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/mm.h>
   7 #include <linux/kfence.h>
   8 #include <linux/kasan.h>
   9 #include <asm/kasan.h>
  10 #include <asm/abs_lowcore.h>
  11 #include <asm/nospec-branch.h>
  12 #include <asm/sections.h>
  13 #include <asm/maccess.h>
  14
  15 static unsigned long max_addr;
  16
  17 struct addr_marker {
  18         unsigned long start_address;
  19         const char *name;
  20 };
  21
  22 enum address_markers_idx {
  23         IDENTITY_BEFORE_NR = 0,
  24         IDENTITY_BEFORE_END_NR,
  25         AMODE31_START_NR,
  26         AMODE31_END_NR,
  27         KERNEL_START_NR,
  28         KERNEL_END_NR,
  29 #ifdef CONFIG_KFENCE
  30         KFENCE_START_NR,
  31         KFENCE_END_NR,
  32 #endif
  33         IDENTITY_AFTER_NR,
  34         IDENTITY_AFTER_END_NR,
  35         VMEMMAP_NR,
  36         VMEMMAP_END_NR,
  37         VMALLOC_NR,
  38         VMALLOC_END_NR,
  39         MODULES_NR,
  40         MODULES_END_NR,
  41         ABS_LOWCORE_NR,
  42         ABS_LOWCORE_END_NR,
  43         MEMCPY_REAL_NR,
  44         MEMCPY_REAL_END_NR,
  45 #ifdef CONFIG_KASAN
  46         KASAN_SHADOW_START_NR,
  47         KASAN_SHADOW_END_NR,
  48 #endif
  49 };
  50
  51 static struct addr_marker address_markers[] = {
  52         [IDENTITY_BEFORE_NR]    = {0, "Identity Mapping Start"},
  53         [IDENTITY_BEFORE_END_NR] = {(unsigned long)_stext, "Identity Mapping End"},
  54         [AMODE31_START_NR]      = {0, "Amode31 Area Start"},
  55         [AMODE31_END_NR]        = {0, "Amode31 Area End"},
  56         [KERNEL_START_NR]       = {(unsigned long)_stext, "Kernel Image Start"},
  57         [KERNEL_END_NR]         = {(unsigned long)_end, "Kernel Image End"},
  58 #ifdef CONFIG_KFENCE
  59         [KFENCE_START_NR]       = {0, "KFence Pool Start"},
  60         [KFENCE_END_NR]         = {0, "KFence Pool End"},
  61 #endif
  62         [IDENTITY_AFTER_NR]     = {(unsigned long)_end, "Identity Mapping Start"},
  63         [IDENTITY_AFTER_END_NR] = {0, "Identity Mapping End"},
  64         [VMEMMAP_NR]            = {0, "vmemmap Area Start"},
  65         [VMEMMAP_END_NR]        = {0, "vmemmap Area End"},
  66         [VMALLOC_NR]            = {0, "vmalloc Area Start"},
  67         [VMALLOC_END_NR]        = {0, "vmalloc Area End"},
  68         [MODULES_NR]            = {0, "Modules Area Start"},
  69         [MODULES_END_NR]        = {0, "Modules Area End"},
  70         [ABS_LOWCORE_NR]        = {0, "Lowcore Area Start"},
  71         [ABS_LOWCORE_END_NR]    = {0, "Lowcore Area End"},
  72         [MEMCPY_REAL_NR]        = {0, "Real Memory Copy Area Start"},
  73         [MEMCPY_REAL_END_NR]    = {0, "Real Memory Copy Area End"},
  74 #ifdef CONFIG_KASAN
  75         [KASAN_SHADOW_START_NR] = {KASAN_SHADOW_START, "Kasan Shadow Start"},
  76         [KASAN_SHADOW_END_NR]   = {KASAN_SHADOW_END, "Kasan Shadow End"},
  77 #endif
  78         { -1, NULL }
  79 };
  80
  81 struct pg_state {
  82         struct ptdump_state ptdump;
  83         struct seq_file *seq;
  84         int level;
  85         unsigned int current_prot;
  86         bool check_wx;
  87         unsigned long wx_pages;
  88         unsigned long start_address;
  89         const struct addr_marker *marker;
  90 };
  91
  92 #define pt_dump_seq_printf(m, fmt, args...)     \
  93 ({                                              \
  94         struct seq_file *__m = (m);             \
  95                                                 \
  96         if (__m)                                \
  97                 seq_printf(__m, fmt, ##args);   \
  98 })
  99
 100 #define pt_dump_seq_puts(m, fmt)                \
 101 ({                                              \
 102         struct seq_file *__m = (m);             \
 103                                                 \
 104         if (__m)                                \
 105                 seq_printf(__m, fmt);           \
 106 })
 107
 108 static void print_prot(struct seq_file *m, unsigned int pr, int level)
 109 {
 110         static const char * const level_name[] =
 111                 { "ASCE", "PGD", "PUD", "PMD", "PTE" };
 112
 113         pt_dump_seq_printf(m, "%s ", level_name[level]);
 114         if (pr & _PAGE_INVALID) {
 115                 pt_dump_seq_printf(m, "I\n");
 116                 return;
 117         }
 118         pt_dump_seq_puts(m, (pr & _PAGE_PROTECT) ? "RO " : "RW ");
 119         pt_dump_seq_puts(m, (pr & _PAGE_NOEXEC) ? "NX\n" : "X\n");
 120 }
 121
 122 static void note_prot_wx(struct pg_state *st, unsigned long addr)
 123 {
 124         if (!st->check_wx)
 125                 return;
 126         if (st->current_prot & _PAGE_INVALID)
 127                 return;
 128         if (st->current_prot & _PAGE_PROTECT)
 129                 return;
 130         if (st->current_prot & _PAGE_NOEXEC)
 131                 return;
 132         /*
 133          * The first lowcore page is W+X if spectre mitigations are using
 134          * trampolines or the BEAR enhancements facility is not installed,
 135          * in which case we have two lpswe instructions in lowcore that need
 136          * to be executable.
