mirror of
https://github.com/torvalds/linux.git
synced 2024-12-15 07:33:56 +00:00
c25e1c5582
When CONFIG_LTO_CLANG=y, additional intermediate *.prelink.o is created
for each module. Also, objtool is postponed until LLVM IR is converted
to ELF.
CONFIG_X86_KERNEL_IBT works in a similar way to postpone objtool until
objects are merged together.
This commit stops generating *.prelink.o, so the build flow will look
similar with/without LTO.
The following figures show how the LTO build currently works, and
how this commit is changing it.
Current build flow
==================
[1] single-object module
$(LD)
$(CC) +objtool $(LD)
foo.c --------------------> foo.o -----> foo.prelink.o -----> foo.ko
(LLVM IR) (ELF) | (ELF)
|
foo.mod.o --/
(LLVM IR)
[2] multi-object module
$(LD)
$(CC) $(AR) +objtool $(LD)
foo1.c -----> foo1.o -----> foo.o -----> foo.prelink.o -----> foo.ko
| (archive) (ELF) | (ELF)
foo2.c -----> foo2.o --/ |
(LLVM IR) foo.mod.o --/
(LLVM IR)
One confusion is that foo.o in multi-object module is an archive
despite of its suffix.
New build flow
==============
[1] single-object module
Since there is only one object, there is no need to keep the LLVM IR.
Use $(CC)+$(LD) to generate an ELF object in one build rule. When LTO
is disabled, $(LD) is unneeded because $(CC) produces an ELF object.
$(CC)+$(LD)+objtool $(LD)
foo.c ----------------------------> foo.o ---------> foo.ko
(ELF) | (ELF)
|
foo.mod.o --/
(LLVM IR)
[2] multi-object module
Previously, $(AR) was used to combine LLVM IR files into an archive,
but there was no technical reason to do so. Use $(LD) to merge them
into a single ELF object.
$(LD)
$(CC) +objtool $(LD)
foo1.c ---------> foo1.o ---------> foo.o ---------> foo.ko
| (ELF) | (ELF)
foo2.c ---------> foo2.o ----/ |
(LLVM IR) foo.mod.o --/
(LLVM IR)
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # LLVM-14 (x86-64)
