b01e8dc343
alpha percpu access requires custom SHIFT_PERCPU_PTR() definition for modules to work around addressing range limitation. This is done via generating inline assembly using C preprocessing which forces the assembler to generate external reference. This happens behind the compiler's back and makes the compiler think that static percpu variables in modules are unused. This used to be worked around by using __unused attribute for percpu variables which prevent the compiler from omitting the variable; however, recent declare/definition attribute unification change broke this as __used can't be used for declaration. Also, in the process, PER_CPU_ATTRIBUTES definition in alpha percpu.h got broken. This patch adds PER_CPU_DEF_ATTRIBUTES which is only used for definitions and make alpha use it to add __used for percpu variables in modules. This also fixes the PER_CPU_ATTRIBUTES double definition bug. Signed-off-by: Tejun Heo <tj@kernel.org> Tested-by: maximilian attems <max@stro.at> Acked-by: Ivan Kokshaysky <ink@jurassic.park.msu.ru> Cc: Richard Henderson <rth@twiddle.net> Cc: <stable@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
103 lines
2.6 KiB
C
103 lines
2.6 KiB
C
#ifndef __ALPHA_PERCPU_H
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#define __ALPHA_PERCPU_H
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#include <linux/compiler.h>
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#include <linux/threads.h>
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#include <linux/percpu-defs.h>
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/*
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* Determine the real variable name from the name visible in the
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* kernel sources.
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*/
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#define per_cpu_var(var) per_cpu__##var
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#ifdef CONFIG_SMP
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/*
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* per_cpu_offset() is the offset that has to be added to a
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* percpu variable to get to the instance for a certain processor.
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*/
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extern unsigned long __per_cpu_offset[NR_CPUS];
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#define per_cpu_offset(x) (__per_cpu_offset[x])
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#define __my_cpu_offset per_cpu_offset(raw_smp_processor_id())
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#ifdef CONFIG_DEBUG_PREEMPT
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#define my_cpu_offset per_cpu_offset(smp_processor_id())
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#else
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#define my_cpu_offset __my_cpu_offset
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#endif
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#ifndef MODULE
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#define SHIFT_PERCPU_PTR(var, offset) RELOC_HIDE(&per_cpu_var(var), (offset))
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#define PER_CPU_DEF_ATTRIBUTES
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#else
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/*
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* To calculate addresses of locally defined variables, GCC uses 32-bit
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* displacement from the GP. Which doesn't work for per cpu variables in
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* modules, as an offset to the kernel per cpu area is way above 4G.
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*
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* This forces allocation of a GOT entry for per cpu variable using
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* ldq instruction with a 'literal' relocation.
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*/
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#define SHIFT_PERCPU_PTR(var, offset) ({ \
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extern int simple_identifier_##var(void); \
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unsigned long __ptr, tmp_gp; \
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asm ( "br %1, 1f \n\
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1: ldgp %1, 0(%1) \n\
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ldq %0, per_cpu__" #var"(%1)\t!literal" \
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: "=&r"(__ptr), "=&r"(tmp_gp)); \
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(typeof(&per_cpu_var(var)))(__ptr + (offset)); })
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#define PER_CPU_DEF_ATTRIBUTES __used
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#endif /* MODULE */
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/*
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* A percpu variable may point to a discarded regions. The following are
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* established ways to produce a usable pointer from the percpu variable
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* offset.
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*/
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#define per_cpu(var, cpu) \
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(*SHIFT_PERCPU_PTR(var, per_cpu_offset(cpu)))
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#define __get_cpu_var(var) \
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(*SHIFT_PERCPU_PTR(var, my_cpu_offset))
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#define __raw_get_cpu_var(var) \
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(*SHIFT_PERCPU_PTR(var, __my_cpu_offset))
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#else /* ! SMP */
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#define per_cpu(var, cpu) (*((void)(cpu), &per_cpu_var(var)))
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#define __get_cpu_var(var) per_cpu_var(var)
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#define __raw_get_cpu_var(var) per_cpu_var(var)
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#define PER_CPU_DEF_ATTRIBUTES
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#endif /* SMP */
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#ifdef CONFIG_SMP
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#define PER_CPU_BASE_SECTION ".data.percpu"
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#else
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#define PER_CPU_BASE_SECTION ".data"
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#endif
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#ifdef CONFIG_SMP
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#ifdef MODULE
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#define PER_CPU_SHARED_ALIGNED_SECTION ""
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#else
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#define PER_CPU_SHARED_ALIGNED_SECTION ".shared_aligned"
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#endif
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#define PER_CPU_FIRST_SECTION ".first"
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#else
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#define PER_CPU_SHARED_ALIGNED_SECTION ""
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#define PER_CPU_FIRST_SECTION ""
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#endif
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#define PER_CPU_ATTRIBUTES
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#endif /* __ALPHA_PERCPU_H */
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