 137          */
 138         if (addr == PAGE_SIZE && (nospec_uses_trampoline() || !static_key_enabled(&cpu_has_bear)))
 139                 return;
 140         WARN_ONCE(IS_ENABLED(CONFIG_DEBUG_WX),
 141                   "s390/mm: Found insecure W+X mapping at address %pS\n",
 142                   (void *)st->start_address);
 143         st->wx_pages += (addr - st->start_address) / PAGE_SIZE;
 144 }
 145
 146 static void note_page(struct ptdump_state *pt_st, unsigned long addr, int level, u64 val)
 147 {
 148         int width = sizeof(unsigned long) * 2;
 149         static const char units[] = "KMGTPE";
 150         const char *unit = units;
 151         unsigned long delta;
 152         struct pg_state *st;
 153         struct seq_file *m;
 154         unsigned int prot;
 155
 156         st = container_of(pt_st, struct pg_state, ptdump);
 157         m = st->seq;
 158         prot = val & (_PAGE_PROTECT | _PAGE_NOEXEC);
 159         if (level == 4 && (val & _PAGE_INVALID))
 160                 prot = _PAGE_INVALID;
 161         /* For pmd_none() & friends val gets passed as zero. */
 162         if (level != 4 && !val)
 163                 prot = _PAGE_INVALID;
 164         /* Final flush from generic code. */
 165         if (level == -1)
 166                 addr = max_addr;
 167         if (st->level == -1) {
 168                 pt_dump_seq_printf(m, "---[ %s ]---\n", st->marker->name);
 169                 st->start_address = addr;
 170                 st->current_prot = prot;
 171                 st->level = level;
 172         } else if (prot != st->current_prot || level != st->level ||
 173                    addr >= st->marker[1].start_address) {
 174                 note_prot_wx(st, addr);
 175                 pt_dump_seq_printf(m, "0x%0*lx-0x%0*lx ",
 176                                    width, st->start_address,
 177                                    width, addr);
 178                 delta = (addr - st->start_address) >> 10;
 179                 while (!(delta & 0x3ff) && unit[1]) {
 180                         delta >>= 10;
 181                         unit++;
 182                 }
 183                 pt_dump_seq_printf(m, "%9lu%c ", delta, *unit);
 184                 print_prot(m, st->current_prot, st->level);
 185                 while (addr >= st->marker[1].start_address) {
 186                         st->marker++;
 187                         pt_dump_seq_printf(m, "---[ %s ]---\n", st->marker->name);
 188                 }
 189                 st->start_address = addr;
 190                 st->current_prot = prot;
 191                 st->level = level;
 192         }
 193 }
 194
 195 bool ptdump_check_wx(void)
 196 {
 197         struct pg_state st = {
 198                 .ptdump = {
 199                         .note_page = note_page,
 200                         .range = (struct ptdump_range[]) {
 201                                 {.start = 0, .end = max_addr},
 202                                 {.start = 0, .end = 0},
 203                         }
 204                 },
 205                 .seq = NULL,
 206                 .level = -1,
 207                 .current_prot = 0,
 208                 .check_wx = true,
 209                 .wx_pages = 0,
 210                 .start_address = 0,
 211                 .marker = (struct addr_marker[]) {
 212                         { .start_address =  0, .name = NULL},
 213                         { .start_address = -1, .name = NULL},
 214                 },
 215         };
 216
 217         if (!MACHINE_HAS_NX)
 218                 return true;
 219         ptdump_walk_pgd(&st.ptdump, &init_mm, NULL);
 220         if (st.wx_pages) {
 221                 pr_warn("Checked W+X mappings: FAILED, %lu W+X pages found\n", st.wx_pages);
 222
 223                 return false;
 224         } else {
 225                 pr_info("Checked W+X mappings: passed, no %sW+X pages found\n",
 226                         (nospec_uses_trampoline() || !static_key_enabled(&cpu_has_bear)) ?
