arch/loongarch/kernel/vdso.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Author: Huacai Chen <[email protected]>
   4  * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
   5  */
   6
   7 #include <linux/binfmts.h>
   8 #include <linux/elf.h>
   9 #include <linux/err.h>
  10 #include <linux/init.h>
  11 #include <linux/ioport.h>
  12 #include <linux/kernel.h>
  13 #include <linux/mm.h>
  14 #include <linux/random.h>
  15 #include <linux/sched.h>
  16 #include <linux/slab.h>
  17 #include <linux/time_namespace.h>
  18
  19 #include <asm/page.h>
  20 #include <asm/vdso.h>
  21 #include <vdso/helpers.h>
  22 #include <vdso/vsyscall.h>
  23 #include <vdso/datapage.h>
  24 #include <generated/vdso-offsets.h>
  25
  26 extern char vdso_start[], vdso_end[];
  27
  28 /* Kernel-provided data used by the VDSO. */
  29 static union vdso_data_store generic_vdso_data __page_aligned_data;
  30
  31 static union {
  32         u8 page[LOONGARCH_VDSO_DATA_SIZE];
  33         struct loongarch_vdso_data vdata;
  34 } loongarch_vdso_data __page_aligned_data;
  35
  36 struct vdso_data *vdso_data = generic_vdso_data.data;
  37 struct vdso_pcpu_data *vdso_pdata = loongarch_vdso_data.vdata.pdata;
  38 struct vdso_rng_data *vdso_rng_data = &loongarch_vdso_data.vdata.rng_data;
  39
  40 static int vdso_mremap(const struct vm_special_mapping *sm, struct vm_area_struct *new_vma)
  41 {
  42         current->mm->context.vdso = (void *)(new_vma->vm_start);
  43
  44         return 0;
  45 }
  46
  47 static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
  48                              struct vm_area_struct *vma, struct vm_fault *vmf)
  49 {
  50         unsigned long pfn;
  51         struct page *timens_page = find_timens_vvar_page(vma);
  52
  53         switch (vmf->pgoff) {
  54         case VVAR_GENERIC_PAGE_OFFSET:
  55                 if (!timens_page)
  56                         pfn = sym_to_pfn(vdso_data);
  57                 else
  58                         pfn = page_to_pfn(timens_page);
  59                 break;
  60 #ifdef CONFIG_TIME_NS
  61         case VVAR_TIMENS_PAGE_OFFSET:
  62                 /*
  63                  * If a task belongs to a time namespace then a namespace specific
  64                  * VVAR is mapped with the VVAR_GENERIC_PAGE_OFFSET and the real
  65                  * VVAR page is mapped with the VVAR_TIMENS_PAGE_OFFSET offset.
  66                  * See also the comment near timens_setup_vdso_data().
  67                  */
  68                 if (!timens_page)
  69                         return VM_FAULT_SIGBUS;
  70                 else
  71                         pfn = sym_to_pfn(vdso_data);
  72                 break;
  73 #endif /* CONFIG_TIME_NS */
  74         case VVAR_LOONGARCH_PAGES_START ... VVAR_LOONGARCH_PAGES_END:
  75                 pfn = sym_to_pfn(&loongarch_vdso_data) + vmf->pgoff - VVAR_LOONGARCH_PAGES_START;
  76                 break;
  77         default:
  78                 return VM_FAULT_SIGBUS;
  79         }
  80
  81         return vmf_insert_pfn(vma, vmf->address, pfn);
  82 }
  83
  84 struct loongarch_vdso_info vdso_info = {
  85         .vdso = vdso_start,
  86         .code_mapping = {
  87                 .name = "[vdso]",
  88                 .mremap = vdso_mremap,
  89         },
  90         .data_mapping = {
  91                 .name = "[vvar]",
  92                 .fault = vvar_fault,
  93         },
  94         .offset_sigreturn = vdso_offset_sigreturn,
  95 };
  96
  97 static int __init init_vdso(void)
  98 {
  99         unsigned long i, cpu, pfn;
 100
