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RE: interesting option of stap


Thanks for you help,

With -vvv, I get:

dump_unwindsyms kernel index=0 base=0x0
Found build-id in kernel, length 20, start at 0x10 -> so build_id_vaddr = 0x10
Found kernel _stext extra offset 0xc0008000 -> extra_offset=0xC0008000. Effectively, 0xc0008000 is the _stext section address I can see in my System.map

As modname is kernel, we execute:
c->output << ".build_id_offset = 0x" << hex << build_id_vaddr - (base + extra_offset)

i.e. 0x10 - (0x0 + 0xC0008000) = 0xFFFFFFFF 3FFF8010, which is what I get in stap-symbols.h


With --stfu-kbuild-i-know-better, the generated .ko with the warning seemed to work OK. So the patch from William would probably work. But I am not following everything about this 64bits elf address and this build_id_offset that is a long.
By the way, my elf-utils lib is .143, which seems recent enough.

And I don't see which binary "module 0" refers to. Where shall I find it ?

Regards
Fred

Frederic Turgis
OMAP Platform Business Unit - OMAP System Engineering - Platform Enablement



Texas Instruments France SA, 821 Avenue Jack Kilby, 06270 Villeneuve Loubet. 036 420 040 R.C.S Antibes. Capital de EUR 753.920

-----Original Message-----

From: Roland McGrath [mailto:roland@redhat.com]
Sent: Monday, February 21, 2011 8:23 PM
To: William Cohen
Cc: Turgis, Frederic; systemtap@sourceware.org
Subject: Re: interesting option of stap

It looks like a bug in the relocatability code to me.  That looks like a negative offset coming out, and it should never be negative.  Perhaps Frederic can make available the ARM binary that "module 0" refers to, so we can investigate the analysis stap is doing it.

Thanks,
Roland


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