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/*
* Copyright (c) 2014-2017 Richard Braun.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*
* Per-CPU variables.
*
* This module supports statically allocated per-CPU variables only. Each
* active processor gets its own block of pages, called percpu area, where
* percpu variables are stored. The offset of a percpu variable is fixed
* and added to the base of the percpu area to obtain the real address of
* the variable.
*
* A statically allocated percpu variable should be defined with the
* __percpu macro, e.g. :
*
* struct s var __percpu;
*
* Obviously, the variable cannot be directly accessed. Instead, percpu
* variables can be accessed with the following accessors :
* - percpu_ptr()
* - percpu_var()
*
* The cpu module is expected to provide the following accessors to access
* percpu variables from the local processor :
* - cpu_local_ptr()
* - cpu_local_var()
*
* These accessors may generate optimized code.
*
* Architecture-specific code must enforce that the percpu section starts
* at 0, thereby making the addresses of percpu variables offsets into the
* percpu area. It must also make sure the _percpu and _percpu_end symbols
* have valid virtual addresses, included between _init (but not part of
* the init section) and _end.
*
* Unless otherwise specified, accessing a percpu variable is not
* interrupt-safe.
*/
#ifndef _KERN_PERCPU_H
#define _KERN_PERCPU_H
#include <assert.h>
#include <stddef.h>
#include <stdint.h>
#include <kern/init.h>
#include <kern/macros.h>
#define PERCPU_SECTION .percpu
#define __percpu __section(QUOTE(PERCPU_SECTION))
/*
* Boundaries of the percpu section.
*
* The addresses of these symbols must be valid, even if the percpu section
* itself has different addresses.
*/
extern char _percpu;
extern char _percpu_end;
/*
* Expands to the address of a percpu variable.
*/
#define percpu_ptr(var, cpu) \
((typeof(var) *)(percpu_area(cpu) + ((uintptr_t)(&(var)))))
/*
* Expands to the lvalue of a percpu variable.
*/
#define percpu_var(var, cpu) (*(percpu_ptr(var, cpu)))
static inline void *
percpu_area(unsigned int cpu)
{
extern void *percpu_areas[CONFIG_MAX_CPUS];
void *area;
assert(cpu < CONFIG_MAX_CPUS);
area = percpu_areas[cpu];
assert(area != NULL);
return area;
}
/*
* Register a processor.
*
* This function creates a percpu area from kernel virtual memory for the
* given processor. The created area is filled from the content of the
* percpu section.
*/
int percpu_add(unsigned int cpu);
/*
* This init operation provides :
* - percpu section is registered as the BSP percpu area
*/
INIT_OP_DECLARE(percpu_bootstrap);
/*
* This init operation provides :
* - new percpu areas can be created
*/
INIT_OP_DECLARE(percpu_setup);
#endif /* _KERN_PERCPU_H */
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