addr2line with FreeBSD kernel failing

[Farhan Khan]

Hi all,

Is there a way to go from a memory address to a kernel symbol?

I am working with a subsystem that uses a lot of function pointers,
and I am not certain which particular function is being called. I have
dtrace(1) printing out the memory address of the function, like this:

printf("Runs vap->iv_newstate: 0x%p", vap->iv_newstate);

The resulting memory address will be 0xffffffff834fa6d0. I was told I
can use addr2line(1), but it seems to fail, as follows:

# addr2line -e /usr/obj/usr/src/amd64.amd64/sys/GENERIC/kernel.full
ffffffff834fa6d0
??:0

Am I doing something wrong? Also, if I can do this directly in
dtrace(1), that would be much much better. This is definitely the
installed kernel, so there is no kernel mismatch. I have also tried
using kernel.debug and kernel, same result.

Thank you,

--
Farhan Khan
PGP Fingerprint: B28D 2726 E2BC A97E 3854 5ABE 9A9F 00BC D525 16EE

[Andriy Gapon]

Post by Farhan Khan
Hi all,
Is there a way to go from a memory address to a kernel symbol?
I am working with a subsystem that uses a lot of function pointers,
and I am not certain which particular function is being called. I have
printf("Runs vap->iv_newstate: 0x%p", vap->iv_newstate);
The resulting memory address will be 0xffffffff834fa6d0. I was told I
# addr2line -e /usr/obj/usr/src/amd64.amd64/sys/GENERIC/kernel.full
ffffffff834fa6d0
??:0

Try 0xffffffff834fa6d0

Post by Farhan Khan
Am I doing something wrong? Also, if I can do this directly in
dtrace(1), that would be much much better. This is definitely the
installed kernel, so there is no kernel mismatch. I have also tried
using kernel.debug and kernel, same result.

[Pratyush Yadav]

Post by Farhan Khan
Hi all,
Is there a way to go from a memory address to a kernel symbol?
I am working with a subsystem that uses a lot of function pointers,
and I am not certain which particular function is being called. I have
printf("Runs vap->iv_newstate: 0x%p", vap->iv_newstate);
The resulting memory address will be 0xffffffff834fa6d0. I was told I
# addr2line -e /usr/obj/usr/src/amd64.amd64/sys/GENERIC/kernel.full
ffffffff834fa6d0
??:0
Am I doing something wrong? Also, if I can do this directly in
dtrace(1), that would be much much better. This is definitely the
installed kernel, so there is no kernel mismatch. I have also tried
using kernel.debug and kernel, same result.

I usually do:

addr2line -e /usr/lib/debug/boot/kernel/kernel.debug <address>

Try that, maybe it will work for you.


PS: I'm not sure addr2line would work for runtime pointers. I use it
to translate the instruction pointer addresses to lines.

--
Regards,
Pratyush Yadav

[Andrew Duane]

addr2line is only for functions, though the manual page could do a more explicit job of saying that....

....................................
Andrew L. Duane - Principal Resident Engineer
AT&T Advanced Services Technical Lead
Juniper Quality Ambassador
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skype: andrewlduane
***@juniper.net

-----Original Message-----
From: owner-freebsd-***@freebsd.org <owner-freebsd-***@freebsd.org> On Behalf Of Pratyush Yadav
Sent: Monday, August 6, 2018 4:33 AM
To: ***@gmail.com
Cc: freebsd-***@freebsd.org
Subject: Re: addr2line with FreeBSD kernel failing

Post by Farhan Khan
Hi all,
Is there a way to go from a memory address to a kernel symbol?
I am working with a subsystem that uses a lot of function pointers,
and I am not certain which particular function is being called. I have
printf("Runs vap->iv_newstate: 0x%p", vap->iv_newstate);
The resulting memory address will be 0xffffffff834fa6d0. I was told I
# addr2line -e /usr/obj/usr/src/amd64.amd64/sys/GENERIC/kernel.full
ffffffff834fa6d0
??:0
Am I doing something wrong? Also, if I can do this directly in
dtrace(1), that would be much much better. This is definitely the
installed kernel, so there is no kernel mismatch. I have also tried
using kernel.debug and kernel, same result.

I usually do:

addr2line -e /usr/lib/debug/boot/kernel/kernel.debug <address>

Try that, maybe it will work for you.


PS: I'm not sure addr2line would work for runtime pointers. I use it to translate the instruction pointer addresses to lines.

--
Regards,
Pratyush Yadav
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[Ryan Stone]

dtrace has native support for decoding symbols with the %a format
specifier. Try this:

printf("Runs vap->iv_newstate: %a", vap->iv_newstate);