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/ptdump.h> 20 #include <linux/sched.h> 21 #include <linux/seq_file.h> 22 #include <asm/fixmap.h> 23 #include <linux/const.h> 24 #include <linux/kasan.h> 25 #include <asm/page.h> 26 #include <asm/hugetlb.h> 27 28 #include <mm/mmu_decl.h> 29 30 #include "ptdump.h" 31 32 /* 33 * To visualise what is happening, 34 * 35 * - PTRS_PER_P** = how many entries there are in the corresponding P** 36 * - P**_SHIFT = how many bits of the address we use to index into the 37 * corresponding P** 38 * - P**_SIZE is how much memory we can access through the table - not the 39 * size of the table itself. 40 * P**={PGD, PUD, PMD, PTE} 41 * 42 * 43 * Each entry of the PGD points to a PUD. Each entry of a PUD points to a 44 * PMD. Each entry of a PMD points to a PTE. And every PTE entry points to 45 * a page. 46 * 47 * In the case where there are only 3 levels, the PUD is folded into the 48 * PGD: every PUD has only one entry which points to the PMD. 49 * 50 * The page dumper groups page table entries of the same type into a single 51 * description. It uses pg_state to track the range information while 52 * iterating over the PTE entries. When the continuity is broken it then 53 * dumps out a description of the range - ie PTEs that are virtually contiguous 54 * with the same PTE flags are chunked together. This is to make it clear how 55 * different areas of the kernel virtual memory are used. 56 * 57 */ 58 struct pg_state { 59 struct ptdump_state ptdump; 60 struct seq_file *seq; 61 const struct addr_marker *marker; 62 unsigned long start_address; 63 unsigned long start_pa; 64 int level; 65 u64 current_flags; 66 bool check_wx; 67 unsigned long wx_pages; 68 }; 69 70 struct addr_marker { 71 unsigned long start_address; 72 const char *name; 73 }; 74 75 static struct addr_marker address_markers[] = { 76 { 0, "Start of kernel VM" }, 77 #ifdef MODULES_VADDR 78 { 0, "modules start" }, 79 { 0, "modules end" }, 80 #endif 81 { 0, "vmalloc() Area" }, 82 { 0, "vmalloc() End" }, 83 #ifdef CONFIG_PPC64 84 { 0, "isa I/O start" }, 85 { 0, "isa I/O end" }, 86 { 0, "phb I/O start" }, 87 { 0, "phb I/O end" }, 88 { 0, "I/O remap start" }, 89 { 0, "I/O remap end" }, 90 { 0, "vmemmap start" }, 91 #else 92 { 0, "Early I/O remap start" }, 93 { 0, "Early I/O remap end" }, 94 #ifdef CONFIG_HIGHMEM 95 { 0, "Highmem PTEs start" }, 96 { 0, "Highmem PTEs end" }, 97 #endif 98 { 0, "Fixmap start" }, 99 { 0, "Fixmap end" }, 100 #endif 101 #ifdef CONFIG_KASAN 102 { 0, "kasan shadow mem start" }, 103 { 0, "kasan shadow mem end" }, 104 #endif 105 { -1, NULL }, 106 }; 107 108 static struct ptdump_range ptdump_range[] __ro_after_init = { 109 {TASK_SIZE_MAX, ~0UL}, 110 {0, 0} 111 }; 112 113 #define pt_dump_seq_printf(m, fmt, args...) \ 114 ({ \ 115 if (m) \ 116 seq_printf(m, fmt, ##args); \ 117 }) 118 119 #define pt_dump_seq_putc(m, c) \ 120 ({ \ 121 if (m) \ 122 seq_putc(m, c); \ 123 }) 124 125 void pt_dump_size(struct seq_file *m, unsigned long size) 126 { 127 static const char units[] = " KMGTPE"; 128 const char *unit = units; 129 130 /* Work out what appropriate unit to use */ 131 while (!(size & 1023) && unit[1]) { 132 size >>= 10; 133 unit++; 134 } 135 pt_dump_seq_printf(m, "%9lu%c ", size, *unit); 136 } 137 138 static void dump_flag_info(struct pg_state *st, const struct flag_info 139 *flag, u64 pte, int num) 140 { 141 unsigned int i; 142 143 for (i = 0; i < num; i++, flag++) { 144 const char *s = NULL; 145 u64 val; 146 147 /* flag not defined so don't check it */ 148 if (flag->mask == 0) 149 continue; 150 /* Some 'flags' are actually values */ 151 if (flag->is_val) { 152 val = pte & flag->val; 153 if (flag->shift) 154 val = val >> flag->shift; 155 pt_dump_seq_printf(st->seq, " %s:%llx", flag->set, val); 156 } else { 157 if ((pte & flag->mask) == flag->val) 158 s = flag->set; 159 else 160 s = flag->clear; 161 if (s) 162 pt_dump_seq_printf(st->seq, " %s", s); 163 } 164 st->current_flags &= ~flag->mask; 165 } 166 if (st->current_flags != 0) 167 pt_dump_seq_printf(st->seq, " unknown flags:%llx", st->current_flags); 168 } 169 170 static void dump_addr(struct pg_state *st, unsigned long addr) 171 { 172 #ifdef CONFIG_PPC64 173 #define REG "0x%016lx" 174 #else 175 #define REG "0x%08lx" 176 #endif 177 178 pt_dump_seq_printf(st->seq, REG "-" REG " ", st->start_address, addr - 1); 179 pt_dump_seq_printf(st->seq, " " REG " ", st->start_pa); 180 pt_dump_size(st->seq, addr - st->start_address); 181 pt_dump_seq_printf(st->seq, "%s ", pg_level[st->level].name); 182 } 183 184 static void note_prot_wx(struct pg_state *st, unsigned long addr) 185 { 186 pte_t pte = __pte(st->current_flags); 187 188 if (!st->check_wx) 189 return; 190 191 if (!pte_write(pte) || !pte_exec(pte)) 192 return; 193 194 WARN_ONCE(IS_ENABLED(CONFIG_DEBUG_WX), 195 "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, int level, u64 val) 202 { 203 u64 flag = level >= 0 ? val & pg_level[level].mask : 0; 204 u64 pa = val & PTE_RPN_MASK; 205 206 st->level = level; 207 st->current_flags = flag; 208 st->start_address = addr; 209 st->start_pa = pa; 210 211 while (addr >= st->marker[1].start_address) { 212 st->marker++; 213 pt_dump_seq_printf(st->seq, "---[ %s ]---\n", st->marker->name); 214 } 215 } 216 217 static void note_page(struct ptdump_state *pt_st, unsigned long addr, int level, u64 val) 218 { 219 u64 flag = level >= 0 ? val & pg_level[level].mask : 0; 220 struct pg_state *st = container_of(pt_st, struct pg_state, ptdump); 221 222 /* At first no level is set */ 223 if (st->level == -1) { 224 pt_dump_seq_printf(st->seq, "---[ %s ]---\n", st->marker->name); 225 note_page_update_state(st, addr, level, val); 226 /* 227 * Dump the section of virtual memory when: 228 * - the PTE flags from one entry to the next differs. 229 * - we change levels in the tree. 230 * - the address is in a different section of memory and is thus 231 * used for a different purpose, regardless of the flags. 232 */ 233 } else if (flag != st->current_flags || level != st->level || 234 addr >= st->marker[1].start_address) { 235 236 /* Check the PTE flags */ 237 if (st->current_flags) { 238 note_prot_wx(st, addr); 239 dump_addr(st, addr); 240 241 /* Dump all the flags */ 242 if (pg_level[st->level].flag) 243 dump_flag_info(st, pg_level[st->level].flag, 244 st->current_flags, 245 pg_level[st->level].num); 246 247 pt_dump_seq_putc(st->seq, '\n'); 248 } 249 250 /* 251 * Address indicates we have passed the end of the 252 * current section of virtual memory 253 */ 254 note_page_update_state(st, addr, level, val); 255 } 256 } 257 258 static void populate_markers(void) 259 { 260 int i = 0; 261 262 #ifdef CONFIG_PPC64 263 address_markers[i++].start_address = PAGE_OFFSET; 264 #else 265 address_markers[i++].start_address = TASK_SIZE; 266 #endif 267 #ifdef MODULES_VADDR 268 address_markers[i++].start_address = MODULES_VADDR; 269 address_markers[i++].start_address = MODULES_END; 270 #endif 271 address_markers[i++].start_address = VMALLOC_START; 272 address_markers[i++].start_address = VMALLOC_END; 273 #ifdef CONFIG_PPC64 274 address_markers[i++].start_address = ISA_IO_BASE; 275 address_markers[i++].start_address = ISA_IO_END; 276 address_markers[i++].start_address = PHB_IO_BASE; 277 address_markers[i++].start_address = PHB_IO_END; 278 address_markers[i++].start_address = IOREMAP_BASE; 279 address_markers[i++].start_address = IOREMAP_END; 280 /* What is the ifdef about? */ 281 #ifdef CONFIG_PPC_BOOK3S_64 282 address_markers[i++].start_address = H_VMEMMAP_START; 283 #else 284 address_markers[i++].start_address = VMEMMAP_BASE; 285 #endif 286 #else /* !CONFIG_PPC64 */ 287 address_markers[i++].start_address = ioremap_bot; 288 address_markers[i++].start_address = IOREMAP_TOP; 289 #ifdef CONFIG_HIGHMEM 290 address_markers[i++].start_address = PKMAP_BASE; 291 address_markers[i++].start_address = PKMAP_ADDR(LAST_PKMAP); 292 #endif 293 address_markers[i++].start_address = FIXADDR_START; 294 address_markers[i++].start_address = FIXADDR_TOP; 295 #endif /* CONFIG_PPC64 */ 296 #ifdef CONFIG_KASAN 297 address_markers[i++].start_address = KASAN_SHADOW_START; 298 address_markers[i++].start_address = KASAN_SHADOW_END; 299 #endif 300 } 301 302 static void note_page_pte(struct ptdump_state *pt_st, unsigned long addr, pte_t pte) 303 { 304 note_page(pt_st, addr, 4, pte_val(pte)); 305 } 306 307 static void note_page_pmd(struct ptdump_state *pt_st, unsigned long addr, pmd_t pmd) 308 { 309 note_page(pt_st, addr, 3, pmd_val(pmd)); 310 } 311 312 static void note_page_pud(struct ptdump_state *pt_st, unsigned long addr, pud_t pud) 313 { 314 note_page(pt_st, addr, 2, pud_val(pud)); 315 } 316 317 static void note_page_p4d(struct ptdump_state *pt_st, unsigned long addr, p4d_t p4d) 318 { 319 note_page(pt_st, addr, 1, p4d_val(p4d)); 320 } 321 322 static void note_page_pgd(struct ptdump_state *pt_st, unsigned long addr, pgd_t pgd) 323 { 324 note_page(pt_st, addr, 0, pgd_val(pgd)); 325 } 326 327 static void note_page_flush(struct ptdump_state *pt_st) 328 { 329 pte_t pte_zero = {0}; 330 331 note_page(pt_st, 0, -1, pte_val(pte_zero)); 332 } 333 334 static int ptdump_show(struct seq_file *m, void *v) 335 { 336 struct pg_state st = { 337 .seq = m, 338 .marker = address_markers, 339 .level = -1, 340 .ptdump = { 341 .note_page_pte = note_page_pte, 342 .note_page_pmd = note_page_pmd, 343 .note_page_pud = note_page_pud, 344 .note_page_p4d = note_page_p4d, 345 .note_page_pgd = note_page_pgd, 346 .note_page_flush = note_page_flush, 347 .range = ptdump_range, 348 } 349 }; 350 351 /* Traverse kernel page tables */ 352 ptdump_walk_pgd(&st.ptdump, &init_mm, NULL); 353 return 0; 354 } 355 356 DEFINE_SHOW_ATTRIBUTE(ptdump); 357 358 static void __init build_pgtable_complete_mask(void) 359 { 360 unsigned int i, j; 361 362 for (i = 0; i < ARRAY_SIZE(pg_level); i++) 363 if (pg_level[i].flag) 364 for (j = 0; j < pg_level[i].num; j++) 365 pg_level[i].mask |= pg_level[i].flag[j].mask; 366 } 367 368 bool ptdump_check_wx(void) 369 { 370 struct pg_state st = { 371 .seq = NULL, 372 .marker = (struct addr_marker[]) { 373 { 0, NULL}, 374 { -1, NULL}, 375 }, 376 .level = -1, 377 .check_wx = true, 378 .ptdump = { 379 .note_page_pte = note_page_pte, 380 .note_page_pmd = note_page_pmd, 381 .note_page_pud = note_page_pud, 382 .note_page_p4d = note_page_p4d, 383 .note_page_pgd = note_page_pgd, 384 .note_page_flush = note_page_flush, 385 .range = ptdump_range, 386 } 387 }; 388 389 if (IS_ENABLED(CONFIG_PPC_BOOK3S_64) && !mmu_has_feature(MMU_FTR_KERNEL_RO)) 390 return true; 391 392 ptdump_walk_pgd(&st.ptdump, &init_mm, NULL); 393 394 if (st.wx_pages) { 395 pr_warn("Checked W+X mappings: FAILED, %lu W+X pages found\n", 396 st.wx_pages); 397 398 return false; 399 } else { 400 pr_info("Checked W+X mappings: passed, no W+X pages found\n"); 401 402 return true; 403 } 404 } 405 406 static int __init ptdump_init(void) 407 { 408 #ifdef CONFIG_PPC64 409 if (!radix_enabled()) 410 ptdump_range[0].start = KERN_VIRT_START; 411 else 412 ptdump_range[0].start = PAGE_OFFSET; 413 414 ptdump_range[0].end = PAGE_OFFSET + (PGDIR_SIZE * PTRS_PER_PGD); 415 #endif 416 417 populate_markers(); 418 build_pgtable_complete_mask(); 419 420 if (IS_ENABLED(CONFIG_PTDUMP_DEBUGFS)) 421 debugfs_create_file("kernel_page_tables", 0400, NULL, NULL, &ptdump_fops); 422 423 return 0; 424 } 425 device_initcall(ptdump_init); 426