fs/proc/kcore.c

   1 /*
   2  *      fs/proc/kcore.c kernel ELF core dumper
   3  *
   4  *      Modelled on fs/exec.c:aout_core_dump()
   5  *      Jeremy Fitzhardinge <jeremy@sw.oz.au>
   6  *      ELF version written by David Howells <David.Howells@nexor.co.uk>
   7  *      Modified and incorporated into 2.3.x by Tigran Aivazian <tigran@veritas.com>
   8  *      Support to dump vmalloc'd areas (ELF only), Tigran Aivazian <tigran@veritas.com>
   9  *      Safe accesses to vmalloc/direct-mapped discontiguous areas, Kanoj Sarcar <kanoj@sgi.com>
  10  */
  11
  12 #include <linux/mm.h>
  13 #include <linux/proc_fs.h>
  14 #include <linux/user.h>
  15 #include <linux/capability.h>
  16 #include <linux/elf.h>
  17 #include <linux/elfcore.h>
  18 #include <linux/vmalloc.h>
  19 #include <linux/highmem.h>
  20 #include <linux/init.h>
  21 #include <asm/uaccess.h>
  22 #include <asm/io.h>
  23 #include <linux/list.h>
  24
  25 #define CORE_STR "CORE"
  26
  27 #ifndef ELF_CORE_EFLAGS
  28 #define ELF_CORE_EFLAGS 0
  29 #endif
  30
  31 static struct proc_dir_entry *proc_root_kcore;
  32
  33 static int open_kcore(struct inode * inode, struct file * filp)
  34 {
  35         return capable(CAP_SYS_RAWIO) ? 0 : -EPERM;
  36 }
  37
  38 static ssize_t read_kcore(struct file *, char __user *, size_t, loff_t *);
  39
  40 static const struct file_operations proc_kcore_operations = {
  41         .read           = read_kcore,
  42         .open           = open_kcore,
  43 };
  44
  45 #ifndef kc_vaddr_to_offset
  46 #define kc_vaddr_to_offset(v) ((v) - PAGE_OFFSET)
  47 #endif
  48 #ifndef kc_offset_to_vaddr
  49 #define kc_offset_to_vaddr(o) ((o) + PAGE_OFFSET)
  50 #endif
  51
  52 /* An ELF note in memory */
  53 struct memelfnote
  54 {
  55         const char *name;
  56         int type;
  57         unsigned int datasz;
  58         void *data;
  59 };
  60
  61 static LIST_HEAD(kclist_head);
  62 static DEFINE_RWLOCK(kclist_lock);
  63
  64 void
  65 kclist_add(struct kcore_list *new, void *addr, size_t size, int type)
  66 {
  67         new->addr = (unsigned long)addr;
  68         new->size = size;
  69         new->type = type;
  70
  71         write_lock(&kclist_lock);
  72         list_add_tail(&new->list, &kclist_head);
  73         write_unlock(&kclist_lock);
  74 }
  75
  76 static size_t get_kcore_size(int *nphdr, size_t *elf_buflen)
  77 {
  78         size_t try, size;
  79         struct kcore_list *m;
  80
  81         *nphdr = 1; /* PT_NOTE */
  82         size = 0;
  83
  84         list_for_each_entry(m, &kclist_head, list) {
  85                 try = kc_vaddr_to_offset((size_t)m->addr + m->size);
  86                 if (try > size)
  87                         size = try;
  88                 *nphdr = *nphdr + 1;
  89         }
  90         *elf_buflen =   sizeof(struct elfhdr) +
  91                         (*nphdr + 2)*sizeof(struct elf_phdr) +
  92                         3 * ((sizeof(struct elf_note)) +
  93                              roundup(sizeof(CORE_STR), 4)) +
  94                         roundup(sizeof(struct elf_prstatus), 4) +
  95                         roundup(sizeof(struct elf_prpsinfo), 4) +
  96                         roundup(sizeof(struct task_struct), 4);
  97         *elf_buflen = PAGE_ALIGN(*elf_buflen);
  98         return size + *elf_buflen;
  99 }
 100
 101
 102 /*****************************************************************************/
 103 /*
 104  * determine size of ELF note
 105  */
 106 static int notesize(struct memelfnote *en)
 107 {
 108         int sz;
 109
 110         sz = sizeof(struct elf_note);
 111         sz += roundup((strlen(en->name) + 1), 4);
 112         sz += roundup(en->datasz, 4);
 113
 114         return sz;
