Bug 28728 - Unknown DWARF DW_FORM_0x25 (DW_FORM_strx)
Summary: Unknown DWARF DW_FORM_0x25 (DW_FORM_strx)
Status: NEW
Alias: None
Product: debugedit
Classification: Unclassified
Component: debugedit (show other bugs)
Version: unspecified
: P2 normal
Target Milestone: ---
Assignee: Not yet assigned to anyone
URL:
Keywords:
: 29773 (view as bug list)
Depends on:
Blocks:
 
Reported: 2021-12-27 07:23 UTC by Vitaly Chikunov
Modified: 2023-09-24 18:10 UTC (History)
9 users (show)

See Also:
Host:
Target:
Build:
Last reconfirmed: 2021-12-27 00:00:00

Attachments
Example of compiled module (319.81 KB, application/x-object)
2021-12-27 07:23 UTC, Vitaly Chikunov 		Details
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Description Vitaly Chikunov 2021-12-27 07:23:56 UTC 
Created attachment 13884 [details]
Example of compiled module

When building Linux kernel with[1] CC=clang LLVM=1 and CONFIG_DEBUG_INFO_DWARF5=y debugedit reports error when processing compiled kernel modules, such as

  debugedit: ./lib/modules/5.16.0+rc6.20211223-drm-tip-alt1/kernel/sound/usb/caiaq/snd-usb-caiaq.ko: Unknown DWARF DW_FORM_0x25

[1] https://www.kernel.org/doc/html/latest/kbuild/llvm.html
Comment 1 Vitaly Chikunov 2021-12-27 07:30:24 UTC 
Also, it seems, debugedit is unable to extract source list from such binary.
Comment 2 Mark Wielaard 2021-12-27 10:40:42 UTC 
(In reply to Vitaly Chikunov from comment #0)
> When building Linux kernel with[1] CC=clang LLVM=1 and
> CONFIG_DEBUG_INFO_DWARF5=y debugedit reports error when processing compiled
> kernel modules, such as
> 
>   debugedit:
> ./lib/modules/5.16.0+rc6.20211223-drm-tip-alt1/kernel/sound/usb/caiaq/snd-
> usb-caiaq.ko: Unknown DWARF DW_FORM_0x25

That is DW_FORM_strx1, which is only partially supported by debugedit. Normally the DW_FORM_strx forms are only used when generating split DWARF (.dwo) files. Best workaround for now is to not use DWARF5 with llvm (which isn't the default for clang/llvm anyway).
Comment 3 James Beddek 2022-02-18 07:41:05 UTC 
(In reply to Mark Wielaard from comment #2)
> (In reply to Vitaly Chikunov from comment #0)
> > When building Linux kernel with[1] CC=clang LLVM=1 and
> > CONFIG_DEBUG_INFO_DWARF5=y debugedit reports error when processing compiled
> > kernel modules, such as
> > 
> >   debugedit:
> > ./lib/modules/5.16.0+rc6.20211223-drm-tip-alt1/kernel/sound/usb/caiaq/snd-
> > usb-caiaq.ko: Unknown DWARF DW_FORM_0x25
> 
> That is DW_FORM_strx1, which is only partially supported by debugedit.
> Normally the DW_FORM_strx forms are only used when generating split DWARF
> (.dwo) files. Best workaround for now is to not use DWARF5 with llvm (which
> isn't the default for clang/llvm anyway).

DWARFv5 is now the default with the upcoming Clang 14.0.0 release: https://github.com/llvm/llvm-project/blob/e80c52986e1bb3afa6a92c58b1cb897877923a66/clang/docs/ReleaseNotes.rst#dwarf-support-in-clang

At the moment debugedit warns for almost any binary compiled with Clang 14.0.0-rc1
Comment 4 James Beddek 2022-02-18 07:47:25 UTC 
Additionally from what I can tell the flags to re-enable DWARFv4, -gdwarf-4, and -fdebug-default-version=4 do nothing to silence this issue.
Comment 5 Sam James 2022-11-09 06:58:38 UTC 
(In reply to James Beddek from comment #4)
> Additionally from what I can tell the flags to re-enable DWARFv4, -gdwarf-4,
> and -fdebug-default-version=4 do nothing to silence this issue.

CC=clang CFLAGS="-gdwarf-4 -fdebug-default-version=4" ... doesn't give a warning for me at least. This has been bugging me for a while, glad I found it.
Comment 6 Sam James 2022-11-11 05:06:07 UTC 
*** Bug 29773 has been marked as a duplicate of this bug. ***
Comment 7 Seppo Yli-Olli 2023-09-24 18:10:54 UTC 
This is now reproducing basically everywhere where LLVM17 clang is used. The workaround to use DWARF4 seems quite unexpected now that DWARF5 is these days the norm for everything.