1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Copyright 2016, Rashmica Gupta, IBM Corp. 4 * 5 * This traverses the kernel pagetables and dumps the 6 * information about the used sections of memory to 7 * /sys/kernel/debug/kernel_pagetables. 8 * 9 * Derived from the arm64 implementation: 10 * Copyright (c) 2014, The Linux Foundation, Laura Abbott. 11 * (C) Copyright 2008 Intel Corporation, Arjan van de Ven. 12 */ 13 #include <linux/debugfs.h> 14 #include <linux/fs.h> 15 #include <linux/hugetlb.h> 16 #include <linux/io.h> 17 #include <linux/mm.h> 18 #include <linux/highmem.h> 19 #include <linux/sched.h> 20 #include <linux/seq_file.h> 21 #include <asm/fixmap.h> 22 #include <linux/const.h> 23 #include <asm/page.h> 24 #include <asm/hugetlb.h> 25 26 #include <mm/mmu_decl.h> 27 28 #include "ptdump.h" 29 30 /* 31 * To visualise what is happening, 32 * 33 * - PTRS_PER_P** = how many entries there are in the corresponding P** 34 * - P**_SHIFT = how many bits of the address we use to index into the 35 * corresponding P** 36 * - P**_SIZE is how much memory we can access through the table - not the 37 * size of the table itself. 38 * P**={PGD, PUD, PMD, PTE} 39 * 40 * 41 * Each entry of the PGD points to a PUD. Each entry of a PUD points to a 42 * PMD. Each entry of a PMD points to a PTE. And every PTE entry points to 43 * a page. 44 * 45 * In the case where there are only 3 levels, the PUD is folded into the 46 * PGD: every PUD has only one entry which points to the PMD. 47 * 48 * The page dumper groups page table entries of the same type into a single 49 * description. It uses pg_state to track the range information while 50 * iterating over the PTE entries. When the continuity is broken it then 51 * dumps out a description of the range - ie PTEs that are virtually contiguous 52 * with the same PTE flags are chunked together. This is to make it clear how 53 * different areas of the kernel virtual memory are used. 54 * 55 */ 56 struct pg_state { 57 struct seq_file *seq; 58 const struct addr_marker *marker; 59 unsigned long start_address; 60 unsigned long start_pa; 61 unsigned long last_pa; 62 unsigned long page_size; 63 unsigned int level; 64 u64 current_flags; 65 bool check_wx; 66 unsigned long wx_pages; 67 }; 68 69 struct addr_marker { 70 unsigned long start_address; 71 const char *name; 72 }; 73 74 static struct addr_marker address_markers[] = { 75 { 0, "Start of kernel VM" }, 76 #ifdef MODULES_VADDR 77 { 0, "modules start" }, 78 { 0, "modules end" }, 79 #endif 80 { 0, "vmalloc() Area" }, 81 { 0, "vmalloc() End" }, 82 #ifdef CONFIG_PPC64 83 { 0, "isa I/O start" }, 84 { 0, "isa I/O end" }, 85 { 0, "phb I/O start" }, 86 { 0, "phb I/O end" }, 87 { 0, "I/O remap start" }, 88 { 0, "I/O remap end" }, 89 { 0, "vmemmap start" }, 90 #else 91 { 0, "Early I/O remap start" }, 92 { 0, "Early I/O remap end" }, 93 #ifdef CONFIG_HIGHMEM 94 { 0, "Highmem PTEs start" }, 95 { 0, "Highmem PTEs end" }, 96 #endif 97 { 0, "Fixmap start" }, 98 { 0, "Fixmap end" }, 99 #endif 100 #ifdef CONFIG_KASAN 101 { 0, "kasan shadow mem start" }, 102 { 0, "kasan shadow mem end" }, 103 #endif 104 { -1, NULL }, 105 }; 106 107 #define pt_dump_seq_printf(m, fmt, args...) \ 108 ({ \ 109 if (m) \ 110 seq_printf(m, fmt, ##args); \ 111 }) 112 113 #define pt_dump_seq_putc(m, c) \ 114 ({ \ 115 if (m) \ 116 seq_putc(m, c); \ 117 }) 118 119 void pt_dump_size(struct seq_file *m, unsigned long size) 120 { 121 static const char units[] = "KMGTPE"; 122 const char *unit = units; 123 124 /* Work out what appropriate unit to use */ 125 while (!