BACKPORT: arm64: vdso: use $(LD) instead of $(CC) to link VDSO

We use $(LD) to link vmlinux, modules, decompressors, etc.

VDSO is the only exceptional case where $(CC) is used as the linker
driver, but I do not know why we need to do so. VDSO uses a special
linker script, and does not link standard libraries at all.

I changed the Makefile to use $(LD) rather than $(CC). I tested this,
and VDSO worked for me.

Users will be able to use their favorite linker (e.g. lld instead of
of bfd) by passing LD= from the command line.

My plan is to rewrite all VDSO Makefiles to use $(LD), then delete
cc-ldoption.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
[panchajanya1999: cherry-pick and adapt to subsequent vdso32 changes from pixel]
[linked from: aosp-mirror/kernel_common@691efbe#diff-0aef76c20f8f6b0455c2de52956f5edb]
Signed-off-by: Panchajanya Sarkar <panchajanya@azure-dev.live>
Signed-off-by: Panchajanya1999 <panchajanya@azure-dev.live>

Change-Id: I4f4c67303c882987ba19bac1d98b21517dea770c
Signed-off-by: Panchajanya1999 <panchajanya@azure-dev.live>
Signed-off-by: Kyvangka1610 <kyvangka2002@gmail.com>

arch/arm64/kernel/vdso/Makefile

@@ -15,11 +15,9 @@ obj-vdso-s := $(addprefix $(obj)/, $(obj-vdso-s))
 obj-vdso-c := $(addprefix $(obj)/, $(obj-vdso-c))
 obj-vdso   := $(obj-vdso-c) $(obj-vdso-s)
 
-ccflags-y := -shared -fno-common -fno-builtin -fno-stack-protector
-ccflags-y += -DDISABLE_BRANCH_PROFILING -ffixed-x18
-ccflags-y += -nostdlib -Wl,-soname=linux-vdso.so.1 \
-		$(call cc-ldoption, -Wl$(comma)--hash-style=sysv)
-ccflags-y += $(DISABLE_LTO)
+ccflags-y := -fno-stack-protector -DDISABLE_BRANCH_PROFILING -ffixed-x18
+ldflags-y := -shared -nostdlib -soname=linux-vdso.so.1 \
+		$(call ld-option, --hash-style=sysv) -n -T
 
 # Force -O2 to avoid libgcc dependencies
 CFLAGS_REMOVE_vgettimeofday.o = -pg -Os
@@ -43,7 +41,7 @@ $(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,ld)
 
 # Strip rule for the .so file
 $(obj)/%.so: OBJCOPYFLAGS := -S
@@ -66,8 +64,6 @@ $(obj-vdso-c): %.o: %.c FORCE
 	$(call if_changed_dep,vdsocc)
 
 # Actual build commands
-quiet_cmd_vdsold = VDSOL   $@
-      cmd_vdsold = $(CC) $(c_flags) -Wl,-n -Wl,-T $(real-prereqs) -o $@
 quiet_cmd_vdsocc = VDSOC   $@
       cmd_vdsocc = ${CC} $(c_flags) -c -o $@ $<
 quiet_cmd_vdsoas = VDSOA   $@