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Linux/arch/x86/mm/dump_pagetables.c

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  1 /*
  2  * Debug helper to dump the current kernel pagetables of the system
  3  * so that we can see what the various memory ranges are set to.
  4  *
  5  * (C) Copyright 2008 Intel Corporation
  6  *
  7  * Author: Arjan van de Ven <arjan@linux.intel.com>
  8  *
  9  * This program is free software; you can redistribute it and/or
 10  * modify it under the terms of the GNU General Public License
 11  * as published by the Free Software Foundation; version 2
 12  * of the License.
 13  */
 14 
 15 #include <linux/debugfs.h>
 16 #include <linux/mm.h>
 17 #include <linux/module.h>
 18 #include <linux/seq_file.h>
 19 
 20 #include <asm/pgtable.h>
 21 
 22 /*
 23  * The dumper groups pagetable entries of the same type into one, and for
 24  * that it needs to keep some state when walking, and flush this state
 25  * when a "break" in the continuity is found.
 26  */
 27 struct pg_state {
 28         int level;
 29         pgprot_t current_prot;
 30         unsigned long start_address;
 31         unsigned long current_address;
 32         const struct addr_marker *marker;
 33 };
 34 
 35 struct addr_marker {
 36         unsigned long start_address;
 37         const char *name;
 38 };
 39 
 40 /* indices for address_markers; keep sync'd w/ address_markers below */
 41 enum address_markers_idx {
 42         USER_SPACE_NR = 0,
 43 #ifdef CONFIG_X86_64
 44         KERNEL_SPACE_NR,
 45         LOW_KERNEL_NR,
 46         VMALLOC_START_NR,
 47         VMEMMAP_START_NR,
 48         HIGH_KERNEL_NR,
 49         MODULES_VADDR_NR,
 50         MODULES_END_NR,
 51 #else
 52         KERNEL_SPACE_NR,
 53         VMALLOC_START_NR,
 54         VMALLOC_END_NR,
 55 # ifdef CONFIG_HIGHMEM
 56         PKMAP_BASE_NR,
 57 # endif
 58         FIXADDR_START_NR,
 59 #endif
 60 };
 61 
 62 /* Address space markers hints */
 63 static struct addr_marker address_markers[] = {
 64         { 0, "User Space" },
 65 #ifdef CONFIG_X86_64
 66         { 0x8000000000000000UL, "Kernel Space" },
 67         { PAGE_OFFSET,          "Low Kernel Mapping" },
 68         { VMALLOC_START,        "vmalloc() Area" },
 69         { VMEMMAP_START,        "Vmemmap" },
 70         { __START_KERNEL_map,   "High Kernel Mapping" },
 71         { MODULES_VADDR,        "Modules" },
 72         { MODULES_END,          "End Modules" },
 73 #else
 74         { PAGE_OFFSET,          "Kernel Mapping" },
 75         { 0/* VMALLOC_START */, "vmalloc() Area" },
 76         { 0/*VMALLOC_END*/,     "vmalloc() End" },
 77 # ifdef CONFIG_HIGHMEM
 78         { 0/*PKMAP_BASE*/,      "Persisent kmap() Area" },
 79 # endif
 80         { 0/*FIXADDR_START*/,   "Fixmap Area" },
 81 #endif
 82         { -1, NULL }            /* End of list */
 83 };
 84 
 85 /* Multipliers for offsets within the PTEs */
 86 #define PTE_LEVEL_MULT (PAGE_SIZE)
 87 #define PMD_LEVEL_MULT (PTRS_PER_PTE * PTE_LEVEL_MULT)
 88 #define PUD_LEVEL_MULT (PTRS_PER_PMD * PMD_LEVEL_MULT)
 89 #define PGD_LEVEL_MULT (PTRS_PER_PUD * PUD_LEVEL_MULT)
 90 
 91 /*
 92  * Print a readable form of a pgprot_t to the seq_file
 93  */
 94 static void printk_prot(struct seq_file *m, pgprot_t prot, int level)
 95 {
 96         pgprotval_t pr = pgprot_val(prot);
 97         static const char * const level_name[] =
 98                 { "cr3", "pgd", "pud", "pmd", "pte" };
 99 
100         if (!pgprot_val(prot)) {
101                 /* Not present */
102                 seq_printf(m, "                          ");
103         } else {
104                 if (pr & _PAGE_USER)
105                         seq_printf(m, "USR ");
106                 else
107                         seq_printf(m, "    ");
108                 if (pr & _PAGE_RW)
109                         seq_printf(m, "RW ");
110                 else
111                         seq_printf(m, "ro ");
112                 if (pr & _PAGE_PWT)
113                         seq_printf(m, "PWT ");
114                 else
115                         seq_printf(m, "    ");
116                 if (pr & _PAGE_PCD)
117                         seq_printf(m, "PCD ");
118                 else
119                         seq_printf(m, "    ");
120 
121                 /* Bit 9 has a different meaning on level 3 vs 4 */
122                 if (level <= 3) {
123                         if (pr & _PAGE_PSE)
124                                 seq_printf(m, "PSE ");
125                         else
126                                 seq_printf(m, "    ");
127                 } else {
128                         if (pr & _PAGE_PAT)
129                                 seq_printf(m, "pat ");
130                         else
131                                 seq_printf(m, "    ");
132                 }
133                 if (pr & _PAGE_GLOBAL)
134                         seq_printf(m, "GLB ");
135                 else
136                         seq_printf(m, "    ");
137                 if (pr & _PAGE_NX)
138                         seq_printf(m, "NX ");
139                 else
140                         seq_printf(m, "x  ");
141         }
142         seq_printf(m, "%s\n", level_name[level]);
143 }
144 
145 /*
146  * On 64 bits, sign-extend the 48 bit address to 64 bit
147  */
148 static unsigned long normalize_addr(unsigned long u)
149 {
150 #ifdef CONFIG_X86_64
151         return (signed long)(u << 16) >> 16;
152 #else
153         return u;
154 #endif
155 }
156 
157 /*
158  * This function gets called on a break in a continuous series
159  * of PTE entries; the next one is different so we need to
160  * print what we collected so far.
