linux-kernel - Re: [PATCH v2] kbuild: Require pahole <v1.28 or >v1.29 with GENDWARFKSYMS on X86

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <CAK7LNARSsMF2E57fTNk6jYfb3OocB1RYgZKShfPoEDYdU_fQoA@mail.gmail.com>
Date: Tue, 6 May 2025 16:03:59 +0900
From: Masahiro Yamada <masahiroy@...nel.org>
To: Sami Tolvanen <samitolvanen@...gle.com>
Cc: Luis Chamberlain <mcgrof@...nel.org>, Petr Pavlu <petr.pavlu@...e.com>, 
	Daniel Gomez <da.gomez@...sung.com>, linux-modules@...r.kernel.org, 
	linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Paolo Pisati <paolo.pisati@...onical.com>
Subject: Re: [PATCH v2] kbuild: Require pahole <v1.28 or >v1.29 with
 GENDWARFKSYMS on X86

On Tue, Apr 8, 2025 at 8:08 AM Sami Tolvanen <samitolvanen@...gle.com> wrote:
>
> With CONFIG_GENDWARFKSYMS, __gendwarfksyms_ptr variables are
> added to the kernel in EXPORT_SYMBOL() to ensure DWARF type
> information is available for exported symbols in the TUs where
> they're actually exported. These symbols are dropped when linking
> vmlinux, but dangling references to them remain in DWARF.
>
> With CONFIG_DEBUG_INFO_BTF enabled on X86, pahole versions after
> commit 47dcb534e253 ("btf_encoder: Stop indexing symbols for
> VARs") and before commit 9810758003ce ("btf_encoder: Verify 0
> address DWARF variables are in ELF section") place these symbols
> in the .data..percpu section, which results in an "Invalid
> offset" error in btf_datasec_check_meta() during boot, as all
> the variables are at zero offset and have non-zero size. If
> CONFIG_DEBUG_INFO_BTF_MODULES is enabled, this also results in a
> failure to load modules with:
>
>   failed to validate module [$module] BTF: -22
>
> As the issue occurs in pahole v1.28 and the fix was merged
> after v1.29 was released, require pahole <v1.28 or >v1.29 when
> GENDWARFKSYMS is enabled with DEBUG_INFO_BTF on X86.
>
> Reported-by: Paolo Pisati <paolo.pisati@...onical.com>
> Signed-off-by: Sami Tolvanen <samitolvanen@...gle.com>
> ---
>

Applied to linux-kbuild.

Thanks.



> Changes in v2:
> - Also allow pahole <v1.28.
> - Update comment to include the affected commit range.
>
> ---
>  kernel/module/Kconfig | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/kernel/module/Kconfig b/kernel/module/Kconfig
> index d7762ef5949a..39278737bb68 100644
> --- a/kernel/module/Kconfig
> +++ b/kernel/module/Kconfig
> @@ -192,6 +192,11 @@ config GENDWARFKSYMS
>         depends on !DEBUG_INFO_REDUCED && !DEBUG_INFO_SPLIT
>         # Requires ELF object files.
>         depends on !LTO
> +       # To avoid conflicts with the discarded __gendwarfksyms_ptr symbols on
> +       # X86, requires pahole before commit 47dcb534e253 ("btf_encoder: Stop
> +       # indexing symbols for VARs") or after commit 9810758003ce ("btf_encoder:
> +       # Verify 0 address DWARF variables are in ELF section").
> +       depends on !X86 || !DEBUG_INFO_BTF || PAHOLE_VERSION < 128 || PAHOLE_VERSION > 129
>         help
>           Calculate symbol versions from DWARF debugging information using
>           gendwarfksyms. Requires DEBUG_INFO to be enabled.
>
> base-commit: 0af2f6be1b4281385b618cb86ad946eded089ac8
> --
> 2.49.0.504.g3bcea36a83-goog
>


-- 
Best Regards
Masahiro Yamada