 227                         "unexpected " : "");
 228
 229                 return true;
 230         }
 231 }
 232
 233 #ifdef CONFIG_PTDUMP_DEBUGFS
 234 static int ptdump_show(struct seq_file *m, void *v)
 235 {
 236         struct pg_state st = {
 237                 .ptdump = {
 238                         .note_page = note_page,
 239                         .range = (struct ptdump_range[]) {
 240                                 {.start = 0, .end = max_addr},
 241                                 {.start = 0, .end = 0},
 242                         }
 243                 },
 244                 .seq = m,
 245                 .level = -1,
 246                 .current_prot = 0,
 247                 .check_wx = false,
 248                 .wx_pages = 0,
 249                 .start_address = 0,
 250                 .marker = address_markers,
 251         };
 252
 253         get_online_mems();
 254         mutex_lock(&cpa_mutex);
 255         ptdump_walk_pgd(&st.ptdump, &init_mm, NULL);
 256         mutex_unlock(&cpa_mutex);
 257         put_online_mems();
 258         return 0;
 259 }
 260 DEFINE_SHOW_ATTRIBUTE(ptdump);
 261 #endif /* CONFIG_PTDUMP_DEBUGFS */
 262
 263 /*
 264  * Heapsort from lib/sort.c is not a stable sorting algorithm, do a simple
 265  * insertion sort to preserve the original order of markers with the same
 266  * start address.
 267  */
 268 static void sort_address_markers(void)
 269 {
 270         struct addr_marker tmp;
 271         int i, j;
 272
 273         for (i = 1; i < ARRAY_SIZE(address_markers) - 1; i++) {
 274                 tmp = address_markers[i];
 275                 for (j = i - 1; j >= 0 && address_markers[j].start_address > tmp.start_address; j--)
 276                         address_markers[j + 1] = address_markers[j];
 277                 address_markers[j + 1] = tmp;
 278         }
 279 }
 280
 281 static int pt_dump_init(void)
 282 {
 283 #ifdef CONFIG_KFENCE
 284         unsigned long kfence_start = (unsigned long)__kfence_pool;
 285 #endif
 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 = (S390_lowcore.kernel_asce.val & _REGION_ENTRY_TYPE_MASK) >> 2;
 292         max_addr = 1UL << (max_addr * 11 + 31);
 293         address_markers[IDENTITY_AFTER_END_NR].start_address = ident_map_size;
 294         address_markers[AMODE31_START_NR].start_address = (unsigned long)__samode31;
 295         address_markers[AMODE31_END_NR].start_address = (unsigned long)__eamode31;
 296         address_markers[MODULES_NR].start_address = MODULES_VADDR;
 297         address_markers[MODULES_END_NR].start_address = MODULES_END;
 298         address_markers[ABS_LOWCORE_NR].start_address = __abs_lowcore;
 299         address_markers[ABS_LOWCORE_END_NR].start_address = __abs_lowcore + ABS_LOWCORE_MAP_SIZE;
 300         address_markers[MEMCPY_REAL_NR].start_address = __memcpy_real_area;
 301         address_markers[MEMCPY_REAL_END_NR].start_address = __memcpy_real_area + MEMCPY_REAL_SIZE;
 302         address_markers[VMEMMAP_NR].start_address = (unsigned long) vmemmap;
 303         address_markers[VMEMMAP_END_NR].start_address = (unsigned long)vmemmap + vmemmap_size;
 304         address_markers[VMALLOC_NR].start_address = VMALLOC_START;
 305         address_markers[VMALLOC_END_NR].start_address = VMALLOC_END;
 306 #ifdef CONFIG_KFENCE
 307         address_markers[KFENCE_START_NR].start_address = kfence_start;
 308         address_markers[KFENCE_END_NR].start_address = kfence_start + KFENCE_POOL_SIZE;
 309 #endif
 310         sort_address_markers();
 311 #ifdef CONFIG_PTDUMP_DEBUGFS
 312         debugfs_create_file("kernel_page_tables", 0400, NULL, NULL, &ptdump_fops);
 313 #endif /* CONFIG_PTDUMP_DEBUGFS */
 314         return 0;
 315 }
 316 device_initcall(pt_dump_init);