arch/s390/mm/dump_pagetables.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/set_memory.h>
   3 #include <linux/ptdump.h>
   4 #include <linux/seq_file.h>
   5 #include <linux/debugfs.h>
   6 #include <linux/sort.h>
   7 #include <linux/mm.h>
   8 #include <linux/kfence.h>
   9 #include <linux/kasan.h>
  10 #include <asm/kasan.h>
  11 #include <asm/abs_lowcore.h>
  12 #include <asm/nospec-branch.h>
  13 #include <asm/sections.h>
  14 #include <asm/maccess.h>
  15
  16 static unsigned long max_addr;
  17
  18 struct addr_marker {
  19         int is_start;
  20         unsigned long start_address;
  21         unsigned long size;
  22         const char *name;
  23 };
  24
  25 static struct addr_marker *markers;
  26 static unsigned int markers_cnt;
  27
  28 struct pg_state {
  29         struct ptdump_state ptdump;
  30         struct seq_file *seq;
  31         int level;
  32         unsigned int current_prot;
  33         bool check_wx;
  34         unsigned long wx_pages;
  35         unsigned long start_address;
  36         const struct addr_marker *marker;
  37 };
  38
  39 #define pt_dump_seq_printf(m, fmt, args...)     \
  40 ({                                              \
  41         struct seq_file *__m = (m);             \
  42                                                 \
  43         if (__m)                                \
  44                 seq_printf(__m, fmt, ##args);   \
  45 })
  46
  47 #define pt_dump_seq_puts(m, fmt)                \
  48 ({                                              \
  49         struct seq_file *__m = (m);             \
  50                                                 \
  51         if (__m)                                \
  52                 seq_printf(__m, fmt);           \
  53 })
  54
  55 static void print_prot(struct seq_file *m, unsigned int pr, int level)
  56 {
  57         static const char * const level_name[] =
  58                 { "ASCE", "PGD", "PUD", "PMD", "PTE" };
  59
  60         pt_dump_seq_printf(m, "%s ", level_name[level]);
  61         if (pr & _PAGE_INVALID) {
  62                 pt_dump_seq_printf(m, "I\n");
  63                 return;
  64         }
  65         pt_dump_seq_puts(m, (pr & _PAGE_PROTECT) ? "RO " : "RW ");
  66         pt_dump_seq_puts(m, (pr & _PAGE_NOEXEC) ? "NX\n" : "X\n");
  67 }
  68
  69 static void note_prot_wx(struct pg_state *st, unsigned long addr)
  70 {
  71         if (!st->check_wx)
  72                 return;
  73         if (st->current_prot & _PAGE_INVALID)
  74                 return;
  75         if (st->current_prot & _PAGE_PROTECT)
  76                 return;
  77         if (st->current_prot & _PAGE_NOEXEC)
  78                 return;
  79         /*
  80          * The first lowcore page is W+X if spectre mitigations are using
  81          * trampolines or the BEAR enhancements facility is not installed,
  82          * in which case we have two lpswe instructions in lowcore that need
  83          * to be executable.
  84          */
  85         if (addr == PAGE_SIZE && (nospec_uses_trampoline() || !static_key_enabled(&cpu_has_bear)))
  86                 return;
  87         WARN_ONCE(IS_ENABLED(CONFIG_DEBUG_WX),
  88                   "s390/mm: Found insecure W+X mapping at address %pS\n",
  89                   (void *)st->start_address);
  90         st->wx_pages += (addr - st->start_address) / PAGE_SIZE;
  91 }
  92
  93 static void note_page_update_state(struct pg_state *st, unsigned long addr, unsigned int prot, int level)
  94 {
  95         struct seq_file *m = st->seq;
  96
  97         while (addr >= st->marker[1].start_address) {
  98                 st->marker++;
  99                 pt_dump_seq_printf(m, "---[ %s %s ]---\n", st->marker->name,
 100                                    st->marker->is_start ? "Start" : "End");
 101         }
 102         st->start_address = addr;
 103         st->current_prot = prot;
 104         st->level = level;
 105 }
 106
 107 static void note_page(struct ptdump_state *pt_st, unsigned long addr, int level, u64 val)
 108 {
 109         int width = sizeof(unsigned long) * 2;
 110         static const char units[] = "KMGTPE";
 111         const char *unit = units;
 112         unsigned long delta;
 113         struct pg_state *st;
 114         struct seq_file *m;
 115         unsigned int prot;
 116
 117         st = container_of(pt_st, struct pg_state, ptdump);
 118         m = st->seq;
