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 <asm/page.h> 25 #include <asm/hugetlb.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 ptdump_state ptdump; 59 struct seq_file *seq; 60 const struct addr_marker *marker; 61 unsigned long start_address; 62 unsigned long start_pa; 63 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 static struct ptdump_range ptdump_range[] __ro_after_init = { 108 {TASK_SIZE_MAX, ~0UL}, 109 {0, 0} 110 }; 111 112 #define pt_dump_seq_printf(m, fmt, args...) \ 113 ({ \ 114 if (m) \ 115 seq_printf(m, fmt, ##args); \ 116 }) 117 118 #define pt_dump_seq_putc(m, c) \ 119 ({ \ 120 if (m) \ 121 seq_putc(m, c); \ 122 }) 123 124 void pt_dump_size(struct seq_file *m, unsigned long size) 125 { 126 static const char units[] = " KMGTPE"; 127 const char *unit = units; 128 129 /* Work out what appropriate unit to use */ 130 while (!(size & 1023) && unit[1]) { 131 size >>= 10; 132 unit++; 133 } 134 pt_dump_seq_printf(m, "%9lu%c ", size, *unit); 135 } 136 137 static void dump_flag_info(struct pg_state *st, const struct flag_info 138 *flag, u64 pte, int num) 139 { 140 unsigned int i; 141 142 for (i = 0; i < num; i++, flag++) { 143 const char *s = NULL; 144 u64 val; 145 146 /* flag not defined so don't check it */ 147 if (flag->mask == 0) 148 continue; 149 /* Some 'flags' are actually values */ 150 if (flag->is_val) { 151 val = pte & flag->val; 152 if (flag->shift) 153 val = val >> flag->shift; 154 pt_dump_seq_printf(st->seq, " %s:%llx", flag->set, val); 155 } else { 156 if ((pte & flag->mask) == flag->val) 157 s = flag->set; 158 else 159 s = flag->clear; 160 if (s) 161 pt_dump_seq_printf(st->seq, " %s", s); 162 } 163 st->current_flags &= ~flag->mask; 164 } 165 if (st->current_flags != 0) 166 pt_dump_seq_printf(st->seq, " unknown flags:%llx", st->current_flags); 167 } 168 169 static void dump_addr(struct pg_state *st, unsigned long addr) 170 { 171 #ifdef CONFIG_PPC64 172 #define REG "0x%016lx" 173 #else 174 #define REG "0x%08lx" 175 #endif 176 177 pt_dump_seq_printf(st->seq, REG "-" REG " ", st->start_address, addr - 1); 178 pt_dump_seq_printf(st->seq, " " REG " ", st->start_pa); 179 pt_dump_size(st->seq, addr - st->start_address); 180 } 181 182 static void note_prot_wx(struct pg_state *st, unsigned long addr) 183 { 184 pte_t pte = __pte(st->current_flags); 185 186 if (!IS_ENABLED(CONFIG_DEBUG_WX) || !st->check_wx) 187 return; 188 189 if (!pte_write(pte) || !pte_exec(pte)) 190 return; 191 192 WARN_ONCE(1, "powerpc/mm: Found insecure W+X mapping at address %p/%pS\n", 193 (void *)st->start_address, (void *)st->start_address); 194 195 st->wx_pages += (addr - st->start_address) / PAGE_SIZE; 196 } 197 198 static void note_page_update_state(struct pg_state *st, unsigned long addr, int level, u64 val) 199 { 200 u64 flag = level >= 0 ? val & pg_level[level].mask : 0; 201 u64 pa = val & PTE_RPN_MASK; 202 203 st->level = level; 204 st->current_flags = flag; 205 st->start_address = addr; 206 st->start_pa = pa; 207 208 while (addr >= st->marker[1].start_address) { 209 st->marker++; 210 pt_dump_seq_printf(st->seq, "---[ %s ]---\n", st->marker->name); 211 } 212 } 213 214 static void note_page(struct ptdump_state *pt_st, unsigned long addr, int level, u64 val) 215 { 216 u64 flag = level >= 0 ? val & pg_level[level].mask : 0; 217 struct pg_state *st = container_of(pt_st, struct pg_state, ptdump); 218 219 /* At first no level is set */ 220 if (st->level == -1) { 221 pt_dump_seq_printf(st->seq, "---[ %s ]---\n", st->marker->name); 222 note_page_update_state(st, addr, level, val); 223 /* 224 * Dump the section of virtual memory when: 225 * - the PTE flags from one entry to the next differs. 226 * - we change levels in the tree. 227 * - the address is in a different section of memory and is thus 228 * used for a different purpose, regardless of the flags. 