1 // SPDX-License-Identifier: GPL-2.0 2 3 #include <linux/spinlock.h> 4 #include <linux/percpu.h> 5 6 #include <asm/cpu_entry_area.h> 7 #include <asm/pgtable.h> 8 #include <asm/fixmap.h> 9 #include <asm/desc.h> 10 11 static DEFINE_PER_CPU_PAGE_ALIGNED(struct entry_stack_page, entry_stack_storage); 12 13 #ifdef CONFIG_X86_64 14 static DEFINE_PER_CPU_PAGE_ALIGNED(char, exception_stacks 15 [(N_EXCEPTION_STACKS - 1) * EXCEPTION_STKSZ + DEBUG_STKSZ]); 16 #endif 17 18 struct cpu_entry_area *get_cpu_entry_area(int cpu) 19 { 20 unsigned long va = CPU_ENTRY_AREA_PER_CPU + cpu * CPU_ENTRY_AREA_SIZE; 21 BUILD_BUG_ON(sizeof(struct cpu_entry_area) % PAGE_SIZE != 0); 22 23 return (struct cpu_entry_area *) va; 24 } 25 EXPORT_SYMBOL(get_cpu_entry_area); 26 27 void cea_set_pte(void *cea_vaddr, phys_addr_t pa, pgprot_t flags) 28 { 29 unsigned long va = (unsigned long) cea_vaddr; 30 pte_t pte = pfn_pte(pa >> PAGE_SHIFT, flags); 31 32 /* 33 * The cpu_entry_area is shared between the user and kernel 34 * page tables. All of its ptes can safely be global. 35 * _PAGE_GLOBAL gets reused to help indicate PROT_NONE for 36 * non-present PTEs, so be careful not to set it in that 37 * case to avoid confusion. 38 */ 39 if (boot_cpu_has(X86_FEATURE_PGE) && 40 (pgprot_val(flags) & _PAGE_PRESENT)) 41 pte = pte_set_flags(pte, _PAGE_GLOBAL); 42 43 set_pte_vaddr(va, pte); 44 } 45 46 static void __init 47 cea_map_percpu_pages(void *cea_vaddr, void *ptr, int pages, pgprot_t prot) 48 { 49 for ( ; pages; pages--, cea_vaddr+= PAGE_SIZE, ptr += PAGE_SIZE) 50 cea_set_pte(cea_vaddr, per_cpu_ptr_to_phys(ptr), prot); 51 } 52 53 static void percpu_setup_debug_store(int cpu) 54 { 55 #ifdef CONFIG_CPU_SUP_INTEL 56 int npages; 57 void *cea; 58 59 if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL) 60 return; 61 62 cea = &get_cpu_entry_area(cpu)->cpu_debug_store; 63 npages = sizeof(struct debug_store) / PAGE_SIZE; 64 BUILD_BUG_ON(sizeof(struct debug_store) % PAGE_SIZE != 0); 65 cea_map_percpu_pages(cea, &per_cpu(cpu_debug_store, cpu), npages, 66 PAGE_KERNEL); 67 68 cea = &get_cpu_entry_area(cpu)->cpu_debug_buffers; 69 /* 70 * Force the population of PMDs for not yet allocated per cpu 71 * memory like debug store buffers. 72 */ 73 npages = sizeof(struct debug_store_buffers) / PAGE_SIZE; 74 for (; npages; npages--, cea += PAGE_SIZE) 75 cea_set_pte(cea, 0, PAGE_NONE); 76 #endif 77 } 78 79 /* Setup the fixmap mappings only once per-processor */ 80 static void __init setup_cpu_entry_area(int cpu) 81 { 82 #ifdef CONFIG_X86_64 83 extern char _entry_trampoline[]; 84 85 /* On 64-bit systems, we use a read-only fixmap GDT and TSS. */ 86 pgprot_t gdt_prot = PAGE_KERNEL_RO; 87 pgprot_t tss_prot = PAGE_KERNEL_RO; 88 #else 89 /* 90 * On native 32-bit systems, the GDT cannot be read-only because 91 * our double fault handler uses a task gate, and entering through 92 * a task gate needs to change an available TSS to busy. If the 93 * GDT is read-only, that will triple fault. The TSS cannot be 94 * read-only because the CPU writes to it on task switches. 