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https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
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71995e4d00
This patch adds support for thread creation and context switching. Signed-off-by: Ley Foon Tan <lftan@altera.com>
116 lines
3 KiB
C
116 lines
3 KiB
C
/*
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* MMU context handling.
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*
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* Copyright (C) 2011 Tobias Klauser <tklauser@distanz.ch>
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* Copyright (C) 2009 Wind River Systems Inc
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* Implemented by fredrik.markstrom@gmail.com and ivarholmqvist@gmail.com
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*
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* This file is subject to the terms and conditions of the GNU General Public
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* License. See the file "COPYING" in the main directory of this archive
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* for more details.
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*/
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#include <linux/mm.h>
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#include <asm/cpuinfo.h>
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#include <asm/mmu_context.h>
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#include <asm/tlb.h>
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/* The pids position and mask in context */
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#define PID_SHIFT 0
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#define PID_BITS (cpuinfo.tlb_pid_num_bits)
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#define PID_MASK ((1UL << PID_BITS) - 1)
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/* The versions position and mask in context */
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#define VERSION_BITS (32 - PID_BITS)
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#define VERSION_SHIFT (PID_SHIFT + PID_BITS)
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#define VERSION_MASK ((1UL << VERSION_BITS) - 1)
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/* Return the version part of a context */
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#define CTX_VERSION(c) (((c) >> VERSION_SHIFT) & VERSION_MASK)
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/* Return the pid part of a context */
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#define CTX_PID(c) (((c) >> PID_SHIFT) & PID_MASK)
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/* Value of the first context (version 1, pid 0) */
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#define FIRST_CTX ((1UL << VERSION_SHIFT) | (0 << PID_SHIFT))
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static mm_context_t next_mmu_context;
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/*
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* Initialize MMU context management stuff.
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*/
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void __init mmu_context_init(void)
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{
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/* We need to set this here because the value depends on runtime data
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* from cpuinfo */
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next_mmu_context = FIRST_CTX;
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}
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/*
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* Set new context (pid), keep way
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*/
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static void set_context(mm_context_t context)
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{
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set_mmu_pid(CTX_PID(context));
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}
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static mm_context_t get_new_context(void)
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{
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/* Return the next pid */
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next_mmu_context += (1UL << PID_SHIFT);
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/* If the pid field wraps around we increase the version and
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* flush the tlb */
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if (unlikely(CTX_PID(next_mmu_context) == 0)) {
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/* Version is incremented since the pid increment above
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* overflows info version */
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flush_cache_all();
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flush_tlb_all();
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}
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/* If the version wraps we start over with the first generation, we do
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* not need to flush the tlb here since it's always done above */
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if (unlikely(CTX_VERSION(next_mmu_context) == 0))
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next_mmu_context = FIRST_CTX;
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return next_mmu_context;
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}
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void switch_mm(struct mm_struct *prev, struct mm_struct *next,
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struct task_struct *tsk)
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{
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unsigned long flags;
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local_irq_save(flags);
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/* If the process context we are swapping in has a different context
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* generation then we have it should get a new generation/pid */
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if (unlikely(CTX_VERSION(next->context) !=
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CTX_VERSION(next_mmu_context)))
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next->context = get_new_context();
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/* Save the current pgd so the fast tlb handler can find it */
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pgd_current = next->pgd;
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/* Set the current context */
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set_context(next->context);
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local_irq_restore(flags);
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}
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/*
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* After we have set current->mm to a new value, this activates
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* the context for the new mm so we see the new mappings.
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*/
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void activate_mm(struct mm_struct *prev, struct mm_struct *next)
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{
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next->context = get_new_context();
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set_context(next->context);
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pgd_current = next->pgd;
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}
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unsigned long get_pid_from_context(mm_context_t *context)
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{
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return CTX_PID((*context));
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}
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