(size & 1023) && unit[1]) { 126 size >>= 10; 127 unit++; 128 } 129 pt_dump_seq_printf(m, "%9lu%c ", size, *unit); 130 } 131 132 static void dump_flag_info(struct pg_state *st, const struct flag_info 133 *flag, u64 pte, int num) 134 { 135 unsigned int i; 136 137 for (i = 0; i < num; i++, flag++) { 138 const char *s = NULL; 139 u64 val; 140 141 /* flag not defined so don't check it */ 142 if (flag->mask == 0) 143 continue; 144 /* Some 'flags' are actually values */ 145 if (flag->is_val) { 146 val = pte & flag->val; 147 if (flag->shift) 148 val = val >> flag->shift; 149 pt_dump_seq_printf(st->seq, " %s:%llx", flag->set, val); 150 } else { 151 if ((pte & flag->mask) == flag->val) 152 s = flag->set; 153 else 154 s = flag->clear; 155 if (s) 156 pt_dump_seq_printf(st->seq, " %s", s); 157 } 158 st->current_flags &= ~flag->mask; 159 } 160 if (st->current_flags != 0) 161 pt_dump_seq_printf(st->seq, " unknown flags:%llx", st->current_flags); 162 } 163 164 static void dump_addr(struct pg_state *st, unsigned long addr) 165 { 166 unsigned long delta; 167 168 #ifdef CONFIG_PPC64 169 #define REG "0x%016lx" 170 #else 171 #define REG "0x%08lx" 172 #endif 173 174 pt_dump_seq_printf(st->seq, REG "-" REG " ", st->start_address, addr - 1); 175 if (st->start_pa == st->last_pa && st->start_address + st->page_size != addr) { 176 pt_dump_seq_printf(st->seq, "[" REG "]", st->start_pa); 177 delta = st->page_size >> 10; 178 } else { 179 pt_dump_seq_printf(st->seq, " " REG " ", st->start_pa); 180 delta = (addr - st->start_address) >> 10; 181 } 182 pt_dump_size(st->seq, delta); 183 } 184 185 static void note_prot_wx(struct pg_state *st, unsigned long addr) 186 { 187 pte_t pte = __pte(st->current_flags); 188 189 if (!IS_ENABLED(CONFIG_PPC_DEBUG_WX) || !st->check_wx) 190 return; 191 192 if (!pte_write(pte) || !pte_exec(pte)) 193 return; 194 195 WARN_ONCE(1, "powerpc/mm: Found insecure W+X mapping at address %p/%pS\n", 196 (void *)st->start_address, (void *)st->start_address); 197 198 st->wx_pages += (addr - st->start_address) / PAGE_SIZE; 199 } 200 201 static void note_page_update_state(struct pg_state *st, unsigned long addr, 202 unsigned int level, u64 val, unsigned long page_size) 203 { 204 u64 flag = val & pg_level[level].mask; 205 u64 pa = val & PTE_RPN_MASK; 206 207 st->level = level; 208 st->current_flags = flag; 209 st->start_address = addr; 210 st->start_pa = pa; 211 st->page_size = page_size; 212 213 while (addr >= st->marker[1].start_address) { 214 st->marker++; 215 pt_dump_seq_printf(st->seq, "---[ %s ]---\n", st->marker->name); 216 } 217 } 218 219 static void note_page(struct pg_state *st, unsigned long addr, 220 unsigned int level, u64 val, unsigned long page_size) 221 { 222 u64 flag = val & pg_level[level].mask; 223 u64 pa = val & PTE_RPN_MASK; 224 225 /* At first no level is set */ 226 if (!st->level) { 227 pt_dump_seq_printf(st->seq, "---[ %s ]---\n", st->marker->name); 228 note_page_update_state(st, addr, level, val, page_size); 229 /* 230 * Dump the section of virtual memory when: 231 * - the PTE flags from one entry to the next differs. 232 * - we change levels in the tree. 233 * - the address is in a different section of memory and is thus 234 * used for a different purpose, regardless of the flags. 