 115 } /* end notesize() */
 116
 117 /*****************************************************************************/
 118 /*
 119  * store a note in the header buffer
 120  */
 121 static char *storenote(struct memelfnote *men, char *bufp)
 122 {
 123         struct elf_note en;
 124
 125 #define DUMP_WRITE(addr,nr) do { memcpy(bufp,addr,nr); bufp += nr; } while(0)
 126
 127         en.n_namesz = strlen(men->name) + 1;
 128         en.n_descsz = men->datasz;
 129         en.n_type = men->type;
 130
 131         DUMP_WRITE(&en, sizeof(en));
 132         DUMP_WRITE(men->name, en.n_namesz);
 133
 134         /* XXX - cast from long long to long to avoid need for libgcc.a */
 135         bufp = (char*) roundup((unsigned long)bufp,4);
 136         DUMP_WRITE(men->data, men->datasz);
 137         bufp = (char*) roundup((unsigned long)bufp,4);
 138
 139 #undef DUMP_WRITE
 140
 141         return bufp;
 142 } /* end storenote() */
 143
 144 /*
 145  * store an ELF coredump header in the supplied buffer
 146  * nphdr is the number of elf_phdr to insert
 147  */
 148 static void elf_kcore_store_hdr(char *bufp, int nphdr, int dataoff)
 149 {
 150         struct elf_prstatus prstatus;   /* NT_PRSTATUS */
 151         struct elf_prpsinfo prpsinfo;   /* NT_PRPSINFO */
 152         struct elf_phdr *nhdr, *phdr;
 153         struct elfhdr *elf;
 154         struct memelfnote notes[3];
 155         off_t offset = 0;
 156         struct kcore_list *m;
 157
 158         /* setup ELF header */
 159         elf = (struct elfhdr *) bufp;
 160         bufp += sizeof(struct elfhdr);
 161         offset += sizeof(struct elfhdr);
 162         memcpy(elf->e_ident, ELFMAG, SELFMAG);
 163         elf->e_ident[EI_CLASS]  = ELF_CLASS;
 164         elf->e_ident[EI_DATA]   = ELF_DATA;
 165         elf->e_ident[EI_VERSION]= EV_CURRENT;
 166         elf->e_ident[EI_OSABI] = ELF_OSABI;
 167         memset(elf->e_ident+EI_PAD, 0, EI_NIDENT-EI_PAD);
 168         elf->e_type     = ET_CORE;
 169         elf->e_machine  = ELF_ARCH;
 170         elf->e_version  = EV_CURRENT;
 171         elf->e_entry    = 0;
 172         elf->e_phoff    = sizeof(struct elfhdr);
 173         elf->e_shoff    = 0;
 174         elf->e_flags    = ELF_CORE_EFLAGS;
 175         elf->e_ehsize   = sizeof(struct elfhdr);
 176         elf->e_phentsize= sizeof(struct elf_phdr);
 177         elf->e_phnum    = nphdr;
 178         elf->e_shentsize= 0;
 179         elf->e_shnum    = 0;
 180         elf->e_shstrndx = 0;
 181
 182         /* setup ELF PT_NOTE program header */
 183         nhdr = (struct elf_phdr *) bufp;
 184         bufp += sizeof(struct elf_phdr);
 185         offset += sizeof(struct elf_phdr);
 186         nhdr->p_type    = PT_NOTE;
 187         nhdr->p_offset  = 0;
 188         nhdr->p_vaddr   = 0;
 189         nhdr->p_paddr   = 0;
 190         nhdr->p_filesz  = 0;
 191         nhdr->p_memsz   = 0;
 192         nhdr->p_flags   = 0;
 193         nhdr->p_align   = 0;
 194
 195         /* setup ELF PT_LOAD program header for every area */
 196         list_for_each_entry(m, &kclist_head, list) {
 197                 phdr = (struct elf_phdr *) bufp;
 198                 bufp += sizeof(struct elf_phdr);
 199                 offset += sizeof(struct elf_phdr);
 200
 201                 phdr->p_type    = PT_LOAD;
 202                 phdr->p_flags   = PF_R|PF_W|PF_X;
 203                 phdr->p_offset  = kc_vaddr_to_offset(m->addr) + dataoff;
 204                 phdr->p_vaddr   = (size_t)m->addr;
 205                 phdr->p_paddr   = 0;
 206                 phdr->p_filesz  = phdr->p_memsz = m->size;
 207                 phdr->p_align   = PAGE_SIZE;
 208         }
 209
 210         /*
 211          * Set up the notes in similar form to SVR4 core dumps made
