[PATCH] x86/x86_64: mark rodata section read only: generic x86-64 bugfix
[linux-2.6.git] / arch / x86_64 / mm / pageattr.c
1 /* 
2  * Copyright 2002 Andi Kleen, SuSE Labs. 
3  * Thanks to Ben LaHaise for precious feedback.
4  */ 
5
6 #include <linux/config.h>
7 #include <linux/mm.h>
8 #include <linux/sched.h>
9 #include <linux/highmem.h>
10 #include <linux/module.h>
11 #include <linux/slab.h>
12 #include <asm/uaccess.h>
13 #include <asm/processor.h>
14 #include <asm/tlbflush.h>
15 #include <asm/io.h>
16
17 static inline pte_t *lookup_address(unsigned long address) 
18
19         pgd_t *pgd = pgd_offset_k(address);
20         pud_t *pud;
21         pmd_t *pmd;
22         pte_t *pte;
23         if (pgd_none(*pgd))
24                 return NULL;
25         pud = pud_offset(pgd, address);
26         if (!pud_present(*pud))
27                 return NULL; 
28         pmd = pmd_offset(pud, address);
29         if (!pmd_present(*pmd))
30                 return NULL; 
31         if (pmd_large(*pmd))
32                 return (pte_t *)pmd;
33         pte = pte_offset_kernel(pmd, address);
34         if (pte && !pte_present(*pte))
35                 pte = NULL; 
36         return pte;
37
38
39 static struct page *split_large_page(unsigned long address, pgprot_t prot,
40                                      pgprot_t ref_prot)
41
42         int i; 
43         unsigned long addr;
44         struct page *base = alloc_pages(GFP_KERNEL, 0);
45         pte_t *pbase;
46         if (!base) 
47                 return NULL;
48         address = __pa(address);
49         addr = address & LARGE_PAGE_MASK; 
50         pbase = (pte_t *)page_address(base);
51         for (i = 0; i < PTRS_PER_PTE; i++, addr += PAGE_SIZE) {
52                 pbase[i] = pfn_pte(addr >> PAGE_SHIFT, 
53                                    addr == address ? prot : ref_prot);
54         }
55         return base;
56
57
58
59 static void flush_kernel_map(void *address) 
60 {
61         if (0 && address && cpu_has_clflush) {
62                 /* is this worth it? */ 
63                 int i;
64                 for (i = 0; i < PAGE_SIZE; i += boot_cpu_data.x86_clflush_size) 
65                         asm volatile("clflush (%0)" :: "r" (address + i)); 
66         } else
67                 asm volatile("wbinvd":::"memory"); 
68         if (address)
69                 __flush_tlb_one(address);
70         else
71                 __flush_tlb_all();
72 }
73
74
75 static inline void flush_map(unsigned long address)
76 {       
77         on_each_cpu(flush_kernel_map, (void *)address, 1, 1);
78 }
79
80 struct deferred_page { 
81         struct deferred_page *next; 
82         struct page *fpage;
83         unsigned long address;
84 }; 
85 static struct deferred_page *df_list; /* protected by init_mm.mmap_sem */
86
87 static inline void save_page(unsigned long address, struct page *fpage)
88 {
89         struct deferred_page *df;
90         df = kmalloc(sizeof(struct deferred_page), GFP_KERNEL); 
91         if (!df) {
92                 flush_map(address);
93                 __free_page(fpage);
94         } else { 
95                 df->next = df_list;
96                 df->fpage = fpage;
97                 df->address = address;
98                 df_list = df;
99         }                       
100 }
101
102 /* 
103  * No more special protections in this 2/4MB area - revert to a
104  * large page again. 
