdr_t { }.
>
> Is is possible to typecast this args[0]->b_rptr to struct pkt_hdr_t *
> in the dtrace script for better readable access of the private
> structure variables instead of using offsets to b_rptr:
>
> Something like this:
> struct pkt_hdr_t* ppkt = (struct pkt_hdr_t*)args[0]->b_rptr;
>
> Then printf("%d\n", ppkt->member1);
In general, local variables to a probe are created and accessed using
this->varname. So you can easily store b_rptr in ppkt:
this->ppkt = args[0]->b_rptr;
But this will just use the type of b_rptr, so you'll still
need to cast stuff; you can put a cast before it, and then
the variable will be of that type.
In general, once you reach a certain complexity, a dtrace script is
easier to deal with. Your above code would look like:
% cat > myscript.d <<\EOF
#!/usr/sbin/dtrace -s
msg_recv1:entry {
this->ppkt = (uchar_t *)args[0]->b_rptr;
printf("msg_recv1: %x, %x\n", *this->ppkt, *(this->ppkt + 1));
}
EOF
% chmod +x myscript.d
If your module has CTF data (which would require you to change your build
process, and is not well documented), you could do:
% cat > myscript.d <<\EOF
#!/usr/sbin/dtrace -s
msg_recv1:entry {
this->ppkt = (struct pkt_hdr_t *)args[0]->b_rptr;
printf("msg_recv1: %x, %x\n", this->ppkt->foo, this->ppkt->bar);
}
EOF
% chmod +x myscript.d
You can also just define the structure in your script, or #include your
headers, using the -C arg to invoke the preprocessor:
(note the "struct C`struct_name" syntax; it makes sure you get the definitions
from the headers)
% cat > myscript.d <<\EOF
#!/usr/sbin/dtrace -Cs
#include "my_header.h"
msg_recv1:entry {
this->ppkt = (struct C`pkt_hdr_t *)args[0]->b_rptr;
printf("msg_recv1: %x, %x\n", this->ppkt->foo, this->ppkt->bar);
}
EOF
% chmod +x myscript.d
Cheers,
- jonathan
> Regards
>
> On Wed, Sep 20, 2017 at 12:13 AM, jim mauro <jim.ma...@gmail.com> wrote:
> > It's been a while (2+ years), but...
> >
> > The fbt provider makes function args available at entry probes via
> > args[0] ... args[n]. This are typed.
> >
> > So you should be able to dereference structure members of sk_buff
> > doing 'args[0]->structure_member', etc, when fbt:mymod:msg_recv:entry
> > fires....
> >
> > args[1] will be the link value
> > args[2] will be the src pointer.
> >
> > (jeez...I hope I'm remember this correctly. There was a book....).
> >
> > Thanks
> > Jim
> >
> >
> > On Tue, Sep 19, 2017 at 6:00 AM, Nayan Gadre <beejoy.na...@gmail.com> wrote:
> >>
> >> Hi,
> >>
> >> I am new to solaris dtrace debugging tool, but I have prior experience
> >> with Linux SystemTap.
> >>
> >> I need to debug my Solaris kernel module particularly extract the data
> >> in a structure passed by reference to my kernel function.
> >>
> >> msg_recv(struct sk_buff *skbp, uint_t link, uchar_t* src)
> >> {
> >> pkt_hdr_t *pkt;
> >> pkt = (pkt_hdr_t *)skbp->data;
> >> port = pkt->port;
> >> }
> >>
> >> I have written a systemtap script in linux to access the argument and
> >> extract data.
> >>
> >> How can I do this using DTRACE for solaris modules.
> >>
> >> I tried looking into the system and trying few commands, but thats all
> >> i know about dtrace:
> >>
> >> [root@vcssx247-ldm7 ~]#dtrace -l | grep msg_recv
> >> 7090 fbt mymod msg_recv1 entry
> >> 7091 fbt mymod msg_recv1 return
> >> 7548 fbt mymod msg_recv entry
> >> 7549 fbt mymod msg_recv return
> >>
> >> Any pointers to correct, to the point documentation would be appreciated.
> >>
> >> Thanks
> >> Nayan
> >>
> >
> >
>
>
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