cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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mmu_context.c (3539B)

      1// SPDX-License-Identifier: GPL-2.0-or-later
      2/*
      3 * This file contains the routines for handling the MMU on those
      4 * PowerPC implementations where the MMU substantially follows the
      5 * architecture specification.  This includes the 6xx, 7xx, 7xxx,
      6 * and 8260 implementations but excludes the 8xx and 4xx.
      7 *  -- paulus
      8 *
      9 *  Derived from arch/ppc/mm/init.c:
     10 *    Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
     11 *
     12 *  Modifications by Paul Mackerras (PowerMac) (paulus@cs.anu.edu.au)
     13 *  and Cort Dougan (PReP) (cort@cs.nmt.edu)
     14 *    Copyright (C) 1996 Paul Mackerras
     15 *
     16 *  Derived from "arch/i386/mm/init.c"
     17 *    Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
     18 */
     19
     20#include <linux/mm.h>
     21#include <linux/init.h>
     22#include <linux/export.h>
     23
     24#include <asm/mmu_context.h>
     25
     26/*
     27 * Room for two PTE pointers, usually the kernel and current user pointers
     28 * to their respective root page table.
     29 */
     30void *abatron_pteptrs[2];
     31
     32/*
     33 * On 32-bit PowerPC 6xx/7xx/7xxx CPUs, we use a set of 16 VSIDs
     34 * (virtual segment identifiers) for each context.  Although the
     35 * hardware supports 24-bit VSIDs, and thus >1 million contexts,
     36 * we only use 32,768 of them.  That is ample, since there can be
     37 * at most around 30,000 tasks in the system anyway, and it means
     38 * that we can use a bitmap to indicate which contexts are in use.
     39 * Using a bitmap means that we entirely avoid all of the problems
     40 * that we used to have when the context number overflowed,
     41 * particularly on SMP systems.
     42 *  -- paulus.
     43 */
     44#define NO_CONTEXT      	((unsigned long) -1)
     45#define LAST_CONTEXT    	32767
     46#define FIRST_CONTEXT    	1
     47
     48static unsigned long next_mmu_context;
     49static unsigned long context_map[LAST_CONTEXT / BITS_PER_LONG + 1];
     50
     51unsigned long __init_new_context(void)
     52{
     53	unsigned long ctx = next_mmu_context;
     54
     55	while (test_and_set_bit(ctx, context_map)) {
     56		ctx = find_next_zero_bit(context_map, LAST_CONTEXT+1, ctx);
     57		if (ctx > LAST_CONTEXT)
     58			ctx = 0;
     59	}
     60	next_mmu_context = (ctx + 1) & LAST_CONTEXT;
     61
     62	return ctx;
     63}
     64EXPORT_SYMBOL_GPL(__init_new_context);
     65
     66/*
     67 * Set up the context for a new address space.
     68 */
     69int init_new_context(struct task_struct *t, struct mm_struct *mm)
     70{
     71	mm->context.id = __init_new_context();
     72	mm->context.sr0 = CTX_TO_VSID(mm->context.id, 0);
     73
     74	if (!kuep_is_disabled())
     75		mm->context.sr0 |= SR_NX;
     76	if (!kuap_is_disabled())
     77		mm->context.sr0 |= SR_KS;
     78
     79	return 0;
     80}
     81
     82/*
     83 * Free a context ID. Make sure to call this with preempt disabled!
     84 */
     85void __destroy_context(unsigned long ctx)
     86{
     87	clear_bit(ctx, context_map);
     88}
     89EXPORT_SYMBOL_GPL(__destroy_context);
     90
     91/*
     92 * We're finished using the context for an address space.
     93 */
     94void destroy_context(struct mm_struct *mm)
     95{
     96	preempt_disable();
     97	if (mm->context.id != NO_CONTEXT) {
     98		__destroy_context(mm->context.id);
     99		mm->context.id = NO_CONTEXT;
    100	}
    101	preempt_enable();
    102}
    103
    104/*
    105 * Initialize the context management stuff.
    106 */
    107void __init mmu_context_init(void)
    108{
    109	/* Reserve context 0 for kernel use */
    110	context_map[0] = (1 << FIRST_CONTEXT) - 1;
    111	next_mmu_context = FIRST_CONTEXT;
    112}
    113
    114void switch_mmu_context(struct mm_struct *prev, struct mm_struct *next, struct task_struct *tsk)
    115{
    116	long id = next->context.id;
    117
    118	if (id < 0)
    119		panic("mm_struct %p has no context ID", next);
    120
    121	isync();
    122
    123	update_user_segments(next->context.sr0);
    124
    125	if (IS_ENABLED(CONFIG_BDI_SWITCH))
    126		abatron_pteptrs[1] = next->pgd;
    127
    128	if (!mmu_has_feature(MMU_FTR_HPTE_TABLE))
    129		mtspr(SPRN_SDR1, rol32(__pa(next->pgd), 4) & 0xffff01ff);
    130
    131	mb();	/* sync */
    132	isync();
    133}
    134EXPORT_SYMBOL(switch_mmu_context);