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Hao Ge
59b5ed409d
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/[email protected] Signed-off-by: Hao Ge <[email protected]> Suggested-by: Suren Baghdasaryan <[email protected]> Acked-by: Alexander Gordeev <[email protected]> [s390] Acked-by: Mike Rapoport (Microsoft) <[email protected]> Cc: Chistoph Lameter <[email protected]> Cc: Christian Borntraeger <[email protected]> Cc: David Hildenbrand <[email protected]> Cc: Dennis Zhou <[email protected]> Cc: Heiko Carstens <[email protected]> Cc: Kent Overstreet <[email protected]> Cc: Liam Howlett <[email protected]> Cc: Lorenzo Stoakes <[email protected]> Cc: Matt Turner <[email protected]> Cc: Richard Henderson <[email protected]> Cc: Sven Schnelle <[email protected]> Cc: Tejun Heo <[email protected]> Cc: Vasily Gorbik <[email protected]> Cc: Vlastimil Babka <[email protected]> Signed-off-by: Andrew Morton <[email protected]>
19 lines
532 B
C
19 lines
532 B
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef __ALPHA_PERCPU_H
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#define __ALPHA_PERCPU_H
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/*
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* To calculate addresses of locally defined variables, GCC uses
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* 32-bit displacement from the GP. Which doesn't work for per cpu
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* variables in modules, as an offset to the kernel per cpu area is
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* way above 4G.
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*
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* Always use weak definitions for percpu variables in modules.
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* Therefore, we have enabled CONFIG_ARCH_MODULE_NEEDS_WEAK_PER_CPU
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* in the Kconfig.
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*/
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#include <asm-generic/percpu.h>
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#endif /* __ALPHA_PERCPU_H */
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