drivers/char/tpm/eventlog/common.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Copyright (C) 2005, 2012 IBM Corporation
   4  *
   5  * Authors:
   6  *      Kent Yoder <key@linux.vnet.ibm.com>
   7  *      Seiji Munetoh <munetoh@jp.ibm.com>
   8  *      Stefan Berger <stefanb@us.ibm.com>
   9  *      Reiner Sailer <sailer@watson.ibm.com>
  10  *      Kylene Hall <kjhall@us.ibm.com>
  11  *      Nayna Jain <nayna@linux.vnet.ibm.com>
  12  *
  13  * Access to the event log created by a system's firmware / BIOS
  14  */
  15
  16 #include <linux/seq_file.h>
  17 #include <linux/fs.h>
  18 #include <linux/security.h>
  19 #include <linux/module.h>
  20 #include <linux/tpm_eventlog.h>
  21
  22 #include "../tpm.h"
  23 #include "common.h"
  24
  25 static int tpm_bios_measurements_open(struct inode *inode,
  26                                             struct file *file)
  27 {
  28         int err;
  29         struct seq_file *seq;
  30         struct tpm_chip_seqops *chip_seqops;
  31         const struct seq_operations *seqops;
  32         struct tpm_chip *chip;
  33
  34         inode_lock(inode);
  35         if (!inode->i_private) {
  36                 inode_unlock(inode);
  37                 return -ENODEV;
  38         }
  39         chip_seqops = (struct tpm_chip_seqops *)inode->i_private;
  40         seqops = chip_seqops->seqops;
  41         chip = chip_seqops->chip;
  42         get_device(&chip->dev);
  43         inode_unlock(inode);
  44
  45         /* now register seq file */
  46         err = seq_open(file, seqops);
  47         if (!err) {
  48                 seq = file->private_data;
  49                 seq->private = chip;
  50         }
  51
  52         return err;
  53 }
  54
  55 static int tpm_bios_measurements_release(struct inode *inode,
  56                                          struct file *file)
  57 {
  58         struct seq_file *seq = (struct seq_file *)file->private_data;
  59         struct tpm_chip *chip = (struct tpm_chip *)seq->private;
  60
  61         put_device(&chip->dev);
  62
  63         return seq_release(inode, file);
  64 }
  65
  66 static const struct file_operations tpm_bios_measurements_ops = {
  67         .owner = THIS_MODULE,
  68         .open = tpm_bios_measurements_open,
  69         .read = seq_read,
  70         .llseek = seq_lseek,
  71         .release = tpm_bios_measurements_release,
  72 };
  73
  74 static int tpm_read_log(struct tpm_chip *chip)
  75 {
  76         int rc;
  77
  78         if (chip->log.bios_event_log != NULL) {
  79                 dev_dbg(&chip->dev,
  80                         "%s: ERROR - event log already initialized\n",
  81                         __func__);
  82                 return -EFAULT;
  83         }
  84
  85         rc = tpm_read_log_acpi(chip);
  86         if (rc != -ENODEV)
  87                 return rc;
  88
  89         rc = tpm_read_log_efi(chip);
  90         if (rc != -ENODEV)
  91                 return rc;
  92
  93         return tpm_read_log_of(chip);
  94 }
  95
  96 /*
  97  * tpm_bios_log_setup() - Read the event log from the firmware
  98  * @chip: TPM chip to use.
  99  *
 100  * If an event log is found then the securityfs files are setup to
 101  * export it to userspace, otherwise nothing is done.
 102  *
 103  * Returns -ENODEV if the firmware has no event log or securityfs is not
 104  * supported.
 105  */
 106 int tpm_bios_log_setup(struct tpm_chip *chip)
 107 {
 108         const char *name = dev_name(&chip->dev);
 109         unsigned int cnt;
 110         int log_version;
 111         int rc = 0;
 112
 113         rc = tpm_read_log(chip);
 114         if (rc < 0)
 115                 return rc;
 116         log_version = rc;
 117
 118         cnt = 0;
 119         chip->bios_dir[cnt] = securityfs_create_dir(name, NULL);
 120         /* NOTE: securityfs_create_dir can return ENODEV if securityfs is
 121          * compiled out. The caller should ignore the ENODEV return code.
 122          */
 123         if (IS_ERR(chip->bios_dir[cnt]))
 124                 goto err;
 125         cnt++;
 126
 127         chip->bin_log_seqops.chip = chip;
 128         if (log_version == EFI_TCG2_EVENT_LOG_FORMAT_TCG_2)
 129                 chip->bin_log_seqops.seqops =
 130                         &tpm2_binary_b_measurements_seqops;
 131         else
 132                 chip->bin_log_seqops.seqops =
 133                         &tpm1_binary_b_measurements_seqops;
 134
 135
 136         chip->bios_dir[cnt] =
 137             securityfs_create_file("binary_bios_measurements",
 138                                    0440, chip->bios_dir[0],
 139                                    (void *)&chip->bin_log_seqops,
 140                                    &tpm_bios_measurements_ops);
 141         if (IS_ERR(chip->bios_dir[cnt]))
 142                 goto err;
 143         cnt++;
 144
 145         if (!(chip->flags & TPM_CHIP_FLAG_TPM2)) {
 146
 147                 chip->ascii_log_seqops.chip = chip;
 148                 chip->ascii_log_seqops.seqops =
 149                         &tpm1_ascii_b_measurements_seqops;
 150
 151                 chip->bios_dir[cnt] =
 152                         securityfs_create_file("ascii_bios_measurements",
 153                                                0440, chip->bios_dir[0],
 154                                                (void *)&chip->ascii_log_seqops,
 155                                                &tpm_bios_measurements_ops);
 156                 if (IS_ERR(chip->bios_dir[cnt]))
 157                         goto err;
 158                 cnt++;
 159         }
 160
 161         return 0;
 162
 163 err:
 164         rc = PTR_ERR(chip->bios_dir[cnt]);
 165         chip->bios_dir[cnt] = NULL;
 166         tpm_bios_log_teardown(chip);
 167         return rc;
 168 }
 169
 170 void tpm_bios_log_teardown(struct tpm_chip *chip)
 171 {
 172         int i;
 173         struct inode *inode;
 174
 175         /* securityfs_remove currently doesn't take care of handling sync
 176          * between removal and opening of pseudo files. To handle this, a
 177          * workaround is added by making i_private = NULL here during removal
 178          * and to check it during open(), both within inode_lock()/unlock().
 179          * This design ensures that open() either safely gets kref or fails.
 180          */
 181         for (i = (TPM_NUM_EVENT_LOG_FILES - 1); i >= 0; i--) {
 182                 if (chip->bios_dir[i]) {
 183                         inode = d_inode(chip->bios_dir[i]);
 184                         inode_lock(inode);
 185                         inode->i_private = NULL;
 186                         inode_unlock(inode);
 187                         securityfs_remove(chip->bios_dir[i]);
 188                 }
 189         }
 190 }