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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* This file contains the routines for handling the MMU on those
* PowerPC implementations where the MMU substantially follows the
* architecture specification. This includes the 6xx, 7xx, 7xxx,
* and 8260 implementations but excludes the 8xx and 4xx.
* -- paulus
*
* Derived from arch/ppc/mm/init.c:
* Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
*
* Modifications by Paul Mackerras (PowerMac) (paulus@cs.anu.edu.au)
* and Cort Dougan (PReP) (cort@cs.nmt.edu)
* Copyright (C) 1996 Paul Mackerras
*
* Derived from "arch/i386/mm/init.c"
* Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
*/
#include <linux/mm.h>
#include <linux/init.h>
#include <linux/export.h>
#include <asm/mmu_context.h>
/*
* Room for two PTE pointers, usually the kernel and current user pointers
* to their respective root page table.
*/
void *abatron_pteptrs[2];
/*
* On 32-bit PowerPC 6xx/7xx/7xxx CPUs, we use a set of 16 VSIDs
* (virtual segment identifiers) for each context. Although the
* hardware supports 24-bit VSIDs, and thus >1 million contexts,
* we only use 32,768 of them. That is ample, since there can be
* at most around 30,000 tasks in the system anyway, and it means
* that we can use a bitmap to indicate which contexts are in use.
* Using a bitmap means that we entirely avoid all of the problems
* that we used to have when the context number overflowed,
* particularly on SMP systems.
* -- paulus.
*/
#define NO_CONTEXT ((unsigned long) -1)
#define LAST_CONTEXT 32767
#define FIRST_CONTEXT 1
static unsigned long next_mmu_context;
static unsigned long context_map[LAST_CONTEXT / BITS_PER_LONG + 1];
unsigned long __init_new_context(void)
{
unsigned long ctx = next_mmu_context;
while (test_and_set_bit(ctx, context_map)) {
ctx = find_next_zero_bit(context_map, LAST_CONTEXT+1, ctx);
if (ctx > LAST_CONTEXT)
ctx = 0;
}
next_mmu_context = (ctx + 1) & LAST_CONTEXT;
return ctx;
}
EXPORT_SYMBOL_GPL(__init_new_context);
/*
* Set up the context for a new address space.
*/
int init_new_context(struct task_struct *t, struct mm_struct *mm)
{
mm->context.id = __init_new_context();
mm->context.sr0 = CTX_TO_VSID(mm->context.id, 0);
if (!kuep_is_disabled())
mm->context.sr0 |= SR_NX;
if (!kuap_is_disabled())
mm->context.sr0 |= SR_KS;
return 0;
}
/*
* Free a context ID. Make sure to call this with preempt disabled!
*/
void __destroy_context(unsigned long ctx)
{
clear_bit(ctx, context_map);
}
EXPORT_SYMBOL_GPL(__destroy_context);
/*
* We're finished using the context for an address space.
*/
void destroy_context(struct mm_struct *mm)
{
preempt_disable();
if (mm->context.id != NO_CONTEXT) {
__destroy_context(mm->context.id);
mm->context.id = NO_CONTEXT;
}
preempt_enable();
}
/*
* Initialize the context management stuff.
*/
void __init mmu_context_init(void)
{
/* Reserve context 0 for kernel use */
context_map[0] = (1 << FIRST_CONTEXT) - 1;
next_mmu_context = FIRST_CONTEXT;
}
void switch_mmu_context(struct mm_struct *prev, struct mm_struct *next, struct task_struct *tsk)
{
long id = next->context.id;
if (id < 0)
panic("mm_struct %p has no context ID", next);
isync();
update_user_segments(next->context.sr0);
if (IS_ENABLED(CONFIG_BDI_SWITCH))
abatron_pteptrs[1] = next->pgd;
if (!mmu_has_feature(MMU_FTR_HPTE_TABLE))
mtspr(SPRN_SDR1, rol32(__pa(next->pgd), 4) & 0xffff01ff);
mb(); /* sync */
isync();
}
EXPORT_SYMBOL(switch_mmu_context);
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