Re: Porting pahole from dwarf_next_unit() to dwarf_get_units()

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



Em Tue, Dec 05, 2023 at 01:03:01PM +0000, Dimitri John Ledkov escreveu:
> Currently pahole warns and does nothing upon hitting
> DW_TAG_skeleton_unit as implemented at
> https://git.kernel.org/pub/scm/devel/pahole/pahole.git/commit/?id=0135ccd632796ab3aff65b7c99b374c4682c2bcf
> 
> In elfutils, a while back a new API got added that aids with discovery
> and processing of such tags -
> https://sourceware.org/git/?p=elfutils.git;a=commitdiff;h=79f0e623dcde4b042bb72f636a2211d67d5c0ade
> 
> It seems to me if pahole is ported from using dwarf_next_unit() to
> instead use dwarf_get_units() native support can be added for
> split-dwarf (dwo) files.

That would be awesome!
 
> I am trying to write such a port, but it is proving to be very
> difficult.

I did some work on supporting split-dwarf months ago, but got
sidetracked with other work, BTF related and then the code bitrotted, I
have to go back looking at it to swap back the details into my brain:

https://git.kernel.org/pub/scm/devel/pahole/pahole.git/log/?h=alt_dwarf

The patches after:

45c044860c2abce7 dwarf_loader: Sync with LINUX_ELFNOTE_LTO_INFO macro from kernel

Are the ones to suport alt dwarf.

> I am entirely unfamiliar with neither pahole nor libdw nor
> the dwarf file format. Thus it is very confusing when both pahole and
> dwarf library use very similar type names and structs. For example
> libdw has struct Dwarf_CU and pahole has unrelated dwarf_cu struct.
 
> What are the differences between dwarf_nextcu(), dwarf_next_unit(),
> dwarf_get_units() and when should one use each one of them? (or nest
> them?)

> Is a port of https://git.kernel.org/pub/scm/devel/pahole/pahole.git/tree/dwarf_loader.c?id=0135ccd632796ab3aff65b7c99b374c4682c2bcf
> to use dwarf_get_units() a right approach and would be welcomed?

Yes, we need to support DWARF5 fully.
 
> Is anyone else interested in providing any help, or guidance?

I'm interested, and I think if Mark could help it would be great as
well.

- ARnaldo




[Index of Archives]     [Linux USB Devel]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]

  Powered by Linux