[Bug debugedit/27636] New: Debugedit doesn't handle compressed debug ELF sections

[Bug debugedit/27636] New: Debugedit doesn't handle compressed debug ELF sections

[mark at klomp dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=27636

            Bug ID: 27636
           Summary: Debugedit doesn't handle compressed debug ELF sections
           Product: debugedit
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: debugedit
          Assignee: unassigned at sourceware dot org
          Reporter: mark at klomp dot org
                CC: debugedit at sourceware dot org
  Target Milestone: ---

When seeing compressed debug ELF sections debugedit gets confused:

debugedit: ./foo.o: DWARF version 0 unhandled

This is a somewhat useless error message.

We should at least detect SHF_COMPRESSED (or .zdebug...) and explicitly say we
don't handle compressed sections.

If we do decide to handle compressed sections there are a couple of ways:
- Do we simply always uncompress and leave it that way?
- Do we recompress afterwards?
- Do we require an explicit flag to (de/re)compress?

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[Bug debugedit/27636] Debugedit doesn't handle compressed debug ELF sections

[mark at klomp dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=27636

--- Comment #1 from Mark Wielaard <mark at klomp dot org> ---
https://sourceware.org/pipermail/debugedit/2022-November/000160.html

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[Bug debugedit/27636] Debugedit doesn't handle compressed debug ELF sections

[mark at klomp dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=27636

Mark Wielaard <mark at klomp dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
             Status|NEW                         |RESOLVED

--- Comment #2 from Mark Wielaard <mark at klomp dot org> ---
commit 3e7aeeab4f744ad15108775685db68d3a35b0735
Author: Mark Wielaard <mark@klomp.org>
Date:   Thu Mar 23 18:07:40 2023 +0100

    debugedit: Add support for .debug_str_offsets (DW_FORM_strx)

    In theory supporting strx .debug_str_offsets is easy, the strings in
    .debug_str are just read through an indirection table. When the
    strings are updated in .debug_str we just need to rewrite the
    indirection table.

    The tricky part is the ET_REL (object files or kernel modules)
    support. Relocation reading is "global" per section and we expect to
    read a relocation only once. But we need to read the
    DW_AT_str_offsets_base before reading any strx form attributes. So we
    read that first, then reset the relptr. And when we read from the
    .debug_str_offsets section we need to save and restore the .debug_info
    relptr.

            * tools/debugedit.c (do_read_24): New function.
            (str_offsets_base): New static variable.
            (buf_read_ule24): New function.
            (buf_read_ube24): Likewise.
            (setup_relbuf): Handle .debug_str_offsets.
            (do_read_uleb128): New function.
            (do_read_str_form_relocated): Likewise.
            (read_abbrev): Handle DW_FORM_strx[1234].
            (edit_strp): Take the actual string form as argument.
            Use do_read_str_form_relocated.
            (read_dwarf5_line_entries): Pass form to edit_strp.
            (edit_attributes_str_comp_dir): Take the actual string
            form as argument. Use do_read_str_form_relocated.
            (edit_attributes): Handle DW_FORM_strx[1234].
            (edit_info): Read DW_AT_str_offsets_base first.
            (update_str_offsets): New function.
            (edit_dwarf2): Setup do_read_24. Call update_str_offsets.

    https://sourceware.org/bugzilla/show_bug.cgi?id=28728

    Signed-off-by: Mark Wielaard <mark@klomp.org>

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[Bug debugedit/27636] Debugedit doesn't handle compressed debug ELF sections

[mark at klomp dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=27636

Mark Wielaard <mark at klomp dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
         Resolution|FIXED                       |---

--- Comment #3 from Mark Wielaard <mark at klomp dot org> ---
Sorry, wrong bug. sigh.

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[Bug debugedit/27636] Debugedit doesn't handle compressed debug ELF sections

[hjl.tools at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=27636

H.J. Lu <hjl.tools at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|REOPENED                    |NEW

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[Bug debugedit/27636] Debugedit doesn't handle compressed debug ELF sections

[mark at klomp dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=27636

Mark Wielaard <mark at klomp dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           See Also|                            |https://sourceware.org/bugz
                   |                            |illa/show_bug.cgi?id=32102

--- Comment #4 from Mark Wielaard <mark at klomp dot org> ---
(In reply to Mark Wielaard from comment #0)
> If we do decide to handle compressed sections there are a couple of ways:
> - Do we simply always uncompress and leave it that way?
> - Do we recompress afterwards?

Adding this to the patch suggested in comment #1 ran into this elfutils bug:
https://sourceware.org/bugzilla/show_bug.cgi?id=32102

So for now the easiest way is to just uncompress and leave it like that.

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