Merge patch series "Prevent dynamic relocations in vDSO"

The first is a fix and the second a check to make sure we don't
regress on the relocations, so I'm picking this up as a series to get
the fix into fixes.

* b4-shazam-merge:
  riscv: Check that vdso does not contain any dynamic relocations
  riscv: vdso: Prevent the compiler from inserting calls to memset()

Link: https://lore.kernel.org/r/20241016083625.136311-1-alexghiti@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

arch/riscv/kernel/vdso/Makefile

@@ -18,6 +18,7 @@ obj-vdso = $(patsubst %, %.o, $(vdso-syms)) note.o
 
 ccflags-y := -fno-stack-protector
 ccflags-y += -DDISABLE_BRANCH_PROFILING
+ccflags-y += -fno-builtin
 
 ifneq ($(c-gettimeofday-y),)
   CFLAGS_vgettimeofday.o += -fPIC -include $(c-gettimeofday-y)
@@ -44,7 +45,7 @@ $(obj)/vdso.o: $(obj)/vdso.so
 
 # link rule for the .so file, .lds has to be first
 $(obj)/vdso.so.dbg: $(obj)/vdso.lds $(obj-vdso) FORCE
-	$(call if_changed,vdsold)
+	$(call if_changed,vdsold_and_check)
 LDFLAGS_vdso.so.dbg = -shared -soname=linux-vdso.so.1 \
 	--build-id=sha1 --hash-style=both --eh-frame-hdr
 
@@ -64,7 +65,8 @@ include/generated/vdso-offsets.h: $(obj)/vdso.so.dbg FORCE
 # actual build commands
 # The DSO images are built using a special linker script
 # Make sure only to export the intended __vdso_xxx symbol offsets.
-quiet_cmd_vdsold = VDSOLD  $@
-      cmd_vdsold = $(LD) $(ld_flags) -T $(filter-out FORCE,$^) -o $@.tmp && \
+quiet_cmd_vdsold_and_check = VDSOLD  $@
+      cmd_vdsold_and_check = $(LD) $(ld_flags) -T $(filter-out FORCE,$^) -o $@.tmp && \
                    $(OBJCOPY) $(patsubst %, -G __vdso_%, $(vdso-syms)) $@.tmp $@ && \
-                   rm $@.tmp
+                   rm $@.tmp && \
+                   $(cmd_vdso_check)