xref: /openbmc/linux/arch/mips/kernel/vdso.c (revision 8032bf12)
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 
init_vdso_image(struct mips_vdso_image * image)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 
init_vdso(void)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 
vdso_base(void)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_u32_below(VDSO_RANDOMIZE_SIZE);
83 		base = PAGE_ALIGN(base);
84 	}
85 
86 	return base;
87 }
88 
arch_setup_additional_pages(struct linux_binprm * bprm,int uses_interp)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, gic_base;
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_base = (unsigned long)mips_gic_base + MIPS_GIC_USER_OFS;
162 		gic_pfn = PFN_DOWN(__pa(gic_base));
163 
164 		ret = io_remap_pfn_range(vma, base, gic_pfn, gic_size,
165 					 pgprot_noncached(vma->vm_page_prot));
166 		if (ret)
167 			goto out;
168 	}
169 
170 	/* Map data page. */
171 	ret = remap_pfn_range(vma, data_addr,
172 			      virt_to_phys(vdso_data) >> PAGE_SHIFT,
173 			      PAGE_SIZE, vma->vm_page_prot);
174 	if (ret)
175 		goto out;
176 
177 	/* Map VDSO image. */
178 	vma = _install_special_mapping(mm, vdso_addr, image->size,
179 				       VM_READ | VM_EXEC |
180 				       VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
181 				       &image->mapping);
182 	if (IS_ERR(vma)) {
183 		ret = PTR_ERR(vma);
184 		goto out;
185 	}
186 
187 	mm->context.vdso = (void *)vdso_addr;
188 	ret = 0;
189 
190 out:
191 	mmap_write_unlock(mm);
192 	return ret;
193 }
194