x86/vdso: Provide getcpu for x86-32.

Wire up __vdso_getcpu() for x86-32.

The 64bit version is reused with trivial modifications. Contrary to
vclock_gettime.c there is no requirement to fake any defines in the case of
32bit VDSO on a 64bit kernel because the GDT entry from which the CPU and
node information is read is always the native one.

Adopt vdso_getcpu.c by:

 - removing the unneeded time* header files which lead to compile errors
   for 32bit.
 - adding segment.h which provides vdso_read_cpunode() and the defines
   required by it.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20221125094216.3663444-3-bigeasy@linutronix.de

arch/x86/entry/vdso/Makefile

@@ -29,7 +29,7 @@ VDSO32-$(CONFIG_IA32_EMULATION)	:= y
 # files to link into the vdso
 vobjs-y := vdso-note.o vclock_gettime.o vgetcpu.o
 vobjs32-y := vdso32/note.o vdso32/system_call.o vdso32/sigreturn.o
-vobjs32-y += vdso32/vclock_gettime.o
+vobjs32-y += vdso32/vclock_gettime.o vdso32/vgetcpu.o
 vobjs-$(CONFIG_X86_SGX)	+= vsgx.o
 
 # files to link into kernel
@@ -104,6 +104,7 @@ $(vobjs): KBUILD_AFLAGS += -DBUILD_VDSO
 CFLAGS_REMOVE_vclock_gettime.o = -pg
 CFLAGS_REMOVE_vdso32/vclock_gettime.o = -pg
 CFLAGS_REMOVE_vgetcpu.o = -pg
+CFLAGS_REMOVE_vdso32/vgetcpu.o = -pg
 CFLAGS_REMOVE_vsgx.o = -pg
 
 #

arch/x86/entry/vdso/vdso32/vdso32.lds.S

@@ -28,6 +28,7 @@ VERSION
 		__vdso_time;
 		__vdso_clock_getres;
 		__vdso_clock_gettime64;
+		__vdso_getcpu;
 	};
 
 	LINUX_2.5 {

arch/x86/entry/vdso/vdso32/vgetcpu.c

+// SPDX-License-Identifier: GPL-2.0
+#include "../vgetcpu.c"

arch/x86/entry/vdso/vgetcpu.c

@@ -7,8 +7,7 @@
 
 #include <linux/kernel.h>
 #include <linux/getcpu.h>
-#include <linux/time.h>
-#include <asm/vgtod.h>
+#include <asm/segment.h>
 
 notrace long
 __vdso_getcpu(unsigned *cpu, unsigned *node, struct getcpu_cache *unused)