MIPS: Fix genvdso error on rebuild

The genvdso program modifies the debug and stripped versions of the
VDSOs in place, and errors if the modification has already taken place.
Unfortunately this means that a rebuild which tries to rerun genvdso to
generate vdso*-image.c without also rebuilding vdso.so.dbg (for example
if genvdso.c is modified) hits a build error like this:

arch/mips/vdso/genvdso 'arch/mips/vdso/vdso.so.dbg' already contains a '.MIPS.abiflags' section

This is fixed by reorganising the rules such that unmodified .so files
have a .raw suffix, and these are copied in the same rule that runs
genvdso on the copies.

I.e. previously we had:

 cmd_vdsold:
  link objects -> vdso.so.dbg

 cmd_genvdso:
  strip vdso.so.dbg -> vdso.so
  run genvdso -> vdso-image.c
   and modify vdso.so.dbg and vdso.so in place

Now we have:

 cmd_vdsold:
  link objects -> vdso.so.dbg.raw

 a new cmd_objcopy based strip rule (inspired by ARM):
  strip vdso.so.dbg.raw -> vdso.so.raw

 cmd_genvdso:
  copy vdso.so.dbg.raw -> vdso.so.dbg
  copy vdso.so.raw -> vdso.so
  run genvdso -> vdso-image.c
   and modify vdso.so.dbg and vdso.so in place

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/13250/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/vdso/Makefile

@@ -50,13 +50,17 @@ quiet_cmd_vdsold = VDSO    $@
       cmd_vdsold = $(CC) $(c_flags) $(VDSO_LDFLAGS) \
                    -Wl,-T $(filter %.lds,$^) $(filter %.o,$^) -o $@
 
+# Strip rule for the raw .so files
+$(obj)/%.so.raw: OBJCOPYFLAGS := -S
+$(obj)/%.so.raw: $(obj)/%.so.dbg.raw FORCE
+	$(call if_changed,objcopy)
+
 hostprogs-y := genvdso
 
 quiet_cmd_genvdso = GENVDSO $@
 define cmd_genvdso
-	cp $< $(<:%.dbg=%) && \
+	$(foreach file,$(filter %.raw,$^),cp $(file) $(file:%.raw=%) &&) \
-	$(OBJCOPY) -S $< $(<:%.dbg=%) && \
+	$(obj)/genvdso $(<:%.raw=%) $(<:%.dbg.raw=%) $@ $(VDSO_NAME)
-	$(obj)/genvdso $< $(<:%.dbg=%) $@ $(VDSO_NAME)
 endef
 
 #
@@ -66,7 +70,10 @@ endef
 native-abi := $(filter -mabi=%,$(KBUILD_CFLAGS))
 
 targets += $(obj-vdso-y)
-targets += vdso.lds vdso.so.dbg vdso.so vdso-image.c
+targets += vdso.lds
+targets += vdso.so.dbg.raw vdso.so.raw
+targets += vdso.so.dbg vdso.so
+targets += vdso-image.c
 
 obj-vdso := $(obj-vdso-y:%.o=$(obj)/%.o)
 
@@ -75,10 +82,11 @@ $(obj-vdso): KBUILD_AFLAGS := $(aflags-vdso) $(native-abi)
 
 $(obj)/vdso.lds: KBUILD_CPPFLAGS := $(native-abi)
 
-$(obj)/vdso.so.dbg: $(obj)/vdso.lds $(obj-vdso) FORCE
+$(obj)/vdso.so.dbg.raw: $(obj)/vdso.lds $(obj-vdso) FORCE
 	$(call if_changed,vdsold)
 
-$(obj)/vdso-image.c: $(obj)/vdso.so.dbg $(obj)/genvdso FORCE
+$(obj)/vdso-image.c: $(obj)/vdso.so.dbg.raw $(obj)/vdso.so.raw \
+                     $(obj)/genvdso FORCE
 	$(call if_changed,genvdso)
 
 obj-y += vdso-image.o
@@ -89,7 +97,10 @@ obj-y += vdso-image.o
 
 # Define these outside the ifdef to ensure they are picked up by clean.
 targets += $(obj-vdso-y:%.o=%-o32.o)
-targets += vdso-o32.lds vdso-o32.so.dbg vdso-o32.so vdso-o32-image.c
+targets += vdso-o32.lds
+targets += vdso-o32.so.dbg.raw vdso-o32.so.raw
+targets += vdso-o32.so.dbg vdso-o32.so
+targets += vdso-o32-image.c
 
 ifdef CONFIG_MIPS32_O32
 
@@ -109,11 +120,12 @@ $(obj)/vdso-o32.lds: KBUILD_CPPFLAGS := -mabi=32
 $(obj)/vdso-o32.lds: $(src)/vdso.lds.S FORCE
 	$(call if_changed_dep,cpp_lds_S)
 
-$(obj)/vdso-o32.so.dbg: $(obj)/vdso-o32.lds $(obj-vdso-o32) FORCE
+$(obj)/vdso-o32.so.dbg.raw: $(obj)/vdso-o32.lds $(obj-vdso-o32) FORCE
 	$(call if_changed,vdsold)
 
 $(obj)/vdso-o32-image.c: VDSO_NAME := o32
-$(obj)/vdso-o32-image.c: $(obj)/vdso-o32.so.dbg $(obj)/genvdso FORCE
+$(obj)/vdso-o32-image.c: $(obj)/vdso-o32.so.dbg.raw $(obj)/vdso-o32.so.raw \
+                         $(obj)/genvdso FORCE
 	$(call if_changed,genvdso)
 
 obj-y += vdso-o32-image.o
@@ -125,7 +137,10 @@ endif
 #
 
 targets += $(obj-vdso-y:%.o=%-n32.o)
-targets += vdso-n32.lds vdso-n32.so.dbg vdso-n32.so vdso-n32-image.c
+targets += vdso-n32.lds
+targets += vdso-n32.so.dbg.raw vdso-n32.so.raw
+targets += vdso-n32.so.dbg vdso-n32.so
+targets += vdso-n32-image.c
 
 ifdef CONFIG_MIPS32_N32
 
@@ -145,11 +160,12 @@ $(obj)/vdso-n32.lds: KBUILD_CPPFLAGS := -mabi=n32
 $(obj)/vdso-n32.lds: $(src)/vdso.lds.S FORCE
 	$(call if_changed_dep,cpp_lds_S)
 
-$(obj)/vdso-n32.so.dbg: $(obj)/vdso-n32.lds $(obj-vdso-n32) FORCE
+$(obj)/vdso-n32.so.dbg.raw: $(obj)/vdso-n32.lds $(obj-vdso-n32) FORCE
 	$(call if_changed,vdsold)
 
 $(obj)/vdso-n32-image.c: VDSO_NAME := n32
-$(obj)/vdso-n32-image.c: $(obj)/vdso-n32.so.dbg $(obj)/genvdso FORCE
+$(obj)/vdso-n32-image.c: $(obj)/vdso-n32.so.dbg.raw $(obj)/vdso-n32.so.raw \
+                         $(obj)/genvdso FORCE
 	$(call if_changed,genvdso)
 
 obj-y += vdso-n32-image.o