1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Copyright (C) 2015 Synopsys, Inc. (www.synopsys.com) 4 */ 5 6 #include <linux/memblock.h> 7 #include <linux/export.h> 8 #include <linux/highmem.h> 9 #include <asm/processor.h> 10 #include <asm/pgtable.h> 11 #include <asm/pgalloc.h> 12 #include <asm/tlbflush.h> 13 14 /* 15 * HIGHMEM API: 16 * 17 * kmap() API provides sleep semantics hence referred to as "permanent maps" 18 * It allows mapping LAST_PKMAP pages, using @last_pkmap_nr as the cursor 19 * for book-keeping 20 * 21 * kmap_atomic() can't sleep (calls pagefault_disable()), thus it provides 22 * shortlived ala "temporary mappings" which historically were implemented as 23 * fixmaps (compile time addr etc). Their book-keeping is done per cpu. 24 * 25 * Both these facts combined (preemption disabled and per-cpu allocation) 26 * means the total number of concurrent fixmaps will be limited to max 27 * such allocations in a single control path. Thus KM_TYPE_NR (another 28 * historic relic) is a small'ish number which caps max percpu fixmaps 29 * 30 * ARC HIGHMEM Details 31 * 32 * - the kernel vaddr space from 0x7z to 0x8z (currently used by vmalloc/module) 33 * is now shared between vmalloc and kmap (non overlapping though) 34 * 35 * - Both fixmap/pkmap use a dedicated page table each, hooked up to swapper PGD 36 * This means each only has 1 PGDIR_SIZE worth of kvaddr mappings, which means 37 * 2M of kvaddr space for typical config (8K page and 11:8:13 traversal split) 38 * 39 * - fixmap anyhow needs a limited number of mappings. So 2M kvaddr == 256 PTE 40 * slots across NR_CPUS would be more than sufficient (generic code defines 41 * KM_TYPE_NR as 20). 42 * 43 * - pkmap being preemptible, in theory could do with more than 256 concurrent 44 * mappings. However, generic pkmap code: map_new_virtual(), doesn't traverse 45 * the PGD and only works with a single page table @pkmap_page_table, hence 46 * sets the limit 47 */ 48 49 extern pte_t * pkmap_page_table; 50 static pte_t * fixmap_page_table; 51 52 void *kmap(struct page *page) 53 { 54 BUG_ON(in_interrupt()); 55 if (!PageHighMem(page)) 56 return page_address(page); 57 58 return kmap_high(page); 59 } 60 EXPORT_SYMBOL(kmap); 61 62 void *kmap_atomic(struct page *page) 63 { 64 int idx, cpu_idx; 65 unsigned long vaddr; 66 67 preempt_disable(); 68 pagefault_disable(); 69 if (!PageHighMem(page)) 70 return page_address(page); 71 72 cpu_idx = kmap_atomic_idx_push(); 73 idx = cpu_idx + KM_TYPE_NR * smp_processor_id(); 74 vaddr = FIXMAP_ADDR(idx); 75 76 set_pte_at(&init_mm, vaddr, fixmap_page_table + idx, 77 mk_pte(page, kmap_prot)); 78 79 return (void *)vaddr; 80 } 81 EXPORT_SYMBOL(kmap_atomic); 82 83 void __kunmap_atomic(void *kv) 84 { 85 unsigned long kvaddr = (unsigned long)kv; 86 87 if (kvaddr >= FIXMAP_BASE && kvaddr < (FIXMAP_BASE + FIXMAP_SIZE)) { 88 89 /* 90 * Because preemption is disabled, this vaddr can be associated 91 * with the current allocated index. 92 * But in case of multiple live kmap_atomic(), it still relies on 93 * callers to unmap in right order. 94 */ 95 int cpu_idx = kmap_atomic_idx(); 96 int idx = cpu_idx + KM_TYPE_NR * smp_processor_id(); 97 98 WARN_ON(kvaddr != FIXMAP_ADDR(idx)); 99 100 pte_clear(&init_mm, kvaddr, fixmap_page_table + idx); 101 local_flush_tlb_kernel_range(kvaddr, kvaddr + PAGE_SIZE); 102 103 kmap_atomic_idx_pop(); 104 } 105 106 pagefault_enable(); 107 preempt_enable(); 108 } 109 EXPORT_SYMBOL(__kunmap_atomic); 110 111 static noinline pte_t * __init alloc_kmap_pgtable(unsigned long kvaddr) 112 { 113 pgd_t *pgd_k; 114 p4d_t *p4d_k; 115 pud_t *pud_k; 116 pmd_t *pmd_k; 117 pte_t *pte_k; 118 119 pgd_k = pgd_offset_k(kvaddr); 120 p4d_k = p4d_offset(pgd_k, kvaddr); 121 pud_k = pud_offset(p4d_k, kvaddr); 122 pmd_k = pmd_offset(pud_k, kvaddr); 123 124 pte_k = (pte_t *)memblock_alloc_low(PAGE_SIZE, PAGE_SIZE); 125 if (!pte_k) 126 panic("%s: Failed to allocate %lu bytes align=0x%lx\n", 127 __func__, PAGE_SIZE, PAGE_SIZE); 128 129 pmd_populate_kernel(&init_mm, pmd_k, pte_k); 130 return pte_k; 131 } 132 133 void __init kmap_init(void) 134 { 135 /* Due to recursive include hell, we can't do this in processor.h */ 136 BUILD_BUG_ON(PAGE_OFFSET < (VMALLOC_END + FIXMAP_SIZE + PKMAP_SIZE)); 137 138 BUILD_BUG_ON(KM_TYPE_NR > PTRS_PER_PTE); 139 pkmap_page_table = alloc_kmap_pgtable(PKMAP_BASE); 140 141 BUILD_BUG_ON(LAST_PKMAP > PTRS_PER_PTE); 142 fixmap_page_table = alloc_kmap_pgtable(FIXMAP_BASE); 143 } 144