x86/vdso: Choose the right GDT_ENTRY_CPUNODE for 32-bit getcpu() on 6…

…4-bit kernel

commit 39163d5 upstream.

The vDSO getcpu() reads CPU ID from the GDT_ENTRY_CPUNODE entry when the RDPID
instruction is not available. And GDT_ENTRY_CPUNODE is defined as 28 on 32-bit
Linux kernel and 15 on 64-bit. But the 32-bit getcpu() on 64-bit Linux kernel
is compiled with 32-bit Linux kernel GDT_ENTRY_CPUNODE, i.e., 28, beyond the
64-bit Linux kernel GDT limit. Thus, it just fails _silently_.

When BUILD_VDSO32_64 is defined, choose the 64-bit Linux kernel GDT definitions
to compile the 32-bit getcpu().

Fixes: 877cff5 ("x86/vdso: Fake 32bit VDSO build on 64bit compile for vgetcpu")
Reported-by: kernel test robot <yujie.liu@intel.com>
Reported-by: Shan Kang <shan.kang@intel.com>
Signed-off-by: Xin Li <xin3.li@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20230322061758.10639-1-xin3.li@intel.com
Link: https://lore.kernel.org/oe-lkp/202303020903.b01fd1de-yujie.liu@intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

arch/x86/include/asm/segment.h

@@ -56,7 +56,7 @@
 
 #define GDT_ENTRY_INVALID_SEG	0
 
-#ifdef CONFIG_X86_32
+#if defined(CONFIG_X86_32) && !defined(BUILD_VDSO32_64)
 /*
  * The layout of the per-CPU GDT under Linux:
  *