229 */ 230 } else if (flag != st->current_flags || level != st->level || 231 addr >= st->marker[1].start_address) { 232 233 /* Check the PTE flags */ 234 if (st->current_flags) { 235 note_prot_wx(st, addr); 236 dump_addr(st, addr); 237 238 /* Dump all the flags */ 239 if (pg_level[st->level].flag) 240 dump_flag_info(st, pg_level[st->level].flag, 241 st->current_flags, 242 pg_level[st->level].num); 243 244 pt_dump_seq_putc(st->seq, '\n'); 245 } 246 247 /* 248 * Address indicates we have passed the end of the 249 * current section of virtual memory 250 */ 251 note_page_update_state(st, addr, level, val); 252 } 253 } 254 255 static void populate_markers(void) 256 { 257 int i = 0; 258 259 #ifdef CONFIG_PPC64 260 address_markers[i++].start_address = PAGE_OFFSET; 261 #else 262 address_markers[i++].start_address = TASK_SIZE; 263 #endif 264 #ifdef MODULES_VADDR 265 address_markers[i++].start_address = MODULES_VADDR; 266 address_markers[i++].start_address = MODULES_END; 267 #endif 268 address_markers[i++].start_address = VMALLOC_START; 269 address_markers[i++].start_address = VMALLOC_END; 270 #ifdef CONFIG_PPC64 271 address_markers[i++].start_address = ISA_IO_BASE; 272 address_markers[i++].start_address = ISA_IO_END; 273 address_markers[i++].start_address = PHB_IO_BASE; 274 address_markers[i++].start_address = PHB_IO_END; 275 address_markers[i++].start_address = IOREMAP_BASE; 276 address_markers[i++].start_address = IOREMAP_END; 277 /* What is the ifdef about? */ 278 #ifdef CONFIG_PPC_BOOK3S_64 279 address_markers[i++].start_address = H_VMEMMAP_START; 280 #else 281 address_markers[i++].start_address = VMEMMAP_BASE; 282 #endif 283 #else /* !CONFIG_PPC64 */ 284 address_markers[i++].start_address = ioremap_bot; 285 address_markers[i++].start_address = IOREMAP_TOP; 286 #ifdef CONFIG_HIGHMEM 287 address_markers[i++].start_address = PKMAP_BASE; 288 address_markers[i++].start_address = PKMAP_ADDR(LAST_PKMAP); 289 #endif 290 address_markers[i++].start_address = FIXADDR_START; 291 address_markers[i++].start_address = FIXADDR_TOP; 292 #ifdef CONFIG_KASAN 293 address_markers[i++].start_address = KASAN_SHADOW_START; 294 address_markers[i++].start_address = KASAN_SHADOW_END; 295 #endif 296 #endif /* CONFIG_PPC64 */ 297 } 298 299 static int ptdump_show(struct seq_file *m, void *v) 300 { 301 struct pg_state st = { 302 .seq = m, 303 .marker = address_markers, 304 .level = -1, 305 .ptdump = { 306 .note_page = note_page, 307 .range = ptdump_range, 308 } 309 }; 310 311 /* Traverse kernel page tables */ 312 ptdump_walk_pgd(&st.ptdump, &init_mm, NULL); 313 return 0; 314 } 315 316 DEFINE_SHOW_ATTRIBUTE(ptdump); 317 318 static void __init build_pgtable_complete_mask(void) 319 { 320 unsigned int i, j; 321 322 for (i = 0; i < ARRAY_SIZE(pg_level); i++) 323 if (pg_level[i].flag) 324 for (j = 0; j < pg_level[i].num; j++) 325 pg_level[i].mask |= pg_level[i].flag[j].mask; 326 } 327 328 #ifdef CONFIG_DEBUG_WX 329 void ptdump_check_wx(void) 330 { 331 struct pg_state st = { 332 .seq = NULL, 333 .marker = (struct addr_marker[]) { 334 { 0, NULL}, 335 { -1, NULL}, 336 }, 337 .level = -1, 338 .check_wx = true, 339 .ptdump = { 340 .note_page = note_page, 341 .range = ptdump_range, 342 } 343 }; 344 345 ptdump_walk_pgd(&st.ptdump, &init_mm, NULL); 346 347 if (st.wx_pages) 348 pr_warn("Checked W+X mappings: FAILED, %lu W+X pages found\n", 349 st.wx_pages); 350 else 351 pr_info("Checked W+X mappings: passed, no W+X pages found\n"); 352 } 353 #endif 354 355 static int __init ptdump_init(void) 356 { 357 #ifdef CONFIG_PPC64 358 if (!radix_enabled()) 359 ptdump_range[0].start = KERN_VIRT_START; 360 else 361 ptdump_range[0].start = PAGE_OFFSET; 362 363 ptdump_range[0].end = PAGE_OFFSET + (PGDIR_SIZE * PTRS_PER_PGD); 364 #endif 365 366 populate_markers(); 367 build_pgtable_complete_mask(); 368 369 if (IS_ENABLED(CONFIG_PTDUMP_DEBUGFS)) 370 debugfs_create_file("kernel_page_tables", 0400, NULL, NULL, &ptdump_fops); 371 372 return 0; 373 } 374 device_initcall(ptdump_init); 375