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 } 182 183 static void note_prot_wx(struct pg_state *st, unsigned long addr) 184 { 185 pte_t pte = __pte(st->current_flags); 186 187 if (!st->check_wx) 188 return; 189 190 if (!pte_write(pte) || !pte_exec(pte)) 191 return; 192 193 WARN_ONCE(IS_ENABLED(CONFIG_DEBUG_WX), 194 "powerpc/mm: Found insecure W+X mapping at address %p/%pS\n", 195 (void *)st->start_address, (void *)st->start_address); 196 197 st->wx_pages += (addr - st->start_address) / PAGE_SIZE; 198 } 199 200 static void note_page_update_state(struct pg_state *st, unsigned long addr, int level, u64 val) 201 { 202 u64 flag = level >= 0 ? val & pg_level[level].mask : 0; 203 u64 pa = val & PTE_RPN_MASK; 204 205 st->level = level; 206 st->current_flags = flag; 207 st->start_address = addr; 208 st->start_pa = pa; 209 210 while (addr >= st->marker[1].start_address) { 211 st->marker++; 212 pt_dump_seq_printf(st->seq, "---[ %s ]---\n", st->marker->name); 213 } 214 } 215 216 static void note_page(struct ptdump_state *pt_st, unsigned long addr, int level, u64 val) 217 { 218 u64 flag = level >= 0 ? val & pg_level[level].mask : 0; 219 struct pg_state *st = container_of(pt_st, struct pg_state, ptdump); 220 221 /* At first no level is set */ 222 if (st->level == -1) { 223 pt_dump_seq_printf(st->seq, "---[ %s ]---\n", st->marker->name); 224 note_page_update_state(st, addr, level, val); 225 /* 226 * Dump the section of virtual memory when: 227 * - the PTE flags from one entry to the next differs. 228 * - we change levels in the tree. 229 * - the address is in a different section of memory and is thus 230 * used for a different purpose, regardless of the flags. 231 */ 232 } else if (flag != st->current_flags || level != st->level || 233 addr >= st->marker[1].start_address) { 234 235 /* Check the PTE flags */ 236 if (st->current_flags) { 237 note_prot_wx(st, addr); 238 dump_addr(st, addr); 239 240 /* Dump all the flags */ 241 if (pg_level[st->level].flag) 242 dump_flag_info(st, pg_level[st->level].flag, 243 st->current_flags, 244 pg_level[st->level].num); 245 246 pt_dump_seq_putc(st->seq, '\n'); 247 } 248 249 /* 250 * Address indicates we have passed the end of the 251 * current section of virtual memory 252 */ 253 note_page_update_state(st, addr, level, val); 254 } 255 } 256 257 static void populate_markers(void) 258 { 259 int i = 0; 260 261 #ifdef CONFIG_PPC64 262 address_markers[i++].start_address = PAGE_OFFSET; 263 #else 264 address_markers[i++].start_address = TASK_SIZE; 265 #endif 266 #ifdef MODULES_VADDR 267 address_markers[i++].start_address = MODULES_VADDR; 268 address_markers[i++].start_address = MODULES_END; 269 #endif 270 address_markers[i++].start_address = VMALLOC_START; 271 address_markers[i++].start_address = VMALLOC_END; 272 #ifdef CONFIG_PPC64 273 address_markers[i++].start_address = ISA_IO_BASE; 274 address_markers[i++].start_address = ISA_IO_END; 275 address_markers[i++].start_address = PHB_IO_BASE; 276 address_markers[i++].start_address = PHB_IO_END; 277 address_markers[i++].start_address = IOREMAP_BASE; 278 address_markers[i++].start_address = IOREMAP_END; 279 /* What is the ifdef about? */ 280 #ifdef CONFIG_PPC_BOOK3S_64 281 address_markers[i++].start_address = H_VMEMMAP_START; 282 #else 283 address_markers[i++].start_address = VMEMMAP_BASE; 284 #endif 285 #else /* !CONFIG_PPC64 */ 286 address_markers[i++].start_address = ioremap_bot; 287 address_markers[i++].start_address = IOREMAP_TOP; 288 #ifdef CONFIG_HIGHMEM 289 address_markers[i++].start_address = PKMAP_BASE; 290 address_markers[i++].start_address = PKMAP_ADDR(LAST_PKMAP); 291 #endif 292 address_markers[i++].start_address = FIXADDR_START; 293 address_markers[i++].start_address = FIXADDR_TOP; 294 #endif /* CONFIG_PPC64 */ 295 #ifdef CONFIG_KASAN 296 address_markers[i++].start_address = KASAN_SHADOW_START; 297 address_markers[i++].start_address = KASAN_SHADOW_END; 298 #endif 299 } 300 301 static int ptdump_show(struct seq_file *m, void *v) 302 { 303 struct pg_state st = { 304 .seq = m, 305 .marker = address_markers, 306 .level = -1, 307 .ptdump = { 308 .note_page = note_page, 309 .range = ptdump_range, 310 } 311 }; 312 313 /* Traverse kernel page tables */ 314 ptdump_walk_pgd(&st.ptdump, &init_mm, NULL); 315 return 0; 316 } 317 318 DEFINE_SHOW_ATTRIBUTE(ptdump); 319 320 static void __init build_pgtable_complete_mask(void) 321 { 322 unsigned int i, j; 323 324 for (i = 0; i < ARRAY_SIZE(pg_level); i++) 325 if (pg_level[i].flag) 326 for (j = 0; j < pg_level[i].num; j++) 327 pg_level[i].mask |= pg_level[i].flag[j].mask; 328 } 329 330 bool ptdump_check_wx(void) 331 { 332 struct pg_state st = { 333 .seq = NULL, 334 .marker = (struct addr_marker[]) { 335 { 0, NULL}, 336 { -1, NULL}, 337 }, 338 .level = -1, 339 .check_wx = true, 340 .ptdump = { 341 .note_page = note_page, 342 .range = ptdump_range, 343 } 344 }; 345 346 if (IS_ENABLED(CONFIG_PPC_BOOK3S_64) && !mmu_has_feature(MMU_FTR_KERNEL_RO)) 347 return true; 348 349 ptdump_walk_pgd(&st.ptdump, &init_mm, NULL); 350 351 if (st.wx_pages) { 352 pr_warn("Checked W+X mappings: FAILED, %lu W+X pages found\n", 353 st.wx_pages); 354 355 return false; 356 } else { 357 pr_info("Checked W+X mappings: passed, no W+X pages found\n"); 358 359 return true; 360 } 361 } 362 363 static int __init ptdump_init(void) 364 { 365 #ifdef CONFIG_PPC64 366 if (!radix_enabled()) 367 ptdump_range[0].start = KERN_VIRT_START; 368 else 369 ptdump_range[0].start = PAGE_OFFSET; 370 371 ptdump_range[0].end = PAGE_OFFSET + (PGDIR_SIZE * PTRS_PER_PGD); 372 #endif 373 374 populate_markers(); 375 build_pgtable_complete_mask(); 376 377 if (IS_ENABLED(CONFIG_PTDUMP_DEBUGFS)) 378 debugfs_create_file("kernel_page_tables", 0400, NULL, NULL, &ptdump_fops); 379 380 return 0; 381 } 382 device_initcall(ptdump_init); 383