libkmod/libkmod-file.c

   1 /*
   2  * libkmod - interface to kernel module operations
   3  *
   4  * Copyright (C) 2011  ProFUSION embedded systems
   5  *
   6  * This library is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU Lesser General Public
   8  * License as published by the Free Software Foundation; either
   9  * version 2.1 of the License, or (at your option) any later version.
  10  *
  11  * This library is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public
  17  * License along with this library; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  19  */
  20
  21 #include <stdio.h>
  22 #include <stdlib.h>
  23 #include <errno.h>
  24 #include <string.h>
  25 #include <sys/types.h>
  26 #include <sys/stat.h>
  27 #include <sys/mman.h>
  28 #include <unistd.h>
  29
  30 #include "libkmod.h"
  31 #include "libkmod-private.h"
  32
  33 #ifdef ENABLE_ZLIB
  34 #include <zlib.h>
  35 #endif
  36
  37 struct kmod_file {
  38 #ifdef ENABLE_ZLIB
  39         gzFile gzf;
  40 #endif
  41         int fd;
  42         off_t size;
  43         void *memory;
  44 };
  45
  46 #ifdef ENABLE_ZLIB
  47 #define READ_STEP (4 * 1024 * 1024)
  48
  49 static bool check_zlib(struct kmod_file *file)
  50 {
  51         uint8_t magic[2] = {0, 0}, zlibmagic[2] = {0x1f, 0x8b};
  52         size_t done = 0, todo = 2;
  53         while (todo > 0) {
  54                 ssize_t r = read(file->fd, magic + done, todo);
  55                 if (r > 0){
  56                         todo -= r;
  57                         done += r;
  58                 } else if (r == 0)
  59                         goto error;
  60                 else if (errno == EAGAIN || errno == EINTR)
  61                         continue;
  62                 else
  63                         goto error;
  64         }
  65         lseek(file->fd, 0, SEEK_SET);
  66         return memcmp(magic, zlibmagic, 2) == 0;
  67 error:
  68         lseek(file->fd, 0, SEEK_SET);
  69         return false;
  70 }
  71
  72 static int zlib_file_open(struct kmod_file *file)
  73 {
  74         int err = 0;
  75         off_t did = 0, total = 0;
  76         unsigned char *p = NULL;
  77
  78         errno = 0;
  79         file->gzf = gzdopen(file->fd, "rb");
  80         if (file->gzf == NULL) {
  81                 close(file->fd);
  82                 return -errno;
  83         }
  84
  85         for (;;) {
  86                 int r;
  87
  88                 if (did == total) {
  89                         void *tmp = realloc(p, total + READ_STEP);
  90                         if (tmp == NULL) {
  91                                 err = -errno;
  92                                 goto error;
  93                         }
  94                         total += READ_STEP;
  95                         p = tmp;
  96                 }
  97
  98                 r = gzread(file->gzf, p + did, total - did);
  99                 if (r == 0)
 100                         break;
 101                 else if (r < 0) {
 102                         err = -errno;
 103                         goto error;
 104                 }
 105                 did += r;
 106         }
 107
 108         file->memory = p;
 109         file->size = did;
 110         return 0;
 111 error:
 112         free(p);
 113         gzclose(file->gzf);
 114         return err;
 115 }
 116 #endif
 117
 118 static int reg_file_open(struct kmod_file *file)
 119 {
 120         struct stat st;
 121         int err = 0;
 122
 123         if (fstat(file->fd, &st) < 0) {
 124                 err = -errno;
 125                 goto error;
 126         }
 127
 128         file->size = st.st_size;
 129         file->memory = mmap(0, file->size, PROT_READ, MAP_PRIVATE, file->fd, 0);
 130         if (file->memory == MAP_FAILED) {
 131                 err = -errno;
 132                 goto error;
 133         }
 134
 135         return 0;
 136 error:
 137         close(file->fd);
 138         return err;
 139 }
 140
 141 struct kmod_file *kmod_file_open(const char *filename)
 142 {
 143         struct kmod_file *file = calloc(1, sizeof(struct kmod_file));
 144         int err;
 145
 146         if (file == NULL)
 147                 return NULL;
 148
 149         file->fd = open(filename, O_RDONLY|O_CLOEXEC);
 150         if (file->fd < 0) {
 151                 err = -errno;
 152                 goto error;
 153         }
 154
 155 #ifdef ENABLE_ZLIB
 156         if (check_zlib(file))
 157                 err = zlib_file_open(file);
 158         else
 159 #endif
 160                 err = reg_file_open(file);
 161
 162 error:
 163         if (err < 0) {
 164                 free(file);
 165                 errno = -err;
 166                 return NULL;
 167         }
 168
 169         return file;
 170 }
 171
 172 void *kmod_file_get_contents(const struct kmod_file *file)
 173 {
 174         return file->memory;
 175 }
 176
 177 off_t kmod_file_get_size(const struct kmod_file *file)
 178 {
 179         return file->size;
 180 }
 181
 182 void kmod_file_unref(struct kmod_file *file)
 183 {
 184 #ifdef ENABLE_ZLIB
 185         if (file->gzf != NULL) {
 186                 free(file->memory);
 187                 gzclose(file->gzf);
 188         } else {
 189 #endif
 190                 munmap(file->memory, file->size);
 191                 close(file->fd);
 192 #ifdef ENABLE_ZLIB
 193         }
 194 #endif
 195         free(file);
 196 }