From 59b5ed409d03bc8b7bb153d78afcd7cea9d7bbfa Mon Sep 17 00:00:00 2001 From: Hao Ge Date: Wed, 18 Jun 2025 09:58:09 +0800 Subject: mm/percpu: conditionally define _shared_alloc_tag via CONFIG_ARCH_MODULE_NEEDS_WEAK_PER_CPU Recently discovered this entry while checking kallsyms on ARM64: ffff800083e509c0 D _shared_alloc_tag If ARCH_NEEDS_WEAK_PER_CPU is not defined(it is only defined for s390 and alpha architectures), there's no need to statically define the percpu variable _shared_alloc_tag. Therefore, we need to implement isolation for this purpose. When building the core kernel code for s390 or alpha architectures, ARCH_NEEDS_WEAK_PER_CPU remains undefined (as it is gated by #if defined(MODULE)). However, when building modules for these architectures, the macro is explicitly defined. Therefore, we remove all instances of ARCH_NEEDS_WEAK_PER_CPU from the code and introduced CONFIG_ARCH_MODULE_NEEDS_WEAK_PER_CPU to replace the relevant logic. We can now conditionally define the perpcu variable _shared_alloc_tag based on CONFIG_ARCH_MODULE_NEEDS_WEAK_PER_CPU. This allows architectures (such as s390/alpha) that require weak definitions for percpu variables in modules to include the definition, while others can omit it via compile-time exclusion. Link: https://lkml.kernel.org/r/20250618015809.1235761-1-hao.ge@linux.dev Signed-off-by: Hao Ge Suggested-by: Suren Baghdasaryan Acked-by: Alexander Gordeev [s390] Acked-by: Mike Rapoport (Microsoft) Cc: Chistoph Lameter Cc: Christian Borntraeger Cc: David Hildenbrand Cc: Dennis Zhou Cc: Heiko Carstens Cc: Kent Overstreet Cc: Liam Howlett Cc: Lorenzo Stoakes Cc: Matt Turner Cc: Richard Henderson Cc: Sven Schnelle Cc: Tejun Heo Cc: Vasily Gorbik Cc: Vlastimil Babka Signed-off-by: Andrew Morton --- arch/alpha/Kconfig | 1 + arch/alpha/include/asm/percpu.h | 5 ++--- 2 files changed, 3 insertions(+), 3 deletions(-) (limited to 'arch/alpha') diff --git a/arch/alpha/Kconfig b/arch/alpha/Kconfig index 109a4cddcd13..80367f2cf821 100644 --- a/arch/alpha/Kconfig +++ b/arch/alpha/Kconfig @@ -7,6 +7,7 @@ config ALPHA select ARCH_HAS_DMA_OPS if PCI select ARCH_MIGHT_HAVE_PC_PARPORT select ARCH_MIGHT_HAVE_PC_SERIO + select ARCH_MODULE_NEEDS_WEAK_PER_CPU if SMP select ARCH_NO_PREEMPT select ARCH_NO_SG_CHAIN select ARCH_USE_CMPXCHG_LOCKREF diff --git a/arch/alpha/include/asm/percpu.h b/arch/alpha/include/asm/percpu.h index 6923249f2d49..4383d66341dc 100644 --- a/arch/alpha/include/asm/percpu.h +++ b/arch/alpha/include/asm/percpu.h @@ -9,10 +9,9 @@ * way above 4G. * * Always use weak definitions for percpu variables in modules. + * Therefore, we have enabled CONFIG_ARCH_MODULE_NEEDS_WEAK_PER_CPU + * in the Kconfig. */ -#if defined(MODULE) && defined(CONFIG_SMP) -#define ARCH_NEEDS_WEAK_PER_CPU -#endif #include -- cgit v1.2.3