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Linux/arch/mips/kernel/vdso.c

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  1 // SPDX-License-Identifier: GPL-2.0-or-later
  2 /*
  3  * Copyright (C) 2015 Imagination Technologies
  4  * Author: Alex Smith <alex.smith@imgtec.com>
  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/timekeeper_internal.h>
 18 
 19 #include <asm/abi.h>
 20 #include <asm/mips-cps.h>
 21 #include <asm/page.h>
 22 #include <asm/vdso.h>
 23 #include <vdso/helpers.h>
 24 #include <vdso/vsyscall.h>
 25 
 26 /* Kernel-provided data used by the VDSO. */
 27 static union mips_vdso_data mips_vdso_data __page_aligned_data;
 28 struct vdso_data *vdso_data = mips_vdso_data.data;
 29 
 30 /*
 31  * Mapping for the VDSO data/GIC pages. The real pages are mapped manually, as
 32  * what we map and where within the area they are mapped is determined at
 33  * runtime.
 34  */
 35 static struct page *no_pages[] = { NULL };
 36 static struct vm_special_mapping vdso_vvar_mapping = {
 37         .name = "[vvar]",
 38         .pages = no_pages,
 39 };
 40 
 41 static void __init init_vdso_image(struct mips_vdso_image *image)
 42 {
 43         unsigned long num_pages, i;
 44         unsigned long data_pfn;
 45 
 46         BUG_ON(!PAGE_ALIGNED(image->data));
 47         BUG_ON(!PAGE_ALIGNED(image->size));
 48 
 49         num_pages = image->size / PAGE_SIZE;
 50 
 51         data_pfn = __phys_to_pfn(__pa_symbol(image->data));
 52         for (i = 0; i < num_pages; i++)
 53                 image->mapping.pages[i] = pfn_to_page(data_pfn + i);
 54 }
 55 
 56 static int __init init_vdso(void)
 57 {
 58         init_vdso_image(&vdso_image);
 59 
 60 #ifdef CONFIG_MIPS32_O32
 61         init_vdso_image(&vdso_image_o32);
 62 #endif
 63 
 64 #ifdef CONFIG_MIPS32_N32
 65         init_vdso_image(&vdso_image_n32);
 66 #endif
 67 
 68         return 0;
 69 }
 70 subsys_initcall(init_vdso);
 71 
 72 static unsigned long vdso_base(void)
 73 {
 74         unsigned long base = STACK_TOP;
 75 
 76         if (IS_ENABLED(CONFIG_MIPS_FP_SUPPORT)) {
 77                 /* Skip the delay slot emulation page */
 78                 base += PAGE_SIZE;
 79         }
 80 
 81         if (current->flags & PF_RANDOMIZE) {
 82                 base += get_random_int() & (VDSO_RANDOMIZE_SIZE - 1);
 83                 base = PAGE_ALIGN(base);
 84         }
 85 
 86         return base;
 87 }
 88 
 89 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 90 {
 91         struct mips_vdso_image *image = current->thread.abi->vdso;
 92         struct mm_struct *mm = current->mm;
 93         unsigned long gic_size, vvar_size, size, base, data_addr, vdso_addr, gic_pfn;
 94         struct vm_area_struct *vma;
 95         int ret;
 96 
 97         if (mmap_write_lock_killable(mm))
 98                 return -EINTR;
 99 
100         if (IS_ENABLED(CONFIG_MIPS_FP_SUPPORT)) {
101                 /* Map delay slot emulation page */
102                 base = mmap_region(NULL, STACK_TOP, PAGE_SIZE,
103                                 VM_READ | VM_EXEC |
104                                 VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
105                                 0, NULL);
106                 if (IS_ERR_VALUE(base)) {
107                         ret = base;
108                         goto out;
109                 }
110         }
111 
112         /*
113          * Determine total area size. This includes the VDSO data itself, the
114          * data page, and the GIC user page if present. Always create a mapping
115          * for the GIC user area if the GIC is present regardless of whether it
116          * is the current clocksource, in case it comes into use later on. We
117          * only map a page even though the total area is 64K, as we only need
118          * the counter registers at the start.
119          */
120         gic_size = mips_gic_present() ? PAGE_SIZE : 0;
121         vvar_size = gic_size + PAGE_SIZE;
122         size = vvar_size + image->size;
123 
124         /*
125          * Find a region that's large enough for us to perform the
126          * colour-matching alignment below.
127          */
128         if (cpu_has_dc_aliases)
129                 size += shm_align_mask + 1;
130 
131         base = get_unmapped_area(NULL, vdso_base(), size, 0, 0);
132         if (IS_ERR_VALUE(base)) {
133                 ret = base;
134                 goto out;
135         }
136 
137         /*
138          * If we suffer from dcache aliasing, ensure that the VDSO data page
139          * mapping is coloured the same as the kernel's mapping of that memory.
140          * This ensures that when the kernel updates the VDSO data userland
141          * will observe it without requiring cache invalidations.
142          */
143         if (cpu_has_dc_aliases) {
144                 base = __ALIGN_MASK(base, shm_align_mask);
145                 base += ((unsigned long)vdso_data - gic_size) & shm_align_mask;
146         }
147 
148         data_addr = base + gic_size;
149         vdso_addr = data_addr + PAGE_SIZE;
150 
151         vma = _install_special_mapping(mm, base, vvar_size,
152                                        VM_READ | VM_MAYREAD,
153                                        &vdso_vvar_mapping);
154         if (IS_ERR(vma)) {
155                 ret = PTR_ERR(vma);
156                 goto out;
157         }
158 
159         /* Map GIC user page. */
160         if (gic_size) {
161                 gic_pfn = virt_to_phys(mips_gic_base + MIPS_GIC_USER_OFS) >> PAGE_SHIFT;
162 
163                 ret = io_remap_pfn_range(vma, base, gic_pfn, gic_size,
164                                          pgprot_noncached(PAGE_READONLY));
165                 if (ret)
166                         goto out;
167         }
168 
169         /* Map data page. */
170         ret = remap_pfn_range(vma, data_addr,
171                               virt_to_phys(vdso_data) >> PAGE_SHIFT,
172                               PAGE_SIZE, PAGE_READONLY);
173         if (ret)
174                 goto out;
175 
176         /* Map VDSO image. */
177         vma = _install_special_mapping(mm, vdso_addr, image->size,
178                                        VM_READ | VM_EXEC |
179                                        VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
180                                        &image->mapping);
181         if (IS_ERR(vma)) {
182                 ret = PTR_ERR(vma);
183                 goto out;
184         }
185 
186         mm->context.vdso = (void *)vdso_addr;
187         ret = 0;
188 
189 out:
190         mmap_write_unlock(mm);
191         return ret;
192 }
193 

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