arch/riscv/mm/ptdump.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (C) 2019 SiFive
   4  */
   5
   6 #include <linux/init.h>
   7 #include <linux/debugfs.h>
   8 #include <linux/seq_file.h>
   9 #include <linux/ptdump.h>
  10
  11 #include <asm/ptdump.h>
  12 #include <asm/pgtable.h>
  13 #include <asm/kasan.h>
  14
  15 #define pt_dump_seq_printf(m, fmt, args...)     \
  16 ({                                              \
  17         if (m)                                  \
  18                 seq_printf(m, fmt, ##args);     \
  19 })
  20
  21 #define pt_dump_seq_puts(m, fmt)        \
  22 ({                                      \
  23         if (m)                          \
  24                 seq_printf(m, fmt);     \
  25 })
  26
  27 /*
  28  * The page dumper groups page table entries of the same type into a single
  29  * description. It uses pg_state to track the range information while
  30  * iterating over the pte entries. When the continuity is broken it then
  31  * dumps out a description of the range.
  32  */
  33 struct pg_state {
  34         struct ptdump_state ptdump;
  35         struct seq_file *seq;
  36         const struct addr_marker *marker;
  37         unsigned long start_address;
  38         unsigned long start_pa;
  39         unsigned long last_pa;
  40         int level;
  41         u64 current_prot;
  42         bool check_wx;
  43         unsigned long wx_pages;
  44 };
  45
  46 /* Address marker */
  47 struct addr_marker {
  48         unsigned long start_address;
  49         const char *name;
  50 };
  51
  52 static struct addr_marker address_markers[] = {
  53 #ifdef CONFIG_KASAN
  54         {KASAN_SHADOW_START,    "Kasan shadow start"},
  55         {KASAN_SHADOW_END,      "Kasan shadow end"},
  56 #endif
  57         {FIXADDR_START,         "Fixmap start"},
  58         {FIXADDR_TOP,           "Fixmap end"},
  59         {PCI_IO_START,          "PCI I/O start"},
  60         {PCI_IO_END,            "PCI I/O end"},
  61 #ifdef CONFIG_SPARSEMEM_VMEMMAP
  62         {VMEMMAP_START,         "vmemmap start"},
  63         {VMEMMAP_END,           "vmemmap end"},
  64 #endif
  65         {VMALLOC_START,         "vmalloc() area"},
  66         {VMALLOC_END,           "vmalloc() end"},
  67         {PAGE_OFFSET,           "Linear mapping"},
  68         {-1, NULL},
  69 };
  70
  71 /* Page Table Entry */
  72 struct prot_bits {
  73         u64 mask;
  74         u64 val;
  75         const char *set;
  76         const char *clear;
  77 };
  78
  79 static const struct prot_bits pte_bits[] = {
  80         {
  81                 .mask = _PAGE_SOFT,
  82                 .val = _PAGE_SOFT,
  83                 .set = "RSW",
  84                 .clear = "   ",
  85         }, {
  86                 .mask = _PAGE_DIRTY,
  87                 .val = _PAGE_DIRTY,
  88                 .set = "D",
  89                 .clear = ".",
  90         }, {
  91                 .mask = _PAGE_ACCESSED,
  92                 .val = _PAGE_ACCESSED,
  93                 .set = "A",
  94                 .clear = ".",
  95         }, {
  96                 .mask = _PAGE_GLOBAL,
  97                 .val = _PAGE_GLOBAL,
  98                 .set = "G",
  99                 .clear = ".",
 100         }, {
 101                 .mask = _PAGE_USER,
 102                 .val = _PAGE_USER,
 103                 .set = "U",
 104                 .clear = ".",
 105         }, {
 106                 .mask = _PAGE_EXEC,
 107                 .val = _PAGE_EXEC,
 108                 .set = "X",
 109                 .clear = ".",
 110         }, {
 111                 .mask = _PAGE_WRITE,
 112                 .val = _PAGE_WRITE,
 113                 .set = "W",
 114                 .clear = ".",
 115         }, {
 116                 .mask = _PAGE_READ,
 117                 .val = _PAGE_READ,
 118                 .set = "R",
 119                 .clear = ".",
 120         }, {
 121                 .mask = _PAGE_PRESENT,
 122                 .val = _PAGE_PRESENT,
 123                 .set = "V",
 124                 .clear = ".",
 125         }
 126 };
 127
 128 /* Page Level */
 129 struct pg_level {
 130         const char *name;
 131         u64 mask;
 132 };
 133
 134 static struct pg_level pg_level[] = {
 135         { /* pgd */
 136                 .name = "PGD",
 137         }, { /* p4d */
 138                 .name = (CONFIG_PGTABLE_LEVELS > 4) ? "P4D" : "PGD",
 139         }, { /* pud */
 140                 .name = (CONFIG_PGTABLE_LEVELS > 3) ? "PUD" : "PGD",
 141         }, { /* pmd */
 142                 .name = (CONFIG_PGTABLE_LEVELS > 2) ? "PMD" : "PGD",
 143         }, { /* pte */
 144                 .name = "PTE",
 145         },
 146 };
 147
 148 static void dump_prot(struct pg_state *st)
 149 {
 150         unsigned int i;
 151
 152         for (i = 0; i < ARRAY_SIZE(pte_bits); i++) {
 153                 const char *s;
 154
 155                 if ((st->current_prot & pte_bits[i].mask) == pte_bits[i].val)
 156                         s = pte_bits[i].set;
 157                 else
 158                         s = pte_bits[i].clear;
 159
 160                 if (s)
 161                         pt_dump_seq_printf(st->seq, " %s", s);
 162         }
 163 }
 164
 165 #ifdef CONFIG_64BIT
 166 #define ADDR_FORMAT     "0x%016lx"