 212          * with info from their /proc.
 213          */
 214         nhdr->p_offset  = offset;
 215
 216         /* set up the process status */
 217         notes[0].name = CORE_STR;
 218         notes[0].type = NT_PRSTATUS;
 219         notes[0].datasz = sizeof(struct elf_prstatus);
 220         notes[0].data = &prstatus;
 221
 222         memset(&prstatus, 0, sizeof(struct elf_prstatus));
 223
 224         nhdr->p_filesz  = notesize(&notes[0]);
 225         bufp = storenote(&notes[0], bufp);
 226
 227         /* set up the process info */
 228         notes[1].name   = CORE_STR;
 229         notes[1].type   = NT_PRPSINFO;
 230         notes[1].datasz = sizeof(struct elf_prpsinfo);
 231         notes[1].data   = &prpsinfo;
 232
 233         memset(&prpsinfo, 0, sizeof(struct elf_prpsinfo));
 234         prpsinfo.pr_state       = 0;
 235         prpsinfo.pr_sname       = 'R';
 236         prpsinfo.pr_zomb        = 0;
 237
 238         strcpy(prpsinfo.pr_fname, "vmlinux");
 239         strncpy(prpsinfo.pr_psargs, saved_command_line, ELF_PRARGSZ);
 240
 241         nhdr->p_filesz  += notesize(&notes[1]);
 242         bufp = storenote(&notes[1], bufp);
 243
 244         /* set up the task structure */
 245         notes[2].name   = CORE_STR;
 246         notes[2].type   = NT_TASKSTRUCT;
 247         notes[2].datasz = sizeof(struct task_struct);
 248         notes[2].data   = current;
 249
 250         nhdr->p_filesz  += notesize(&notes[2]);
 251         bufp = storenote(&notes[2], bufp);
 252
 253 } /* end elf_kcore_store_hdr() */
 254
 255 /*****************************************************************************/
 256 /*
 257  * read from the ELF header and then kernel memory
 258  */
 259 static ssize_t
 260 read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)
 261 {
 262         ssize_t acc = 0;
 263         size_t size, tsz;
 264         size_t elf_buflen;
 265         int nphdr;
 266         unsigned long start;
 267
 268         read_lock(&kclist_lock);
 269         proc_root_kcore->size = size = get_kcore_size(&nphdr, &elf_buflen);
 270         if (buflen == 0 || *fpos >= size) {
 271                 read_unlock(&kclist_lock);
 272                 return 0;
 273         }
 274
 275         /* trim buflen to not go beyond EOF */
 276         if (buflen > size - *fpos)
 277                 buflen = size - *fpos;
 278
 279         /* construct an ELF core header if we'll need some of it */
 280         if (*fpos < elf_buflen) {
 281                 char * elf_buf;
 282
 283                 tsz = elf_buflen - *fpos;
 284                 if (buflen < tsz)
 285                         tsz = buflen;
 286                 elf_buf = kzalloc(elf_buflen, GFP_ATOMIC);
 287                 if (!elf_buf) {
 288                         read_unlock(&kclist_lock);
 289                         return -ENOMEM;
 290                 }
 291                 elf_kcore_store_hdr(elf_buf, nphdr, elf_buflen);
 292                 read_unlock(&kclist_lock);
 293                 if (copy_to_user(buffer, elf_buf + *fpos, tsz)) {
 294                         kfree(elf_buf);
 295                         return -EFAULT;
 296                 }
 297                 kfree(elf_buf);
 298                 buflen -= tsz;
 299                 *fpos += tsz;
 300                 buffer += tsz;
 301                 acc += tsz;
 302
 303                 /* leave now if filled buffer already */
 304                 if (buflen == 0)
 305                         return acc;
 306         } else
 307                 read_unlock(&kclist_lock);
 308
 309         /*
 310          * Check to see if our file offset matches with any of
 311          * the addresses in the elf_phdr on our list.
