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