 167 #else
 168 #define ADDR_FORMAT     "0x%08lx"
 169 #endif
 170 static void dump_addr(struct pg_state *st, unsigned long addr)
 171 {
 172         static const char units[] = "KMGTPE";
 173         const char *unit = units;
 174         unsigned long delta;
 175
 176         pt_dump_seq_printf(st->seq, ADDR_FORMAT "-" ADDR_FORMAT "   ",
 177                            st->start_address, addr);
 178
 179         pt_dump_seq_printf(st->seq, " " ADDR_FORMAT " ", st->start_pa);
 180         delta = (addr - st->start_address) >> 10;
 181
 182         while (!(delta & 1023) && unit[1]) {
 183                 delta >>= 10;
 184                 unit++;
 185         }
 186
 187         pt_dump_seq_printf(st->seq, "%9lu%c %s", delta, *unit,
 188                            pg_level[st->level].name);
 189 }
 190
 191 static void note_prot_wx(struct pg_state *st, unsigned long addr)
 192 {
 193         if (!st->check_wx)
 194                 return;
 195
 196         if ((st->current_prot & (_PAGE_WRITE | _PAGE_EXEC)) !=
 197             (_PAGE_WRITE | _PAGE_EXEC))
 198                 return;
 199
 200         WARN_ONCE(1, "riscv/mm: Found insecure W+X mapping at address %p/%pS\n",
 201                   (void *)st->start_address, (void *)st->start_address);
 202
 203         st->wx_pages += (addr - st->start_address) / PAGE_SIZE;
 204 }
 205
 206 static void note_page(struct ptdump_state *pt_st, unsigned long addr,
 207                       int level, unsigned long val)
 208 {
 209         struct pg_state *st = container_of(pt_st, struct pg_state, ptdump);
 210         u64 pa = PFN_PHYS(pte_pfn(__pte(val)));
 211         u64 prot = 0;
 212
 213         if (level >= 0)
 214                 prot = val & pg_level[level].mask;
 215
 216         if (st->level == -1) {
 217                 st->level = level;
 218                 st->current_prot = prot;
 219                 st->start_address = addr;
 220                 st->start_pa = pa;
 221                 st->last_pa = pa;
 222                 pt_dump_seq_printf(st->seq, "---[ %s ]---\n", st->marker->name);
 223         } else if (prot != st->current_prot ||
 224                    level != st->level || addr >= st->marker[1].start_address) {
 225                 if (st->current_prot) {
 226                         note_prot_wx(st, addr);
 227                         dump_addr(st, addr);
 228                         dump_prot(st);
 229                         pt_dump_seq_puts(st->seq, "\n");
 230                 }
 231
 232                 while (addr >= st->marker[1].start_address) {
 233                         st->marker++;
 234                         pt_dump_seq_printf(st->seq, "---[ %s ]---\n",
 235                                            st->marker->name);
 236                 }
 237
 238                 st->start_address = addr;
 239                 st->start_pa = pa;
 240                 st->last_pa = pa;
 241                 st->current_prot = prot;
 242                 st->level = level;
 243         } else {
 244                 st->last_pa = pa;
 245         }
 246 }
 247
 248 static void ptdump_walk(struct seq_file *s)
 249 {
 250         struct pg_state st = {
 251                 .seq = s,
 252                 .marker = address_markers,
 253                 .level = -1,
 254                 .ptdump = {
 255                         .note_page = note_page,
 256                         .range = (struct ptdump_range[]) {
 257                                 {KERN_VIRT_START, ULONG_MAX},
 258                                 {0, 0}
 259                         }
 260                 }
 261         };
 262
 263         ptdump_walk_pgd(&st.ptdump, &init_mm, NULL);
 264 }
 265
 266 void ptdump_check_wx(void)
 267 {
 268         struct pg_state st = {
 269                 .seq = NULL,
 270                 .marker = (struct addr_marker[]) {
 271                         {0, NULL},
 272                         {-1, NULL},
 273                 },
 274                 .level = -1,
 275                 .check_wx = true,
 276                 .ptdump = {
 277                         .note_page = note_page,
 278                         .range = (struct ptdump_range[]) {
 279                                 {KERN_VIRT_START, ULONG_MAX},
 280                                 {0, 0}
 281                         }
 282                 }
 283         };
 284
 285         ptdump_walk_pgd(&st.ptdump, &init_mm, NULL);
 286
 287         if (st.wx_pages)
 288                 pr_warn("Checked W+X mappings: failed, %lu W+X pages found\n",
 289                         st.wx_pages);
 290         else
 291                 pr_info("Checked W+X mappings: passed, no W+X pages found\n");
 292 }
 293
 294 static int ptdump_show(struct seq_file *m, void *v)
 295 {
 296         ptdump_walk(m);
 297
 298         return 0;
 299 }
 300
 301 DEFINE_SHOW_ATTRIBUTE(ptdump);
 302
 303 static int ptdump_init(void)
 304 {
 305         unsigned int i, j;
 306
 307         for (i = 0; i < ARRAY_SIZE(pg_level); i++)
 308                 for (j = 0; j < ARRAY_SIZE(pte_bits); j++)
 309                         pg_level[i].mask |= pte_bits[j].mask;
 310
 311         debugfs_create_file("kernel_page_tables", 0400, NULL, NULL,
 312                             &ptdump_fops);
 313
 314         return 0;
 315 }
 316
 317 device_initcall(ptdump_init);