 312          */
 313         start = kc_offset_to_vaddr(*fpos - elf_buflen);
 314         if ((tsz = (PAGE_SIZE - (start & ~PAGE_MASK))) > buflen)
 315                 tsz = buflen;
 316
 317         while (buflen) {
 318                 struct kcore_list *m;
 319
 320                 read_lock(&kclist_lock);
 321                 list_for_each_entry(m, &kclist_head, list) {
 322                         if (start >= m->addr && start < (m->addr+m->size))
 323                                 break;
 324                 }
 325                 read_unlock(&kclist_lock);
 326
 327                 if (m == NULL) {
 328                         if (clear_user(buffer, tsz))
 329                                 return -EFAULT;
 330                 } else if (is_vmalloc_addr((void *)start)) {
 331                         char * elf_buf;
 332
 333                         elf_buf = kzalloc(tsz, GFP_KERNEL);
 334                         if (!elf_buf)
 335                                 return -ENOMEM;
 336                         vread(elf_buf, (char *)start, tsz);
 337                         /* we have to zero-fill user buffer even if no read */
 338                         if (copy_to_user(buffer, elf_buf, tsz)) {
 339                                 kfree(elf_buf);
 340                                 return -EFAULT;
 341                         }
 342                         kfree(elf_buf);
 343                 } else {
 344                         if (kern_addr_valid(start)) {
 345                                 unsigned long n;
 346
 347                                 n = copy_to_user(buffer, (char *)start, tsz);
 348                                 /*
 349                                  * We cannot distingush between fault on source
 350                                  * and fault on destination. When this happens
 351                                  * we clear too and hope it will trigger the
 352                                  * EFAULT again.
 353                                  */
 354                                 if (n) {
 355                                         if (clear_user(buffer + tsz - n,
 356                                                                 n))
 357                                                 return -EFAULT;
 358                                 }
 359                         } else {
 360                                 if (clear_user(buffer, tsz))
 361                                         return -EFAULT;
 362                         }
 363                 }
 364                 buflen -= tsz;
 365                 *fpos += tsz;
 366                 buffer += tsz;
 367                 acc += tsz;
 368                 start += tsz;
 369                 tsz = (buflen > PAGE_SIZE ? PAGE_SIZE : buflen);
 370         }
 371
 372         return acc;
 373 }
 374
 375 static struct kcore_list kcore_vmalloc;
 376
 377 static int __init proc_kcore_init(void)
 378 {
 379         proc_root_kcore = proc_create("kcore", S_IRUSR, NULL, &proc_kcore_operations);
 380
 381         kclist_add(&kcore_vmalloc, (void *)VMALLOC_START,
 382                 VMALLOC_END - VMALLOC_START, KCORE_VMALLOC);
 383         return 0;
 384 }
 385 module_init(proc_kcore_init);