elfops.c

   1 /* The nasty work of reading 32 and 64-bit modules is in here. */
   2 #include <elf.h>
   3 #include <sys/types.h>
   4 #include <unistd.h>
   5 #include <stdlib.h>
   6 #include <string.h>
   7 #include <errno.h>
   8 #include <fcntl.h>
   9 #include "depmod.h"
  10 #include "util.h"
  11 #include "logging.h"
  12 #include "elfops.h"
  13 #include "tables.h"
  14 #include "zlibsupport.h"
  15
  16 #include "testing.h"
  17
  18 /* Symbol types, returned by load_dep_syms */
  19 static const char *weak_sym = "W";
  20 static const char *undef_sym = "U";
  21
  22 /* dump_modversions helper */
  23 static const char *skip_dot(const char *str)
  24 {
  25        /* For our purposes, .foo matches foo.  PPC64 needs this. */
  26        if (str && str[0] == '.')
  27                return str + 1;
  28        return str;
  29 }
  30
  31 #define ELF32BIT
  32 #include "elfops_core.c"
  33 #undef ELF32BIT
  34
  35 #define ELF64BIT
  36 #include "elfops_core.c"
  37 #undef ELF64BIT
  38
  39 /*
  40  * Check ELF file header.
  41  */
  42 static int elf_ident(void *file, unsigned long fsize, int *conv)
  43 {
  44         /* "\177ELF" <byte> where byte = 001 for 32-bit, 002 for 64 */
  45         unsigned char *ident = file;
  46
  47         if (fsize < EI_CLASS || memcmp(file, ELFMAG, SELFMAG) != 0)
  48                 return -ENOEXEC;        /* Not an ELF object */
  49         if (ident[EI_DATA] == 0 || ident[EI_DATA] > 2)
  50                 return -EINVAL;         /* Unknown endianness */
  51
  52         if (conv != NULL)
  53                 *conv = native_endianness() != ident[EI_DATA];
  54         return ident[EI_CLASS];
  55 }
  56
  57 /*
  58  * grab_elf_file - read ELF file into memory
  59  * @pathame: file to load
  60  *
  61  * Returns NULL, and errno set on error.
  62  */
  63 struct elf_file *grab_elf_file(const char *pathname)
  64 {
  65         int fd;
  66         int err;
  67         struct elf_file *file;
  68
  69         fd = open(pathname, O_RDONLY, 0);
  70         if (fd < 0)
  71                 return NULL;
  72         file = grab_elf_file_fd(pathname, fd);
  73
  74         err = errno;
  75         close(fd);
  76         errno = err;
  77         return file;
  78 }
  79
  80 /*
  81  * grab_elf_file_fd - read ELF file from file descriptor into memory
  82  * @pathame: name of file to load
  83  * @fd: file descriptor of file to load
  84  *
  85  * Returns NULL, and errno set on error.
  86  */
  87 struct elf_file *grab_elf_file_fd(const char *pathname, int fd)
  88 {
  89         struct elf_file *file;
  90
  91         file = malloc(sizeof(*file));
  92         if (!file) {
  93                 errno = ENOMEM;
  94                 return NULL;
  95         }
  96         file->pathname = strdup(pathname);
  97         if (!file->pathname) {
  98                 free(file);
  99                 errno = ENOMEM;
 100                 return NULL;
 101         }
 102         file->data = grab_fd(fd, &file->len);
 103         if (!file->data)
 104                 goto fail;
 105
 106         switch (elf_ident(file->data, file->len, &file->conv)) {
 107         case ELFCLASS32:
 108                 file->ops = &mod_ops32;
 109                 break;
 110         case ELFCLASS64:
 111                 file->ops = &mod_ops64;
 112                 break;
 113         case -ENOEXEC: /* Not an ELF object */
 114         case -EINVAL: /* Unknown endianness */
 115         default: /* Unknown word size */
 116                 errno = ENOEXEC;
 117                 goto fail;
 118         }
 119         return file;
 120 fail:
 121         release_elf_file(file);
 122         return NULL;
 123 }
 124
 125 void release_elf_file(struct elf_file *file)
 126 {
 127         int err = errno;
 128
 129         if (!file)
 130                 return;
 131
 132         release_file(file->data, file->len);
 133         free(file->pathname);
 134         free(file);
 135
 136         errno = err;
 137 }