objdump -S for a different dir.

[Jim Cromie]

hi folks,

out of habit, I build my kernels to a build tree
ie use make O=../build-foo just once,
then cd ../build-foo, and thereafter run make there

this doesnt play nice with objdump -S
--source
           Display source code intermixed with disassembly, if
possible.  Implies -d.

it seems its not possible unless the source and obj are in the same file.
GDB manages to find the source, whats missing in objdump ?

FWIW, Id love a micro-tutorial on this,
anyone know how to display, dissect the obj file, debuginfo etc ?
or can recommend some on-line tome that gets into it at some breadth and depth ?
many many search hits are for quick Q&A that doesnt get deeper than a puddle.

thanks