235 * - the pa of this page is not adjacent to the last inspected page 236 */ 237 } else if (flag != st->current_flags || level != st->level || 238 addr >= st->marker[1].start_address || 239 (pa != st->last_pa + st->page_size && 240 (pa != st->start_pa || st->start_pa != st->last_pa))) { 241 242 /* Check the PTE flags */ 243 if (st->current_flags) { 244 note_prot_wx(st, addr); 245 dump_addr(st, addr); 246 247 /* Dump all the flags */ 248 if (pg_level[st->level].flag) 249 dump_flag_info(st, pg_level[st->level].flag, 250 st->current_flags, 251 pg_level[st->level].num); 252 253 pt_dump_seq_putc(st->seq, '\n'); 254 } 255 256 /* 257 * Address indicates we have passed the end of the 258 * current section of virtual memory 259 */ 260 note_page_update_state(st, addr, level, val, page_size); 261 } 262 st->last_pa = pa; 263 } 264 265 static void walk_pte(struct pg_state *st, pmd_t *pmd, unsigned long start) 266 { 267 pte_t *pte = pte_offset_kernel(pmd, 0); 268 unsigned long addr; 269 unsigned int i; 270 271 for (i = 0; i < PTRS_PER_PTE; i++, pte++) { 272 addr = start + i * PAGE_SIZE; 273 note_page(st, addr, 4, pte_val(*pte), PAGE_SIZE); 274 275 } 276 } 277 278 static void walk_hugepd(struct pg_state *st, hugepd_t *phpd, unsigned long start, 279 int pdshift, int level) 280 { 281 #ifdef CONFIG_ARCH_HAS_HUGEPD 282 unsigned int i; 283 int shift = hugepd_shift(*phpd); 284 int ptrs_per_hpd = pdshift - shift > 0 ? 1 << (pdshift - shift) : 1; 285 286 if (start & ((1 << shift) - 1)) 287 return; 288 289 for (i = 0; i < ptrs_per_hpd; i++) { 290 unsigned long addr = start + (i << shift); 291 pte_t *pte = hugepte_offset(*phpd, addr, pdshift); 292 293 note_page(st, addr, level + 1, pte_val(*pte), 1 << shift); 294 } 295 #endif 296 } 297 298 static void walk_pmd(struct pg_state *st, pud_t *pud, unsigned long start) 299 { 300 pmd_t *pmd = pmd_offset(pud, 0); 301 unsigned long addr; 302 unsigned int i; 303 304 for (i = 0; i < PTRS_PER_PMD; i++, pmd++) { 305 addr = start + i * PMD_SIZE; 306 if (!pmd_none(*pmd) && !pmd_is_leaf(*pmd)) 307 /* pmd exists */ 308 walk_pte(st, pmd, addr); 309 else 310 note_page(st, addr, 3, pmd_val(*pmd), PMD_SIZE); 311 } 312 } 313 314 static void walk_pud(struct pg_state *st, p4d_t *p4d, unsigned long start) 315 { 316 pud_t *pud = pud_offset(p4d, 0); 317 unsigned long addr; 318 unsigned int i; 319 320 for (i = 0; i < PTRS_PER_PUD; i++, pud++) { 321 addr = start + i * PUD_SIZE; 322 if (!pud_none(*pud) && !pud_is_leaf(*pud)) 323 /* pud exists */ 324 walk_pmd(st, pud, addr); 325 else 326 note_page(st, addr, 2, pud_val(*pud), PUD_SIZE); 327 } 328 } 329 330 static void walk_pagetables(struct pg_state *st) 331 { 332 unsigned int i; 333 unsigned long addr = st->start_address & PGDIR_MASK; 334 pgd_t *pgd = pgd_offset_k(addr); 335 336 /* 337 * Traverse the linux pagetable structure and dump pages that are in 338 * the hash pagetable. 