161  */
162 static void note_page(struct seq_file *m, struct pg_state *st,
163                       pgprot_t new_prot, int level)
164 {
165         pgprotval_t prot, cur;
166         static const char units[] = "KMGTPE";
167 
168         /*
169          * If we have a "break" in the series, we need to flush the state that
170          * we have now. "break" is either changing perms, levels or
171          * address space marker.
172          */
173         prot = pgprot_val(new_prot) & PTE_FLAGS_MASK;
174         cur = pgprot_val(st->current_prot) & PTE_FLAGS_MASK;
175 
176         if (!st->level) {
177                 /* First entry */
178                 st->current_prot = new_prot;
179                 st->level = level;
180                 st->marker = address_markers;
181                 seq_printf(m, "---[ %s ]---\n", st->marker->name);
182         } else if (prot != cur || level != st->level ||
183                    st->current_address >= st->marker[1].start_address) {
184                 const char *unit = units;
185                 unsigned long delta;
186                 int width = sizeof(unsigned long) * 2;
187 
188                 /*
189                  * Now print the actual finished series
190                  */
191                 seq_printf(m, "0x%0*lx-0x%0*lx   ",
192                            width, st->start_address,
193                            width, st->current_address);
194 
195                 delta = (st->current_address - st->start_address) >> 10;
196                 while (!(delta & 1023) && unit[1]) {
197                         delta >>= 10;
198                         unit++;
199                 }
200                 seq_printf(m, "%9lu%c ", delta, *unit);
201                 printk_prot(m, st->current_prot, st->level);
202 
203                 /*
204                  * We print markers for special areas of address space,
205                  * such as the start of vmalloc space etc.
206                  * This helps in the interpretation.
207                  */
208                 if (st->current_address >= st->marker[1].start_address) {
209                         st->marker++;
210                         seq_printf(m, "---[ %s ]---\n", st->marker->name);
211                 }
212 
213                 st->start_address = st->current_address;
214                 st->current_prot = new_prot;
215                 st->level = level;
216         }
217 }
218 
219 static void walk_pte_level(struct seq_file *m, struct pg_state *st, pmd_t addr,
220                                                         unsigned long P)
221 {
222         int i;
223         pte_t *start;
224 
225         start = (pte_t *) pmd_page_vaddr(addr);
226         for (i = 0; i < PTRS_PER_PTE; i++) {
227                 pgprot_t prot = pte_pgprot(*start);
228 
229                 st->current_address = normalize_addr(P + i * PTE_LEVEL_MULT);
230                 note_page(m, st, prot, 4);
231                 start++;
232         }
233 }
234 
235 #if PTRS_PER_PMD > 1
236 
237 static void walk_pmd_level(struct seq_file *m, struct pg_state *st, pud_t addr,
238                                                         unsigned long P)
239 {
240         int i;
241         pmd_t *start;
242 
243         start = (pmd_t *) pud_page_vaddr(addr);
244         for (i = 0; i < PTRS_PER_PMD; i++) {
245                 st->current_address = normalize_addr(P + i * PMD_LEVEL_MULT);
246                 if (!pmd_none(*start)) {
247                         pgprotval_t prot = pmd_val(*start) & PTE_FLAGS_MASK;
248 
249                         if (pmd_large(*start) || !pmd_present(*start))
250                                 note_page(m, st, __pgprot(prot), 3);
251                         else
252                                 walk_pte_level(m, st, *start,
253                                                P + i * PMD_LEVEL_MULT);
254                 } else
255                         note_page(m, st, __pgprot(0), 3);
256                 start++;
257         }
258 }
259 
260 #else
261 #define walk_pmd_level(m,s,a,p) walk_pte_level(m,s,__pmd(pud_val(a)),p)