95 * 96 * On Xen PV, the GDT must be read-only because the hypervisor 97 * requires it. 98 */ 99 pgprot_t gdt_prot = boot_cpu_has(X86_FEATURE_XENPV) ? 100 PAGE_KERNEL_RO : PAGE_KERNEL; 101 pgprot_t tss_prot = PAGE_KERNEL; 102 #endif 103 104 cea_set_pte(&get_cpu_entry_area(cpu)->gdt, get_cpu_gdt_paddr(cpu), 105 gdt_prot); 106 107 cea_map_percpu_pages(&get_cpu_entry_area(cpu)->entry_stack_page, 108 per_cpu_ptr(&entry_stack_storage, cpu), 1, 109 PAGE_KERNEL); 110 111 /* 112 * The Intel SDM says (Volume 3, 7.2.1): 113 * 114 * Avoid placing a page boundary in the part of the TSS that the 115 * processor reads during a task switch (the first 104 bytes). The 116 * processor may not correctly perform address translations if a 117 * boundary occurs in this area. During a task switch, the processor 118 * reads and writes into the first 104 bytes of each TSS (using 119 * contiguous physical addresses beginning with the physical address 120 * of the first byte of the TSS). So, after TSS access begins, if 121 * part of the 104 bytes is not physically contiguous, the processor 122 * will access incorrect information without generating a page-fault 123 * exception. 124 * 125 * There are also a lot of errata involving the TSS spanning a page 126 * boundary. Assert that we're not doing that. 127 */ 128 BUILD_BUG_ON((offsetof(struct tss_struct, x86_tss) ^ 129 offsetofend(struct tss_struct, x86_tss)) & PAGE_MASK); 130 BUILD_BUG_ON(sizeof(struct tss_struct) % PAGE_SIZE != 0); 131 cea_map_percpu_pages(&get_cpu_entry_area(cpu)->tss, 132 &per_cpu(cpu_tss_rw, cpu), 133 sizeof(struct tss_struct) / PAGE_SIZE, tss_prot); 134 135 #ifdef CONFIG_X86_32 136 per_cpu(cpu_entry_area, cpu) = get_cpu_entry_area(cpu); 137 #endif 138 139 #ifdef CONFIG_X86_64 140 BUILD_BUG_ON(sizeof(exception_stacks) % PAGE_SIZE != 0); 141 BUILD_BUG_ON(sizeof(exception_stacks) != 142 sizeof(((struct cpu_entry_area *)0)->exception_stacks)); 143 cea_map_percpu_pages(&get_cpu_entry_area(cpu)->exception_stacks, 144 &per_cpu(exception_stacks, cpu), 145 sizeof(exception_stacks) / PAGE_SIZE, PAGE_KERNEL); 146 147 cea_set_pte(&get_cpu_entry_area(cpu)->entry_trampoline, 148 __pa_symbol(_entry_trampoline), PAGE_KERNEL_RX); 149 #endif 150 percpu_setup_debug_store(cpu); 151 } 152 153 static __init void setup_cpu_entry_area_ptes(void) 154 { 155 #ifdef CONFIG_X86_32 156 unsigned long start, end; 157 158 BUILD_BUG_ON(CPU_ENTRY_AREA_PAGES * PAGE_SIZE < CPU_ENTRY_AREA_MAP_SIZE); 159 BUG_ON(CPU_ENTRY_AREA_BASE & ~PMD_MASK); 160 161 start = CPU_ENTRY_AREA_BASE; 162 end = start + CPU_ENTRY_AREA_MAP_SIZE; 163 164 /* Careful here: start + PMD_SIZE might wrap around */ 165 for (; start < end && start >= CPU_ENTRY_AREA_BASE; start += PMD_SIZE) 166 populate_extra_pte(start); 167 #endif 168 } 169 170 void __init setup_cpu_entry_areas(void) 171 { 172 unsigned int cpu; 173 174 setup_cpu_entry_area_ptes(); 175 176 for_each_possible_cpu(cpu) 177 setup_cpu_entry_area(cpu); 178 179 /* 180 * This is the last essential update to swapper_pgdir which needs 181 * to be synchronized to initial_page_table on 32bit. 182 */ 183 sync_initial_page_table(); 184 } 185