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