 119         prot = val & (_PAGE_PROTECT | _PAGE_NOEXEC);
 120         if (level == 4 && (val & _PAGE_INVALID))
 121                 prot = _PAGE_INVALID;
 122         /* For pmd_none() & friends val gets passed as zero. */
 123         if (level != 4 && !val)
 124                 prot = _PAGE_INVALID;
 125         /* Final flush from generic code. */
 126         if (level == -1)
 127                 addr = max_addr;
 128         if (st->level == -1) {
 129                 pt_dump_seq_puts(m, "---[ Kernel Virtual Address Space ]---\n");
 130                 note_page_update_state(st, addr, prot, level);
 131         } else if (prot != st->current_prot || level != st->level ||
 132                    addr >= st->marker[1].start_address) {
 133                 note_prot_wx(st, addr);
 134                 pt_dump_seq_printf(m, "0x%0*lx-0x%0*lx ",
 135                                    width, st->start_address,
 136                                    width, addr);
 137                 delta = (addr - st->start_address) >> 10;
 138                 while (!(delta & 0x3ff) && unit[1]) {
 139                         delta >>= 10;
 140                         unit++;
 141                 }
 142                 pt_dump_seq_printf(m, "%9lu%c ", delta, *unit);
 143                 print_prot(m, st->current_prot, st->level);
 144                 note_page_update_state(st, addr, prot, level);
 145         }
 146 }
 147
 148 bool ptdump_check_wx(void)
 149 {
 150         struct pg_state st = {
 151                 .ptdump = {
 152                         .note_page = note_page,
 153                         .range = (struct ptdump_range[]) {
 154                                 {.start = 0, .end = max_addr},
 155                                 {.start = 0, .end = 0},
 156                         }
 157                 },
 158                 .seq = NULL,
 159                 .level = -1,
 160                 .current_prot = 0,
 161                 .check_wx = true,
 162                 .wx_pages = 0,
 163                 .start_address = 0,
 164                 .marker = (struct addr_marker[]) {
 165                         { .start_address =  0, .name = NULL},
 166                         { .start_address = -1, .name = NULL},
 167                 },
 168         };
 169
 170         if (!MACHINE_HAS_NX)
 171                 return true;
 172         ptdump_walk_pgd(&st.ptdump, &init_mm, NULL);
 173         if (st.wx_pages) {
 174                 pr_warn("Checked W+X mappings: FAILED, %lu W+X pages found\n", st.wx_pages);
 175
 176                 return false;
 177         } else {
 178                 pr_info("Checked W+X mappings: passed, no %sW+X pages found\n",
 179                         (nospec_uses_trampoline() || !static_key_enabled(&cpu_has_bear)) ?
 180                         "unexpected " : "");
 181
 182                 return true;
 183         }
 184 }
 185
 186 #ifdef CONFIG_PTDUMP_DEBUGFS
 187 static int ptdump_show(struct seq_file *m, void *v)
 188 {
 189         struct pg_state st = {
 190                 .ptdump = {
 191                         .note_page = note_page,
 192                         .range = (struct ptdump_range[]) {
 193                                 {.start = 0, .end = max_addr},
 194                                 {.start = 0, .end = 0},
 195                         }
 196                 },
 197                 .seq = m,
 198                 .level = -1,
 199                 .current_prot = 0,
 200                 .check_wx = false,
 201                 .wx_pages = 0,
 202                 .start_address = 0,
 203                 .marker = markers,
 204         };
 205
 206         get_online_mems();
 207         mutex_lock(&cpa_mutex);
 208         ptdump_walk_pgd(&st.ptdump, &init_mm, NULL);
 209         mutex_unlock(&cpa_mutex);
 210         put_online_mems();
 211         return 0;
 212 }
 213 DEFINE_SHOW_ATTRIBUTE(ptdump);
 214 #endif /* CONFIG_PTDUMP_DEBUGFS */
 215
 216 static int ptdump_cmp(const void *a, const void *b)
 217 {
 218         const struct addr_marker *ama = a;
 219         const struct addr_marker *amb = b;
 220
 221         if (ama->start_address > amb->start_address)
 222                 return 1;
 223         if (ama->start_address < amb->start_address)
 224                 return -1;
 225         /*
 226          * If the start addresses of two markers are identical sort markers in an
 227          * order that considers areas contained within other areas correctly.
