On Tue, Feb 03, 2026 at 01:55:05PM +0100, Thomas Weißschuh wrote: > On 2026-01-30 18:06:20+0100, Petr Pavlu wrote: > > On 1/13/26 1:28 PM, Thomas Weißschuh wrote: > > > Normally the .ko module files depend on a fully built vmlinux to be > > > available for modpost validation and BTF generation. With > > > CONFIG_MODULE_HASHES, vmlinux now depends on the modules > > > to build a merkle tree. This introduces a dependency cycle which is > > > impossible to satisfy. Work around this by building the modules during > > > link-vmlinux.sh, after vmlinux is complete enough for modpost and BTF > > > but before the final module hashes are > > > > I wonder if this dependency cycle could be resolved by utilizing the > > split into vmlinux.unstripped and vmlinux that occurred last year. > > > > The idea is to create the following ordering: vmlinux.unstripped -> > > modules -> vmlinux, and to patch in .module_hashes only when building > > the final vmlinux. > > > > This would require the following: > > * Split scripts/Makefile.vmlinux into two Makefiles, one that builds the > > current vmlinux.unstripped and the second one that builds the final > > vmlinux from it. > > * Modify the top Makefile to recognize vmlinux.unstripped and update the > > BTF generation rule 'modules: vmlinux' to > > 'modules: vmlinux.unstripped'. > > * Add the 'vmlinux: modules' ordering in the top Makefile for > > CONFIG_MODULE_HASHES=y. > > * Remove the patching of vmlinux.unstripped in scripts/link-vmlinux.sh > > and instead move it into scripts/Makefile.vmlinux when running objcopy > > to produce the final vmlinux. > > > > I think this approach has two main advantages: > > * CONFIG_MODULE_HASHES can be made orthogonal to > > CONFIG_DEBUG_INFO_BTF_MODULES. > > * All dependencies are expressed at the Makefile level instead of having > > scripts/link-vmlinux.sh invoke 'make -f Makefile modules'. > > > > Below is a rough prototype that applies on top of this series. It is a > > bit verbose due to the splitting of part of scripts/Makefile.vmlinux > > into scripts/Makefile.vmlinux_unstripped. > > That looks like a feasible alternative. Before adopting it, I'd like to > hear the preference of the kbuild folks.
After the first run-through, the proposed alternative sounds good. Unfortunately, I ran out of time for this week. I can give a more founded reply in a few days. Kind regards, Nicolas > > diff --git a/Makefile b/Makefile > > index 841772a5a260..19a3beb82fa7 100644 > > --- a/Makefile > > +++ b/Makefile > > @@ -1259,7 +1259,7 @@ vmlinux_o: vmlinux.a $(KBUILD_VMLINUX_LIBS) > > vmlinux.o modules.builtin.modinfo modules.builtin: vmlinux_o > > @: > > > > -PHONY += vmlinux > > +PHONY += vmlinux.unstripped vmlinux > > # LDFLAGS_vmlinux in the top Makefile defines linker flags for the top > > vmlinux, > > # not for decompressors. LDFLAGS_vmlinux in > > arch/*/boot/compressed/Makefile is > > # unrelated; the decompressors just happen to have the same base name, > > @@ -1270,9 +1270,11 @@ PHONY += vmlinux > > # https://savannah.gnu.org/bugs/?61463 > > # For Make > 4.4, the following simple code will work: > > # vmlinux: private export LDFLAGS_vmlinux := $(LDFLAGS_vmlinux) > > -vmlinux: private _LDFLAGS_vmlinux := $(LDFLAGS_vmlinux) > > -vmlinux: export LDFLAGS_vmlinux = $(_LDFLAGS_vmlinux) > > -vmlinux: vmlinux.o $(KBUILD_LDS) modpost > > +vmlinux.unstripped: private _LDFLAGS_vmlinux := $(LDFLAGS_vmlinux) > > +vmlinux.unstripped: export LDFLAGS_vmlinux = $(_LDFLAGS_vmlinux) > > +vmlinux.unstripped: vmlinux.o $(KBUILD_LDS) modpost > > + $(Q)$(MAKE) -f $(srctree)/scripts/Makefile.vmlinux_unstripped > > +vmlinux: vmlinux.unstripped > > $(Q)$(MAKE) -f $(srctree)/scripts/Makefile.vmlinux > > Maybe we could keep them together in a single Makefile, > and instead have different targets in it. > > (...) > > > @@ -98,70 +44,15 @@ remove-symbols := -w > > --strip-unneeded-symbol='__mod_device_table__*' > > # To avoid warnings: "empty loadable segment detected at ..." from GNU > > objcopy, > > # it is necessary to remove the PT_LOAD flag from the segment. > > quiet_cmd_strip_relocs = OBJCOPY $@ > > - cmd_strip_relocs = $(OBJCOPY) $(patsubst %,--set-section-flags > > %=noload,$(remove-section-y)) $< $@; \ > > - $(OBJCOPY) $(addprefix > > --remove-section=,$(remove-section-y)) $(remove-symbols) $@ > > + cmd_script_relocs = $(OBJCOPY) $(patsubst %,--set-section-flags > > %=noload,$(remove-section-y)) $< $@; \ > > + $(OBJCOPY) $(addprefix > > --remove-section=,$(remove-section-y)) \ > > + $(remove-symbols) \ > > + $(patch-module-hashes) $@ > > cmd_script_relocs -> cmd_strip_relocs > > (...) -- Nicolas
