kbuild: Fixup the IBT kbuild changes

Masahiro-san deemed my kbuild changes to support whole module objtool
runs too terrible to live and gracefully provided an alternative.

Suggested-by: Masahiro Yamada <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Link: https://lkml.kernel.org/r/CAK7LNAQ2mYMnOKMQheVi+6byUFE3KEkjm1zcndNUfe0tORGvug@mail.gmail.com

Author: Peter Zijlstra

scripts/Makefile.build

@@ -86,18 +86,12 @@ ifdef need-builtin
 targets-for-builtin += $(obj)/built-in.a
 endif
 
-targets-for-modules :=
+targets-for-modules := $(patsubst %.o, %.mod, $(filter %.o, $(obj-m)))
 
-ifdef CONFIG_LTO_CLANG
-targets-for-modules += $(patsubst %.o, %.lto.o, $(filter %.o, $(obj-m)))
-endif
-
-ifdef CONFIG_X86_KERNEL_IBT
-targets-for-modules += $(patsubst %.o, %.objtool, $(filter %.o, $(obj-m)))
+ifneq ($(CONFIG_LTO_CLANG)$(CONFIG_X86_KERNEL_IBT),)
+targets-for-modules += $(patsubst %.o, %.prelink.o, $(filter %.o, $(obj-m)))
 endif
 
-targets-for-modules += $(patsubst %.o, %.mod, $(filter %.o, $(obj-m)))
-
 ifdef need-modorder
 targets-for-modules += $(obj)/modules.order
 endif
@@ -244,31 +238,16 @@ objtool_args =								\
 	$(if $(CONFIG_FTRACE_MCOUNT_USE_OBJTOOL), --mcount)		\
 	$(if $(CONFIG_SLS), --sls)
 
-cmd_objtool = $(if $(objtool-enabled), ; $(objtool) $(objtool_args) $(@:.objtool=.o))
-cmd_gen_objtooldep = $(if $(objtool-enabled), { echo ; echo '$(@:.objtool=.o): $$(wildcard $(objtool))' ; } >> $(dot-target).cmd)
+cmd_objtool = $(if $(objtool-enabled), ; $(objtool) $(objtool_args) $@)
+cmd_gen_objtooldep = $(if $(objtool-enabled), { echo ; echo '$@: $$(wildcard $(objtool))' ; } >> $(dot-target).cmd)
 
 endif # CONFIG_STACK_VALIDATION
 
-ifdef CONFIG_LTO_CLANG
+ifneq ($(CONFIG_LTO_CLANG)$(CONFIG_X86_KERNEL_IBT),)
 
 # Skip objtool for LLVM bitcode
 $(obj)/%.o: objtool-enabled :=
 
-# objtool was skipped for LLVM bitcode, run it now that we have compiled
-# modules into native code
-$(obj)/%.lto.o: objtool-enabled = y
-$(obj)/%.lto.o: part-of-module := y
-
-else ifdef CONFIG_X86_KERNEL_IBT
-
-# Skip objtool on individual files
-$(obj)/%.o: objtool-enabled :=
-
-# instead run objtool on the module as a whole, right before
-# the final link pass with the linker script.
-$(obj)/%.objtool: objtool-enabled = y
-$(obj)/%.objtool: part-of-module := y
-
 else
 
 # 'OBJECT_FILES_NON_STANDARD := y': skip objtool checking for a directory
@@ -310,19 +289,24 @@ $(obj)/%.o: $(src)/%.c $(recordmcount_source) FORCE
 	$(call if_changed_rule,cc_o_c)
 	$(call cmd,force_checksrc)
 
-ifdef CONFIG_LTO_CLANG
+ifneq ($(CONFIG_LTO_CLANG)$(CONFIG_X86_KERNEL_IBT),)
 # Module .o files may contain LLVM bitcode, compile them into native code
 # before ELF processing
-quiet_cmd_cc_lto_link_modules = LTO [M] $@
-      cmd_cc_lto_link_modules =						\
+quiet_cmd_cc_prelink_modules = LD [M]  $@
+      cmd_cc_prelink_modules =						\
 	$(LD) $(ld_flags) -r -o $@					\
-		$(shell [ -s $(@:.lto.o=.o.symversions) ] &&		\
-			echo -T $(@:.lto.o=.o.symversions))		\
+               $(shell [ -s $(@:.prelink.o=.o.symversions) ] &&		\
+                       echo -T $(@:.prelink.o=.o.symversions))		\
 		--whole-archive $(filter-out FORCE,$^)			\
 		$(cmd_objtool)
 
