Messages in this thread Patch in this message | | | From | Xin Li <> | Subject | [PATCH v2 1/1] x86/vdso: choose the right GDT_ENTRY_CPUNODE for 32-bit getcpu() on 64-bit kernel | Date | Tue, 21 Mar 2023 23:17:58 -0700 |
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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@intel.com> https://lore.kernel.org/oe-lkp/202303020903.b01fd1de-yujie.liu@intel.com/ Reported-by: Shan Kang <shan.kang@intel.com> Signed-off-by: Xin Li <xin3.li@intel.com> ---
Change since v1: * Define all of the GDT_ENTRY_* macros in *one* place, then make that *one* place depend on BUILD_VDSO32_64 (Dave Hansen). --- 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 794f69625780..9d6411c65920 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: * -- 2.34.1
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