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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;
 75 
 76         /* Skip the delay slot emulation page */
 77         base = STACK_TOP + PAGE_SIZE;
 78 
 79         if (current->flags & PF_RANDOMIZE) {
 80                 base += get_random_int() & (VDSO_RANDOMIZE_SIZE - 1);
 81                 base = PAGE_ALIGN(base);
 82         }
 83 
 84         return base;
 85 }
 86 
 87 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 88 {
 89         struct mips_vdso_image *image = current->thread.abi->vdso;
 90         struct mm_struct *mm = current->mm;
 91         unsigned long gic_size, vvar_size, size, base, data_addr, vdso_addr, gic_pfn;
 92         struct vm_area_struct *vma;
 93         int ret;
 94 
 95         if (down_write_killable(&mm->mmap_sem))
 96                 return -EINTR;
 97 
 98         /* Map delay slot emulation page */
 99         base = mmap_region(NULL, STACK_TOP, PAGE_SIZE,
100                            VM_READ | VM_EXEC |
101                            VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
102                            0, NULL);
103         if (IS_ERR_VALUE(base)) {
104                 ret = base;
105                 goto out;
106         }
107 
108         /*
109          * Determine total area size. This includes the VDSO data itself, the
110          * data page, and the GIC user page if present. Always create a mapping
111          * for the GIC user area if the GIC is present regardless of whether it
112          * is the current clocksource, in case it comes into use later on. We
113          * only map a page even though the total area is 64K, as we only need
114          * the counter registers at the start.
115          */
116         gic_size = mips_gic_present() ? PAGE_SIZE : 0;
117         vvar_size = gic_size + PAGE_SIZE;
118         size = vvar_size + image->size;
119 
120         /*
121          * Find a region that's large enough for us to perform the
122          * colour-matching alignment below.
123          */
124         if (cpu_has_dc_aliases)
125                 size += shm_align_mask + 1;
126 
127         base = get_unmapped_area(NULL, vdso_base(), size, 0, 0);
128         if (IS_ERR_VALUE(base)) {
129                 ret = base;
130                 goto out;
131         }
132 
133         /*
134          * If we suffer from dcache aliasing, ensure that the VDSO data page
135          * mapping is coloured the same as the kernel's mapping of that memory.
136          * This ensures that when the kernel updates the VDSO data userland
137          * will observe it without requiring cache invalidations.
138          */
139         if (cpu_has_dc_aliases) {
140                 base = __ALIGN_MASK(base, shm_align_mask);
141                 base += ((unsigned long)vdso_data - gic_size) & shm_align_mask;
142         }
143 
144         data_addr = base + gic_size;
145         vdso_addr = data_addr + PAGE_SIZE;
146 
147         vma = _install_special_mapping(mm, base, vvar_size,
148                                        VM_READ | VM_MAYREAD,
149                                        &vdso_vvar_mapping);
150         if (IS_ERR(vma)) {
151                 ret = PTR_ERR(vma);
152                 goto out;
153         }
154 
155         /* Map GIC user page. */
156         if (gic_size) {
157                 gic_pfn = virt_to_phys(mips_gic_base + MIPS_GIC_USER_OFS) >> PAGE_SHIFT;
158 
159                 ret = io_remap_pfn_range(vma, base, gic_pfn, gic_size,
160                                          pgprot_noncached(PAGE_READONLY));
161                 if (ret)
162                         goto out;
163         }
164 
165         /* Map data page. */
166         ret = remap_pfn_range(vma, data_addr,
167                               virt_to_phys(vdso_data) >> PAGE_SHIFT,
168                               PAGE_SIZE, PAGE_READONLY);
169         if (ret)
170                 goto out;
171 
172         /* Map VDSO image. */
173         vma = _install_special_mapping(mm, vdso_addr, image->size,
174                                        VM_READ | VM_EXEC |
175                                        VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
176                                        &image->mapping);
177         if (IS_ERR(vma)) {
178                 ret = PTR_ERR(vma);
179                 goto out;
180         }
181 
182         mm->context.vdso = (void *)vdso_addr;
183         ret = 0;
184 
185 out:
186         up_write(&mm->mmap_sem);
187         return ret;
188 }
189 

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