-$(obj)/%.lto.o: $(obj)/%.o FORCE
-	$(call if_changed,cc_lto_link_modules)
+# objtool was skipped for LLVM bitcode, run it now that we have compiled
+# modules into native code
+$(obj)/%.prelink.o: objtool-enabled = y
+$(obj)/%.prelink.o: part-of-module := y
+
+$(obj)/%.prelink.o: $(obj)/%.o FORCE
+	$(call if_changed,cc_prelink_modules)
 endif
 
 cmd_mod = { \
@@ -333,18 +317,6 @@ cmd_mod = { \
 $(obj)/%.mod: $(obj)/%$(mod-prelink-ext).o FORCE
 	$(call if_changed,mod)
 
-#
-# Since objtool will re-write the file it will change the timestamps, therefore
-# it is critical that the %.objtool file gets a timestamp *after* objtool runs.
-#
-# Additionally, care must be had with ordering this rule against the other rules
-# that take %.o as a dependency.
-#
-cmd_objtool_mod = true $(cmd_objtool) ; touch $@
-
-$(obj)/%.objtool: $(obj)/%$(mod-prelink-ext).o FORCE
-	$(call if_changed,objtool_mod)
-
 quiet_cmd_cc_lst_c = MKLST   $@
       cmd_cc_lst_c = $(CC) $(c_flags) -g -c -o $*.o $< && \
 		     $(CONFIG_SHELL) $(srctree)/scripts/makelst $*.o \
@@ -498,7 +470,7 @@ $(obj)/lib.a: $(lib-y) FORCE
 # Do not replace $(filter %.o,^) with $(real-prereqs). When a single object
 # module is turned into a multi object module, $^ will contain header file
 # dependencies recorded in the .*.cmd file.
-ifdef CONFIG_LTO_CLANG
+ifneq ($(CONFIG_LTO_CLANG)$(CONFIG_X86_KERNEL_IBT),)
 quiet_cmd_link_multi-m = AR [M]  $@
 cmd_link_multi-m =						\
 	$(cmd_update_lto_symversions);				\

scripts/Makefile.lib

@@ -230,11 +230,11 @@ dtc_cpp_flags  = -Wp,-MMD,$(depfile).pre.tmp -nostdinc                    \
 		 $(addprefix -I,$(DTC_INCLUDE))                          \
 		 -undef -D__DTS__
 
-ifeq ($(CONFIG_LTO_CLANG),y)
+ifneq ($(CONFIG_LTO_CLANG)$(CONFIG_X86_KERNEL_IBT),)
 # With CONFIG_LTO_CLANG, .o files in modules might be LLVM bitcode, so we
 # need to run LTO to compile them into native code (.lto.o) before further
 # processing.
-mod-prelink-ext := .lto
+mod-prelink-ext := .prelink
 endif
 
 # Useful for describing the dependency of composite objects

scripts/mod/modpost.c

@@ -1989,9 +1989,9 @@ static char *remove_dot(char *s)
 		if (m && (s[n + m] == '.' || s[n + m] == 0))
 			s[n] = 0;
 
-		/* strip trailing .lto */
-		if (strends(s, ".lto"))
-			s[strlen(s) - 4] = '\0';
+		/* strip trailing .prelink */
+		if (strends(s, ".prelink"))
+			s[strlen(s) - 8] = '\0';
 	}
 	return s;
 }
@@ -2015,9 +2015,9 @@ static void read_symbols(const char *modname)
 		/* strip trailing .o */
 		tmp = NOFAIL(strdup(modname));
 		tmp[strlen(tmp) - 2] = '\0';
-		/* strip trailing .lto */
-		if (strends(tmp, ".lto"))
-			tmp[strlen(tmp) - 4] = '\0';
+		/* strip trailing .prelink */
+		if (strends(tmp, ".prelink"))
+			tmp[strlen(tmp) - 8] = '\0';
 		mod = new_module(tmp);
 		free(tmp);
 	}