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 */ 30 void *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 48 static unsigned long next_mmu_context; 49 static unsigned long context_map[LAST_CONTEXT / BITS_PER_LONG + 1]; 50 51 unsigned 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 } 64 EXPORT_SYMBOL_GPL(__init_new_context); 65 66 /* 67 * Set up the context for a new address space. 68 */ 69 int 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 (IS_ENABLED(CONFIG_PPC_KUEP)) 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 */ 85 void __destroy_context(unsigned long ctx) 86 { 87 clear_bit(ctx, context_map); 88 } 89 EXPORT_SYMBOL_GPL(__destroy_context); 90 91 /* 92 * We're finished using the context for an address space. 93 */ 94 void 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 */ 107 void __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 } 113 114 void 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 } 134 EXPORT_SYMBOL(switch_mmu_context); 135