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