105  */
106 static void revert_page(unsigned long address, pgprot_t ref_prot)
107 {
108         pgd_t *pgd;
109         pud_t *pud;
110         pmd_t *pmd;
111         pte_t large_pte;
112
113         pgd = pgd_offset_k(address);
114         BUG_ON(pgd_none(*pgd));
115         pud = pud_offset(pgd,address);
116         BUG_ON(pud_none(*pud));
117         pmd = pmd_offset(pud, address);
118         BUG_ON(pmd_val(*pmd) & _PAGE_PSE);
119         pgprot_val(ref_prot) |= _PAGE_PSE;
120         large_pte = mk_pte_phys(__pa(address) & LARGE_PAGE_MASK, ref_prot);
121         set_pte((pte_t *)pmd, large_pte);
122 }      
123
124 static int
125 __change_page_attr(unsigned long address, unsigned long pfn, pgprot_t prot,
126                                    pgprot_t ref_prot)
127
128         pte_t *kpte; 
129         struct page *kpte_page;
130         unsigned kpte_flags;
131         pgprot_t ref_prot2;
132         kpte = lookup_address(address);
133         if (!kpte) return 0;
134         kpte_page = virt_to_page(((unsigned long)kpte) & PAGE_MASK);
135         kpte_flags = pte_val(*kpte); 
136         if (pgprot_val(prot) != pgprot_val(ref_prot)) { 
137                 if ((kpte_flags & _PAGE_PSE) == 0) { 
138                         set_pte(kpte, pfn_pte(pfn, prot));
139                 } else {
140                         /*
141                          * split_large_page will take the reference for this change_page_attr
142                          * on the split page.
143                          */
144
145                         struct page *split;
146                         ref_prot2 = __pgprot(pgprot_val(pte_pgprot(*lookup_address(address))) & ~(1<<_PAGE_BIT_PSE));
147
148                         split = split_large_page(address, prot, ref_prot2);
149                         if (!split)
150                                 return -ENOMEM;
151                         set_pte(kpte,mk_pte(split, ref_prot2));
152                         kpte_page = split;
153                 }       
154                 get_page(kpte_page);
155         } else if ((kpte_flags & _PAGE_PSE) == 0) { 
156                 set_pte(kpte, pfn_pte(pfn, ref_prot));
157                 __put_page(kpte_page);
158         } else
159                 BUG();
160
161         /* on x86-64 the direct mapping set at boot is not using 4k pages */
162         BUG_ON(PageReserved(kpte_page));
163
164         switch (page_count(kpte_page)) {
165         case 1:
166                 save_page(address, kpte_page);               
167                 revert_page(address, ref_prot);
168                 break;
169         case 0:
170                 BUG(); /* memleak and failed 2M page regeneration */
171         }
172         return 0;
173
174
175 /*
176  * Change the page attributes of an page in the linear mapping.
177  *
178  * This should be used when a page is mapped with a different caching policy
179  * than write-back somewhere - some CPUs do not like it when mappings with
180  * different caching policies exist. This changes the page attributes of the
181  * in kernel linear mapping too.
182  * 
183  * The caller needs to ensure that there are no conflicting mappings elsewhere.
184  * This function only deals with the kernel linear map.
185  * 
186  * Caller must call global_flush_tlb() after this.
187  */
188 int change_page_attr_addr(unsigned long address, int numpages, pgprot_t prot)
189 {
190         int err = 0; 
191         int i; 
192
193         down_write(&init_mm.mmap_sem);
194         for (i = 0; i < numpages; i++, address += PAGE_SIZE) {
195                 unsigned long pfn = __pa(address) >> PAGE_SHIFT;
196
197                 err = __change_page_attr(address, pfn, prot, PAGE_KERNEL);
198                 if (err) 
199                         break; 
200                 /* Handle kernel mapping too which aliases part of the
201                  * lowmem */
202                 if (__pa(address) < KERNEL_TEXT_SIZE) {
203                         unsigned long addr2;
204                         pgprot_t prot2 = prot;
205                         addr2 = __START_KERNEL_map + __pa(address);
206                         pgprot_val(prot2) &= ~_PAGE_NX;
207                         err = __change_page_attr(addr2, pfn, prot2, PAGE_KERNEL_EXEC);
208                 } 
209         }       
210         up_write(&init_mm.mmap_sem); 
211         return err;
212 }
213
214 /* Don't call this for MMIO areas that may not have a mem_map entry */
215 int change_page_attr(struct page *page, int numpages, pgprot_t prot)
216 {
217         unsigned long addr = (unsigned long)page_address(page);
218         return change_page_attr_addr(addr, numpages, prot);
219 }
220
221 void global_flush_tlb(void)
222
223         struct deferred_page *df, *next_df;
224
225         down_read(&init_mm.mmap_sem);
226         df = xchg(&df_list, NULL);
227         up_read(&init_mm.mmap_sem);
228         flush_map((df && !df->next) ? df->address : 0);
229         for (; df; df = next_df) { 
230                 next_df = df->next;
231                 if (df->fpage) 
232                         __free_page(df->fpage);
233                 kfree(df);
234         } 
235
236
237 EXPORT_SYMBOL(change_page_attr);
238 EXPORT_SYMBOL(global_flush_tlb);