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Re: How to debug what I am doing wrong?


> So eu-unstrip doesn't have a man page, so I'm not 100% sure what this
> is doing, but:

Yeah, sorry about that.  I'm sometimes decent at consing new frobs, but
always lousy at documenting.  It does have --help, though it is rather
nonobvious til you read it all that -n makes it do something entirely
different. ;-)

 With -n no files are written, but one line to standard output for each module:
	 START+SIZE BUILDID FILE DEBUGFILE MODULENAME
 START and SIZE are hexadecimal giving the address bounds of the module.
 BUILDID is hexadecimal for the build ID bits, or - if no ID is known; the
 hexadecimal may be followed by @0xADDR giving the address where the ID resides
 if that is known.  FILE is the file name found for the module, or - if none was
 found, or . if an ELF image is available but not from any named file.
 DEBUGFILE is the separate debuginfo file name, or - if no debuginfo was found,
 or . if FILE contains the debug information.

> 140%  eu-unstrip -n -K ext4dev
> 0x9aa300+0x2f588 a8976215a438326936201ee03829fa3230fed123@0x9aa324 /lib/modules/2.6.26-03033-g97438cf/kernel/fs/ext4/ext4dev.ko - ext4dev

So, this says it found the module (file name) but found no debug file (-),
same as systemtap.

> 141% eu-unstrip -n -e /lib/modules/2.6.26-03033-g97438cf/kernel/fs/ext4/ext4dev.ko
> 0+0x2f588 a8976215a438326936201ee03829fa3230fed123@0x24 /lib/modules/2.6.26-03033-g97438cf/kernel/fs/ext4/ext4dev.ko - 

This says the same about just looking at the file by name (as a generic
ET_REL file, the tool not caring that it's a .ko) and trying to find its
debug file.

> 142% eu-unstrip -n -e /usr/lib/debug/lib/modules/2.6.26-03033-g97438cf/kernel/fs/ext4/ext4dev.ko
> 0+0x2f588 a8976215a438326936201ee03829fa3230fed123@0x24 /usr/lib/debug/lib/modules/2.6.26-03033-g97438cf/kernel/fs/ext4/ext4dev.ko . 

This says that the file you pointed it to explicitly does itself contain
satisfactory DWARF sections (.).

> Does this tell you anything useful?

It does.  It now seems likely the bug is in the libdwfl code for searching
for debuginfo files and/or its code for validating them.  (In this case, it
should be validating that the build ID matches.)

If you send me both of those files (a tar with each by its full dir name
would be handy), I should be able to reproduce this and fix the bug.


Thanks,
Roland


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