262 #define pud_large(a) pmd_large(__pmd(pud_val(a)))
263 #define pud_none(a)  pmd_none(__pmd(pud_val(a)))
264 #endif
265 
266 #if PTRS_PER_PUD > 1
267 
268 static void walk_pud_level(struct seq_file *m, struct pg_state *st, pgd_t addr,
269                                                         unsigned long P)
270 {
271         int i;
272         pud_t *start;
273 
274         start = (pud_t *) pgd_page_vaddr(addr);
275 
276         for (i = 0; i < PTRS_PER_PUD; i++) {
277                 st->current_address = normalize_addr(P + i * PUD_LEVEL_MULT);
278                 if (!pud_none(*start)) {
279                         pgprotval_t prot = pud_val(*start) & PTE_FLAGS_MASK;
280 
281                         if (pud_large(*start) || !pud_present(*start))
282                                 note_page(m, st, __pgprot(prot), 2);
283                         else
284                                 walk_pmd_level(m, st, *start,
285                                                P + i * PUD_LEVEL_MULT);
286                 } else
287                         note_page(m, st, __pgprot(0), 2);
288 
289                 start++;
290         }
291 }
292 
293 #else
294 #define walk_pud_level(m,s,a,p) walk_pmd_level(m,s,__pud(pgd_val(a)),p)
295 #define pgd_large(a) pud_large(__pud(pgd_val(a)))
296 #define pgd_none(a)  pud_none(__pud(pgd_val(a)))
297 #endif
298 
299 static void walk_pgd_level(struct seq_file *m)
300 {
301 #ifdef CONFIG_X86_64
302         pgd_t *start = (pgd_t *) &init_level4_pgt;
303 #else
304         pgd_t *start = swapper_pg_dir;
305 #endif
306         int i;
307         struct pg_state st;
308 
309         memset(&st, 0, sizeof(st));
310 
311         for (i = 0; i < PTRS_PER_PGD; i++) {
312                 st.current_address = normalize_addr(i * PGD_LEVEL_MULT);
313                 if (!pgd_none(*start)) {
314                         pgprotval_t prot = pgd_val(*start) & PTE_FLAGS_MASK;
315 
316                         if (pgd_large(*start) || !pgd_present(*start))
317                                 note_page(m, &st, __pgprot(prot), 1);
318                         else
319                                 walk_pud_level(m, &st, *start,
320                                                i * PGD_LEVEL_MULT);
321                 } else
322                         note_page(m, &st, __pgprot(0), 1);
323 
324                 start++;
325         }
326 
327         /* Flush out the last page */
328         st.current_address = normalize_addr(PTRS_PER_PGD*PGD_LEVEL_MULT);
329         note_page(m, &st, __pgprot(0), 0);
330 }
331 
332 static int ptdump_show(struct seq_file *m, void *v)
333 {
334         walk_pgd_level(m);
335         return 0;
336 }
337 
338 static int ptdump_open(struct inode *inode, struct file *filp)
339 {
340         return single_open(filp, ptdump_show, NULL);
341 }
342 
343 static const struct file_operations ptdump_fops = {
344         .open           = ptdump_open,
345         .read           = seq_read,
346         .llseek         = seq_lseek,
347         .release        = single_release,
348 };
349 
350 static int pt_dump_init(void)
351 {
352         struct dentry *pe;
353 
354 #ifdef CONFIG_X86_32
355         /* Not a compile-time constant on x86-32 */
356         address_markers[VMALLOC_START_NR].start_address = VMALLOC_START;
357         address_markers[VMALLOC_END_NR].start_address = VMALLOC_END;
358 # ifdef CONFIG_HIGHMEM
359         address_markers[PKMAP_BASE_NR].start_address = PKMAP_BASE;
360 # endif
361         address_markers[FIXADDR_START_NR].start_address = FIXADDR_START;
362 #endif
363 
364         pe = debugfs_create_file("kernel_page_tables", 0600, NULL, NULL,
365                                  &ptdump_fops);
366         if (!pe)
367                 return -ENOMEM;
368 
369         return 0;
370 }
371 
372 __initcall(pt_dump_init);
373 MODULE_LICENSE("GPL");
374 MODULE_AUTHOR("Arjan van de Ven <arjan@linux.intel.com>");
375 MODULE_DESCRIPTION("Kernel debugging helper that dumps pagetables");
376 

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