 228          */
 229         if (ama->is_start && amb->is_start) {
 230                 if (ama->size > amb->size)
 231                         return -1;
 232                 if (ama->size < amb->size)
 233                         return 1;
 234                 return 0;
 235         }
 236         if (!ama->is_start && !amb->is_start) {
 237                 if (ama->size > amb->size)
 238                         return 1;
 239                 if (ama->size < amb->size)
 240                         return -1;
 241                 return 0;
 242         }
 243         if (ama->is_start)
 244                 return 1;
 245         if (amb->is_start)
 246                 return -1;
 247         return 0;
 248 }
 249
 250 static int add_marker(unsigned long start, unsigned long end, const char *name)
 251 {
 252         size_t oldsize, newsize;
 253
 254         oldsize = markers_cnt * sizeof(*markers);
 255         newsize = oldsize + 2 * sizeof(*markers);
 256         if (!oldsize)
 257                 markers = kvmalloc(newsize, GFP_KERNEL);
 258         else
 259                 markers = kvrealloc(markers, newsize, GFP_KERNEL);
 260         if (!markers)
 261                 goto error;
 262         markers[markers_cnt].is_start = 1;
 263         markers[markers_cnt].start_address = start;
 264         markers[markers_cnt].size = end - start;
 265         markers[markers_cnt].name = name;
 266         markers_cnt++;
 267         markers[markers_cnt].is_start = 0;
 268         markers[markers_cnt].start_address = end;
 269         markers[markers_cnt].size = end - start;
 270         markers[markers_cnt].name = name;
 271         markers_cnt++;
 272         return 0;
 273 error:
 274         markers_cnt = 0;
 275         return -ENOMEM;
 276 }
 277
 278 static int pt_dump_init(void)
 279 {
 280 #ifdef CONFIG_KFENCE
 281         unsigned long kfence_start = (unsigned long)__kfence_pool;
 282 #endif
 283         unsigned long lowcore = (unsigned long)get_lowcore();
 284         int rc;
 285
 286         /*
 287          * Figure out the maximum virtual address being accessible with the
 288          * kernel ASCE. We need this to keep the page table walker functions
 289          * from accessing non-existent entries.
 290          */
 291         max_addr = (get_lowcore()->kernel_asce.val & _REGION_ENTRY_TYPE_MASK) >> 2;
 292         max_addr = 1UL << (max_addr * 11 + 31);
 293         /* start + end markers - must be added first */
 294         rc = add_marker(0, -1UL, NULL);
 295         rc |= add_marker((unsigned long)_stext, (unsigned long)_end, "Kernel Image");
 296         rc |= add_marker(lowcore, lowcore + sizeof(struct lowcore), "Lowcore");
 297         rc |= add_marker(__identity_base, __identity_base + ident_map_size, "Identity Mapping");
 298         rc |= add_marker((unsigned long)__samode31, (unsigned long)__eamode31, "Amode31 Area");
 299         rc |= add_marker(MODULES_VADDR, MODULES_END, "Modules Area");
 300         rc |= add_marker(__abs_lowcore, __abs_lowcore + ABS_LOWCORE_MAP_SIZE, "Lowcore Area");
 301         rc |= add_marker(__memcpy_real_area, __memcpy_real_area + MEMCPY_REAL_SIZE, "Real Memory Copy Area");
 302         rc |= add_marker((unsigned long)vmemmap, (unsigned long)vmemmap + vmemmap_size, "vmemmap Area");
 303         rc |= add_marker(VMALLOC_START, VMALLOC_END, "vmalloc Area");
 304 #ifdef CONFIG_KFENCE
 305         rc |= add_marker(kfence_start, kfence_start + KFENCE_POOL_SIZE, "KFence Pool");
 306 #endif
 307 #ifdef CONFIG_KMSAN
 308         rc |= add_marker(KMSAN_VMALLOC_SHADOW_START, KMSAN_VMALLOC_SHADOW_END, "Kmsan vmalloc Shadow");
 309         rc |= add_marker(KMSAN_VMALLOC_ORIGIN_START, KMSAN_VMALLOC_ORIGIN_END, "Kmsan vmalloc Origins");
 310         rc |= add_marker(KMSAN_MODULES_SHADOW_START, KMSAN_MODULES_SHADOW_END, "Kmsan Modules Shadow");
 311         rc |= add_marker(KMSAN_MODULES_ORIGIN_START, KMSAN_MODULES_ORIGIN_END, "Kmsan Modules Origins");
 312 #endif
 313 #ifdef CONFIG_KASAN
 314         rc |= add_marker(KASAN_SHADOW_START, KASAN_SHADOW_END, "Kasan Shadow");
 315 #endif
 316         if (rc)
 317                 goto error;
 318         sort(&markers[1], markers_cnt - 1, sizeof(*markers), ptdump_cmp, NULL);
 319 #ifdef CONFIG_PTDUMP_DEBUGFS
 320         debugfs_create_file("kernel_page_tables", 0400, NULL, NULL, &ptdump_fops);
 321 #endif /* CONFIG_PTDUMP_DEBUGFS */
 322         return 0;
 323 error:
 324         kvfree(markers);
 325         return -ENOMEM;
 326 }
 327 device_initcall(pt_dump_init);