The following commit has been merged into the x86/urgent branch of tip:
Commit-ID: 39163d5479285a36522b6e8f9cc568cc4987db08
Gitweb: https://git.kernel.org/tip/39163d5479285a36522b6e8f9cc568cc4987db08
Author: Xin Li <xin3.li@xxxxxxxxx>
AuthorDate: Tue, 21 Mar 2023 23:17:58 -07:00
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitterDate: Tue, 08 Aug 2023 09:31:43 +02:00
x86/vdso: Choose the right GDT_ENTRY_CPUNODE for 32-bit getcpu() on 64-bit kernel
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: 877cff5296faa6e ("x86/vdso: Fake 32bit VDSO build on 64bit compile for vgetcpu")
Reported-by: kernel test robot <yujie.liu@xxxxxxxxx>
Reported-by: Shan Kang <shan.kang@xxxxxxxxx>
Signed-off-by: Xin Li <xin3.li@xxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20230322061758.10639-1-xin3.li@xxxxxxxxx
Link: https://lore.kernel.org/oe-lkp/202303020903.b01fd1de-yujie.liu@xxxxxxxxx
---
arch/x86/include/asm/segment.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/segment.h b/arch/x86/include/asm/segment.h
index 794f696..9d6411c 100644
--- a/arch/x86/include/asm/segment.h
+++ b/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:
*
|