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Linux/arch/um/kernel/skas/mmu.c

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  1 /*
  2  * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
  3  * Licensed under the GPL
  4  */
  5 
  6 #include "linux/mm.h"
  7 #include "linux/sched.h"
  8 #include "asm/pgalloc.h"
  9 #include "asm/pgtable.h"
 10 #include "as-layout.h"
 11 #include "os.h"
 12 #include "skas.h"
 13 
 14 extern int __syscall_stub_start;
 15 
 16 static int init_stub_pte(struct mm_struct *mm, unsigned long proc,
 17                          unsigned long kernel)
 18 {
 19         pgd_t *pgd;
 20         pud_t *pud;
 21         pmd_t *pmd;
 22         pte_t *pte;
 23 
 24         pgd = pgd_offset(mm, proc);
 25         pud = pud_alloc(mm, pgd, proc);
 26         if (!pud)
 27                 goto out;
 28 
 29         pmd = pmd_alloc(mm, pud, proc);
 30         if (!pmd)
 31                 goto out_pmd;
 32 
 33         pte = pte_alloc_map(mm, pmd, proc);
 34         if (!pte)
 35                 goto out_pte;
 36 
 37         *pte = mk_pte(virt_to_page(kernel), __pgprot(_PAGE_PRESENT));
 38         *pte = pte_mkread(*pte);
 39         return 0;
 40 
 41  out_pte:
 42         pmd_free(mm, pmd);
 43  out_pmd:
 44         pud_free(mm, pud);
 45  out:
 46         return -ENOMEM;
 47 }
 48 
 49 int init_new_context(struct task_struct *task, struct mm_struct *mm)
 50 {
 51         struct mm_context *from_mm = NULL;
 52         struct mm_context *to_mm = &mm->context;
 53         unsigned long stack = 0;
 54         int ret = -ENOMEM;
 55 
 56         if (skas_needs_stub) {
 57                 stack = get_zeroed_page(GFP_KERNEL);
 58                 if (stack == 0)
 59                         goto out;
 60         }
 61 
 62         to_mm->id.stack = stack;
 63         if (current->mm != NULL && current->mm != &init_mm)
 64                 from_mm = &current->mm->context;
 65 
 66         if (proc_mm) {
 67                 ret = new_mm(stack);
 68                 if (ret < 0) {
 69                         printk(KERN_ERR "init_new_context_skas - "
 70                                "new_mm failed, errno = %d\n", ret);
 71                         goto out_free;
 72                 }
 73                 to_mm->id.u.mm_fd = ret;
 74         }
 75         else {
 76                 if (from_mm)
 77                         to_mm->id.u.pid = copy_context_skas0(stack,
 78                                                              from_mm->id.u.pid);
 79                 else to_mm->id.u.pid = start_userspace(stack);
 80 
 81                 if (to_mm->id.u.pid < 0) {
 82                         ret = to_mm->id.u.pid;
 83                         goto out_free;
 84                 }
 85         }
 86 
 87         ret = init_new_ldt(to_mm, from_mm);
 88         if (ret < 0) {
 89                 printk(KERN_ERR "init_new_context_skas - init_ldt"
 90                        " failed, errno = %d\n", ret);
 91                 goto out_free;
 92         }
 93 
 94         to_mm->stub_pages = NULL;
 95 
 96         return 0;
 97 
 98  out_free:
 99         if (to_mm->id.stack != 0)
100                 free_page(to_mm->id.stack);
101  out:
102         return ret;
103 }
104 
105 void arch_dup_mmap(struct mm_struct *oldmm, struct mm_struct *mm)
106 {
107         struct page **pages;
108         int err, ret;
109 
110         if (!skas_needs_stub)
111                 return;
112 
113         ret = init_stub_pte(mm, STUB_CODE,
114                             (unsigned long) &__syscall_stub_start);
115         if (ret)
116                 goto out;
117 
118         ret = init_stub_pte(mm, STUB_DATA, mm->context.id.stack);
119         if (ret)
120                 goto out;
121 
122         pages = kmalloc(2 * sizeof(struct page *), GFP_KERNEL);
123         if (pages == NULL) {
124                 printk(KERN_ERR "arch_dup_mmap failed to allocate 2 page "
125                        "pointers\n");
126                 goto out;
127         }
128 
129         pages[0] = virt_to_page(&__syscall_stub_start);
130         pages[1] = virt_to_page(mm->context.id.stack);
131         mm->context.stub_pages = pages;
132 
133         /* dup_mmap already holds mmap_sem */
134         err = install_special_mapping(mm, STUB_START, STUB_END - STUB_START,
135                                       VM_READ | VM_MAYREAD | VM_EXEC |
136                                       VM_MAYEXEC | VM_DONTCOPY, pages);
137         if (err) {
138                 printk(KERN_ERR "install_special_mapping returned %d\n", err);
139                 goto out_free;
140         }
141         return;
142 
143 out_free:
144         kfree(pages);
145 out:
146         force_sigsegv(SIGSEGV, current);
147 }
148 
149 void arch_exit_mmap(struct mm_struct *mm)
150 {
151         pte_t *pte;
152 
153         if (mm->context.stub_pages != NULL)
154                 kfree(mm->context.stub_pages);
155         pte = virt_to_pte(mm, STUB_CODE);
156         if (pte != NULL)
157                 pte_clear(mm, STUB_CODE, pte);
158 
159         pte = virt_to_pte(mm, STUB_DATA);
160         if (pte == NULL)
161                 return;
162 
163         pte_clear(mm, STUB_DATA, pte);
164 }
165 
166 void destroy_context(struct mm_struct *mm)
167 {
168         struct mm_context *mmu = &mm->context;
169 
170         if (proc_mm)
171                 os_close_file(mmu->id.u.mm_fd);
172         else {
173                 /*
174                  * If init_new_context wasn't called, this will be
175                  * zero, resulting in a kill(0), which will result in the
176                  * whole UML suddenly dying.  Also, cover negative and
177                  * 1 cases, since they shouldn't happen either.
178                  */
179                 if (mmu->id.u.pid < 2) {
180                         printk(KERN_ERR "corrupt mm_context - pid = %d\n",
181                                mmu->id.u.pid);
182                         return;
183                 }
184                 os_kill_ptraced_process(mmu->id.u.pid, 1);
185         }
186 
187         if (skas_needs_stub)
188                 free_page(mmu->id.stack);
189 
190         free_ldt(mmu);
191 }
192 

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