339 */ 340 for (i = pgd_index(addr); i < PTRS_PER_PGD; i++, pgd++, addr += PGDIR_SIZE) { 341 p4d_t *p4d = p4d_offset(pgd, 0); 342 343 if (p4d_none(*p4d) || p4d_is_leaf(*p4d)) 344 note_page(st, addr, 1, p4d_val(*p4d), PGDIR_SIZE); 345 else if (is_hugepd(__hugepd(p4d_val(*p4d)))) 346 walk_hugepd(st, (hugepd_t *)p4d, addr, PGDIR_SHIFT, 1); 347 else 348 /* p4d exists */ 349 walk_pud(st, p4d, addr); 350 } 351 } 352 353 static void populate_markers(void) 354 { 355 int i = 0; 356 357 #ifdef CONFIG_PPC64 358 address_markers[i++].start_address = PAGE_OFFSET; 359 #else 360 address_markers[i++].start_address = TASK_SIZE; 361 #endif 362 #ifdef MODULES_VADDR 363 address_markers[i++].start_address = MODULES_VADDR; 364 address_markers[i++].start_address = MODULES_END; 365 #endif 366 address_markers[i++].start_address = VMALLOC_START; 367 address_markers[i++].start_address = VMALLOC_END; 368 #ifdef CONFIG_PPC64 369 address_markers[i++].start_address = ISA_IO_BASE; 370 address_markers[i++].start_address = ISA_IO_END; 371 address_markers[i++].start_address = PHB_IO_BASE; 372 address_markers[i++].start_address = PHB_IO_END; 373 address_markers[i++].start_address = IOREMAP_BASE; 374 address_markers[i++].start_address = IOREMAP_END; 375 /* What is the ifdef about? */ 376 #ifdef CONFIG_PPC_BOOK3S_64 377 address_markers[i++].start_address = H_VMEMMAP_START; 378 #else 379 address_markers[i++].start_address = VMEMMAP_BASE; 380 #endif 381 #else /* !CONFIG_PPC64 */ 382 address_markers[i++].start_address = ioremap_bot; 383 address_markers[i++].start_address = IOREMAP_TOP; 384 #ifdef CONFIG_HIGHMEM 385 address_markers[i++].start_address = PKMAP_BASE; 386 address_markers[i++].start_address = PKMAP_ADDR(LAST_PKMAP); 387 #endif 388 address_markers[i++].start_address = FIXADDR_START; 389 address_markers[i++].start_address = FIXADDR_TOP; 390 #ifdef CONFIG_KASAN 391 address_markers[i++].start_address = KASAN_SHADOW_START; 392 address_markers[i++].start_address = KASAN_SHADOW_END; 393 #endif 394 #endif /* CONFIG_PPC64 */ 395 } 396 397 static int ptdump_show(struct seq_file *m, void *v) 398 { 399 struct pg_state st = { 400 .seq = m, 401 .marker = address_markers, 402 .start_address = IS_ENABLED(CONFIG_PPC64) ? PAGE_OFFSET : TASK_SIZE, 403 }; 404 405 #ifdef CONFIG_PPC64 406 if (!radix_enabled()) 407 st.start_address = KERN_VIRT_START; 408 #endif 409 410 /* Traverse kernel page tables */ 411 walk_pagetables(&st); 412 note_page(&st, 0, 0, 0, 0); 413 return 0; 414 } 415 416 417 static int ptdump_open(struct inode *inode, struct file *file) 418 { 419 return single_open(file, ptdump_show, NULL); 420 } 421 422 static const struct file_operations ptdump_fops = { 423 .open = ptdump_open, 424 .read = seq_read, 425 .llseek = seq_lseek, 426 .release = single_release, 427 }; 428 429 static void build_pgtable_complete_mask(void) 430 { 431 unsigned int i, j; 432 433 for (i = 0; i < ARRAY_SIZE(pg_level); i++) 434 if (pg_level[i].flag) 435 for (j = 0; j < pg_level[i].num; j++) 436 pg_level[i].mask |= pg_level[i].flag[j].mask; 437 } 438 439 #ifdef CONFIG_PPC_DEBUG_WX 440 void ptdump_check_wx(void) 441 { 442 struct pg_state st = { 443 .seq = NULL, 444 .marker = address_markers, 445 .check_wx = true, 446 .start_address = IS_ENABLED(CONFIG_PPC64) ? PAGE_OFFSET : TASK_SIZE, 447 }; 448 449 #ifdef CONFIG_PPC64 450 if (!radix_enabled()) 451 st.start_address = KERN_VIRT_START; 452 #endif 453 454 walk_pagetables(&st); 455 456 if (st.wx_pages) 457 pr_warn("Checked W+X mappings: FAILED, %lu W+X pages found\n", 458 st.wx_pages); 459 else 460 pr_info("Checked W+X mappings: passed, no W+X pages found\n"); 461 } 462 #endif 463 464 static int ptdump_init(void) 465 { 466 populate_markers(); 467 build_pgtable_complete_mask(); 468 debugfs_create_file("kernel_page_tables", 0400, NULL, NULL, 469 &ptdump_fops); 470 return 0; 471 } 472 device_initcall(ptdump_init); 473