 101         BUG_ON(!PAGE_ALIGNED(vdso_info.vdso));
 102
 103         for_each_possible_cpu(cpu)
 104                 vdso_pdata[cpu].node = cpu_to_node(cpu);
 105
 106         vdso_info.size = PAGE_ALIGN(vdso_end - vdso_start);
 107         vdso_info.code_mapping.pages =
 108                 kcalloc(vdso_info.size / PAGE_SIZE, sizeof(struct page *), GFP_KERNEL);
 109
 110         pfn = __phys_to_pfn(__pa_symbol(vdso_info.vdso));
 111         for (i = 0; i < vdso_info.size / PAGE_SIZE; i++)
 112                 vdso_info.code_mapping.pages[i] = pfn_to_page(pfn + i);
 113
 114         return 0;
 115 }
 116 subsys_initcall(init_vdso);
 117
 118 #ifdef CONFIG_TIME_NS
 119 struct vdso_data *arch_get_vdso_data(void *vvar_page)
 120 {
 121         return (struct vdso_data *)(vvar_page);
 122 }
 123
 124 /*
 125  * The vvar mapping contains data for a specific time namespace, so when a
 126  * task changes namespace we must unmap its vvar data for the old namespace.
 127  * Subsequent faults will map in data for the new namespace.
 128  *
 129  * For more details see timens_setup_vdso_data().
 130  */
 131 int vdso_join_timens(struct task_struct *task, struct time_namespace *ns)
 132 {
 133         struct mm_struct *mm = task->mm;
 134         struct vm_area_struct *vma;
 135
 136         VMA_ITERATOR(vmi, mm, 0);
 137
 138         mmap_read_lock(mm);
 139         for_each_vma(vmi, vma) {
 140                 if (vma_is_special_mapping(vma, &vdso_info.data_mapping))
 141                         zap_vma_pages(vma);
 142         }
 143         mmap_read_unlock(mm);
 144
 145         return 0;
 146 }
 147 #endif
 148
 149 static unsigned long vdso_base(void)
 150 {
 151         unsigned long base = STACK_TOP;
 152
 153         if (current->flags & PF_RANDOMIZE) {
 154                 base += get_random_u32_below(VDSO_RANDOMIZE_SIZE);
 155                 base = PAGE_ALIGN(base);
 156         }
 157
 158         return base;
 159 }
 160
 161 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 162 {
 163         int ret;
 164         unsigned long size, data_addr, vdso_addr;
 165         struct mm_struct *mm = current->mm;
 166         struct vm_area_struct *vma;
 167         struct loongarch_vdso_info *info = current->thread.vdso;
 168
 169         if (mmap_write_lock_killable(mm))
 170                 return -EINTR;
 171
 172         /*
 173          * Determine total area size. This includes the VDSO data itself
 174          * and the data pages.
 175          */
 176         size = VVAR_SIZE + info->size;
 177
 178         data_addr = get_unmapped_area(NULL, vdso_base(), size, 0, 0);
 179         if (IS_ERR_VALUE(data_addr)) {
 180                 ret = data_addr;
 181                 goto out;
 182         }
 183
 184         vma = _install_special_mapping(mm, data_addr, VVAR_SIZE,
 185                                        VM_READ | VM_MAYREAD | VM_PFNMAP,
 186                                        &info->data_mapping);
 187         if (IS_ERR(vma)) {
 188                 ret = PTR_ERR(vma);
 189                 goto out;
 190         }
 191
 192         vdso_addr = data_addr + VVAR_SIZE;
 193         vma = _install_special_mapping(mm, vdso_addr, info->size,
 194                                        VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
 195                                        &info->code_mapping);
 196         if (IS_ERR(vma)) {
 197                 ret = PTR_ERR(vma);
 198                 goto out;
 199         }
 200
 201         mm->context.vdso = (void *)vdso_addr;
 202         ret = 0;
 203
 204 out:
 205         mmap_write_unlock(mm);
 206         return ret;
 207 }