On Sun, 8 Jan 2023 at 15:18, Eric Curtin <ecurtin@xxxxxxxxxx> wrote:
>
> On Sun, 8 Jan 2023 at 02:15, Martin Rodriguez Reboredo
> <yakoyoku@xxxxxxxxx> wrote:
> >
> > Version 1.24 of pahole has the capability to exclude compilation units
> > (CUs) of specific languages. Rust, as of writing, is not currently
> > supported by pahole and if it's used with a build that has BTF debugging
> > enabled it results in malformed kernel and module binaries (see
> > Rust-for-Linux/linux#735). So it's better for pahole to exclude Rust
> > CUs until support for it arrives.
> >
> > Reviewed-by: Eric Curtin <ecurtin@xxxxxxxxxx>
> > Tested-by: Eric Curtin <ecurtin@xxxxxxxxxx>
> > Reviewed-by: Neal Gompa <neal@xxxxxxxxx>
> > Tested-by: Neal Gompa <neal@xxxxxxxxx>
> > Signed-off-by: Martin Rodriguez Reboredo <yakoyoku@xxxxxxxxx>
> > ---
> > V1 -> V2: Removed dependency on auto.conf
> >
> > init/Kconfig | 2 +-
> > lib/Kconfig.debug | 9 +++++++++
> > scripts/Makefile.modfinal | 4 ++++
> > scripts/link-vmlinux.sh | 4 ++++
> > 4 files changed, 18 insertions(+), 1 deletion(-)
> >
> > diff --git a/init/Kconfig b/init/Kconfig
> > index 694f7c160c9c..360aef8d7292 100644
> > --- a/init/Kconfig
> > +++ b/init/Kconfig
> > @@ -1913,7 +1913,7 @@ config RUST
> > depends on !MODVERSIONS
> > depends on !GCC_PLUGINS
> > depends on !RANDSTRUCT
> > - depends on !DEBUG_INFO_BTF
> > + depends on !DEBUG_INFO_BTF || PAHOLE_HAS_LANG_EXCLUDE
> > select CONSTRUCTORS
> > help
> > Enables Rust support in the kernel.
> > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> > index ea4c903c9868..d473d491e709 100644
> > --- a/lib/Kconfig.debug
> > +++ b/lib/Kconfig.debug
> > @@ -364,6 +364,15 @@ config PAHOLE_HAS_BTF_TAG
> > btf_decl_tag) or not. Currently only clang compiler implements
> > these attributes, so make the config depend on CC_IS_CLANG.
> >
> > +config PAHOLE_HAS_LANG_EXCLUDE
> > + def_bool PAHOLE_VERSION >= 124
> > + help
> > + Support for the --lang_exclude flag which makes pahole exclude
> > + compilation units from the supplied language. Used in Kbuild to
> > + omit Rust CUs which are not supported in version 1.24 of pahole,
> > + otherwise it would emit malformed kernel and module binaries when
> > + using DEBUG_INFO_BTF_MODULES.
> > +
> > config DEBUG_INFO_BTF_MODULES
> > def_bool y
> > depends on DEBUG_INFO_BTF && MODULES && PAHOLE_HAS_SPLIT_BTF
> > diff --git a/scripts/Makefile.modfinal b/scripts/Makefile.modfinal
> > index 25bedd83644b..a880f2d6918f 100644
> > --- a/scripts/Makefile.modfinal
> > +++ b/scripts/Makefile.modfinal
> > @@ -30,6 +30,10 @@ quiet_cmd_cc_o_c = CC [M] $@
> >
> > ARCH_POSTLINK := $(wildcard $(srctree)/arch/$(SRCARCH)/Makefile.postlink)
> >
> > +ifdef CONFIG_RUST
> > +PAHOLE_FLAGS += --lang_exclude=rust
> > +endif
> > +
> > quiet_cmd_ld_ko_o = LD [M] $@
> > cmd_ld_ko_o += \
> > $(LD) -r $(KBUILD_LDFLAGS) \
> > diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
> > index 918470d768e9..69eb0bea89bf 100755
> > --- a/scripts/link-vmlinux.sh
> > +++ b/scripts/link-vmlinux.sh
> > @@ -122,6 +122,10 @@ gen_btf()
> > return 1
> > fi
> >
> > + if is_enabled CONFIG_RUST; then
> > + PAHOLE_FLAGS="${PAHOLE_FLAGS} --lang_exclude=rust"
> > + fi
>
> If it was me, I would do things more like v1 of the patch (instead
> just checking pahole version), because this is the only flag set in
> scripts/Makefile.modfinal, which is a little confusing and
> inconsistent. It's ok to set --lang_exclude=rust in all cases, as long
> as pahole_ver is recent enough.
>
> +if [ "${pahole_ver}" -ge "124" ]; then
> + # see PAHOLE_HAS_LANG_EXCLUDE
> + extra_paholeopt="${extra_paholeopt} --lang_exclude=rust"
> +fi
>
> But I'm not too opinionated either on this so...
>
> Reviewed-by: Eric Curtin <ecurtin@xxxxxxxxxx>
>
> can be reapplied. I'm gonna test this again to see if it works in a
> Fedora Asahi rpm build.
After testing I probably have to retract my Reviewed-by tag,
apologies, bpf and all that did not work with this patch when I built
in the fedora way, but, the good news is when I alter v1 of the patch
to just check pahole version like so (instead of the is_enabled
check):
+if [ "${pahole_ver}" -ge "124" ]; then
+ # see PAHOLE_HAS_LANG_EXCLUDE
+ extra_paholeopt="${extra_paholeopt} --lang_exclude=rust"
+fi
it worked just fine, and that should satisfy the testbot and all the
other ways we build too. Could we change to that @Martin Rodriguez
Reboredo ?
>
>
> > +
> > vmlinux_link ${1}
> >
> > info "BTF" ${2}
> > --
> > 2.39.0
> >