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
147 lines
4.2 KiB
Makefile
147 lines
4.2 KiB
Makefile
# SPDX-License-Identifier: GPL-2.0
|
|
# ===========================================================================
|
|
# Module versions
|
|
# ===========================================================================
|
|
#
|
|
# Stage one of module building created the following:
|
|
# a) The individual .o files used for the module
|
|
# b) A <module>.o file which is the .o files above linked together
|
|
# c) A <module>.mod file, listing the name of the preliminary <module>.o file,
|
|
# plus all .o files
|
|
# d) modules.order, which lists all the modules
|
|
|
|
# Stage 2 is handled by this file and does the following
|
|
# 1) Find all modules listed in modules.order
|
|
# 2) modpost is then used to
|
|
# 3) create one <module>.mod.c file per module
|
|
# 4) create one Module.symvers file with CRC for all exported symbols
|
|
|
|
# Step 3 is used to place certain information in the module's ELF
|
|
# section, including information such as:
|
|
# Version magic (see include/linux/vermagic.h for full details)
|
|
# - Kernel release
|
|
# - SMP is CONFIG_SMP
|
|
# - PREEMPT is CONFIG_PREEMPT[_RT]
|
|
# - GCC Version
|
|
# Module info
|
|
# - Module version (MODULE_VERSION)
|
|
# - Module alias'es (MODULE_ALIAS)
|
|
# - Module license (MODULE_LICENSE)
|
|
# - See include/linux/module.h for more details
|
|
|
|
# Step 4 is solely used to allow module versioning in external modules,
|
|
# where the CRC of each module is retrieved from the Module.symvers file.
|
|
|
|
# KBUILD_MODPOST_NOFINAL can be set to skip the final link of modules.
|
|
# This is solely useful to speed up test compiles
|
|
|
|
PHONY := __modpost
|
|
__modpost:
|
|
|
|
include include/config/auto.conf
|
|
include $(srctree)/scripts/Kbuild.include
|
|
|
|
MODPOST = scripts/mod/modpost \
|
|
$(if $(CONFIG_MODVERSIONS),-m) \
|
|
$(if $(CONFIG_MODULE_SRCVERSION_ALL),-a) \
|
|
$(if $(CONFIG_SECTION_MISMATCH_WARN_ONLY),,-E) \
|
|
-o $@
|
|
|
|
ifdef MODPOST_VMLINUX
|
|
|
|
quiet_cmd_modpost = MODPOST $@
|
|
cmd_modpost = $(MODPOST) $<
|
|
|
|
vmlinux.symvers: vmlinux.o
|
|
$(call cmd,modpost)
|
|
|
|
__modpost: vmlinux.symvers
|
|
|
|
else
|
|
|
|
ifeq ($(KBUILD_EXTMOD),)
|
|
|
|
input-symdump := vmlinux.symvers
|
|
output-symdump := modules-only.symvers
|
|
|
|
quiet_cmd_cat = GEN $@
|
|
cmd_cat = cat $(real-prereqs) > $@
|
|
|
|
ifneq ($(wildcard vmlinux.symvers),)
|
|
|
|
__modpost: Module.symvers
|
|
Module.symvers: vmlinux.symvers modules-only.symvers FORCE
|
|
$(call if_changed,cat)
|
|
|
|
targets += Module.symvers
|
|
|
|
endif
|
|
|
|
else
|
|
|
|
# set src + obj - they may be used in the modules's Makefile
|
|
obj := $(KBUILD_EXTMOD)
|
|
src := $(obj)
|
|
|
|
# Include the module's Makefile to find KBUILD_EXTRA_SYMBOLS
|
|
include $(or $(wildcard $(src)/Kbuild), $(src)/Makefile)
|
|
|
|
# modpost option for external modules
|
|
MODPOST += -e
|
|
|
|
input-symdump := Module.symvers $(KBUILD_EXTRA_SYMBOLS)
|
|
output-symdump := $(KBUILD_EXTMOD)/Module.symvers
|
|
|
|
endif
|
|
|
|
existing-input-symdump := $(wildcard $(input-symdump))
|
|
|
|
# modpost options for modules (both in-kernel and external)
|
|
MODPOST += \
|
|
$(addprefix -i ,$(existing-input-symdump)) \
|
|
$(if $(KBUILD_NSDEPS),-d $(MODULES_NSDEPS)) \
|
|
$(if $(CONFIG_MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS)$(KBUILD_NSDEPS),-N)
|
|
|
|
# 'make -i -k' ignores compile errors, and builds as many modules as possible.
|
|
ifneq ($(findstring i,$(filter-out --%,$(MAKEFLAGS))),)
|
|
MODPOST += -n
|
|
endif
|
|
|
|
# Clear VPATH to not search for *.symvers in $(srctree). Check only $(objtree).
|
|
VPATH :=
|
|
$(input-symdump):
|
|
@echo >&2 'WARNING: Symbol version dump "$@" is missing.'
|
|
@echo >&2 ' Modules may not have dependencies or modversions.'
|
|
@echo >&2 ' You may get many unresolved symbol warnings.'
|
|
|
|
# KBUILD_MODPOST_WARN can be set to avoid error out in case of undefined symbols
|
|
ifneq ($(KBUILD_MODPOST_WARN)$(filter-out $(existing-input-symdump), $(input-symdump)),)
|
|
MODPOST += -w
|
|
endif
|
|
|
|
# Read out modules.order to pass in modpost.
|
|
# Otherwise, allmodconfig would fail with "Argument list too long".
|
|
quiet_cmd_modpost = MODPOST $@
|
|
cmd_modpost = sed 's/ko$$/o/' $< | $(MODPOST) -T -
|
|
|
|
$(output-symdump): $(MODORDER) $(input-symdump) FORCE
|
|
$(call if_changed,modpost)
|
|
|
|
targets += $(output-symdump)
|
|
|
|
__modpost: $(output-symdump)
|
|
ifneq ($(KBUILD_MODPOST_NOFINAL),1)
|
|
$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modfinal
|
|
endif
|
|
|
|
PHONY += FORCE
|
|
FORCE:
|
|
|
|
existing-targets := $(wildcard $(sort $(targets)))
|
|
|
|
-include $(foreach f,$(existing-targets),$(dir $(f)).$(notdir $(f)).cmd)
|
|
|
|
endif
|
|
|
|
.PHONY: $(PHONY)
|