tpm: Simplify creation of cancel path

Simplify the creation of the cancel path given the TPM's device path.
Given the path /dev/tpm0 build the path /sys/class/misc/tpm0/device/cancel.

Signed-off-by: Stefan Berger <stefanb@linux.vnet.ibm.com>

---
 tpm/tpm_passthrough.c |   74 +++++++++++---------------------------------------
 1 file changed, 17 insertions(+), 57 deletions(-)

On 04/15/2013 03:08 PM, Stefan Berger wrote:
> Simplify the creation of the cancel path given the TPM's device path.
> Given the path /dev/tpm0 build the path /sys/class/misc/tpm0/device/cancel.
> 
> Signed-off-by: Stefan Berger <stefanb@linux.vnet.ibm.com>
> 
> ---
>  tpm/tpm_passthrough.c |   74 +++++++++++---------------------------------------
>  1 file changed, 17 insertions(+), 57 deletions(-)

Reviewed-by: Eric Blake <eblake@redhat.com>

and matches a counterpart change you proposed for libvirt.

Stefan Berger <stefanb@linux.vnet.ibm.com> writes:

> Simplify the creation of the cancel path given the TPM's device path.
> Given the path /dev/tpm0 build the path /sys/class/misc/tpm0/device/cancel.
>
> Signed-off-by: Stefan Berger <stefanb@linux.vnet.ibm.com>

No longer applies.  Had you sent with git-send-patch, git am --3way
would have figured it out.  Please use git-send-patch in the future.

Regards,

Anthony Liguori

>
> ---
>  tpm/tpm_passthrough.c |   74 +++++++++++---------------------------------------
>  1 file changed, 17 insertions(+), 57 deletions(-)
>
> Index: qemu-git.pt/tpm/tpm_passthrough.c
> ===================================================================
> --- qemu-git.pt.orig/tpm/tpm_passthrough.c
> +++ qemu-git.pt/tpm/tpm_passthrough.c
> @@ -336,45 +336,17 @@ static int tpm_passthrough_test_tpmdev(i
>  }
>  
>  /*
> - * Check whether the given base path, e.g.,  /sys/class/misc/tpm0/device,
> - * is the sysfs directory of a TPM. A TPM sysfs directory should be uniquely
> - * recognizable by the file entries 'pcrs' and 'cancel'.
> - * Upon success 'true' is returned and the basebath buffer has '/cancel'
> - * appended.
> - */
> -static bool tpm_passthrough_check_sysfs_cancel(char *basepath, size_t bufsz)
> -{
> -    char path[PATH_MAX];
> -    struct stat statbuf;
> -
> -    snprintf(path, sizeof(path), "%s/pcrs", basepath);
> -    if (stat(path, &statbuf) == -1 || !S_ISREG(statbuf.st_mode)) {
> -        return false;
> -    }
> -
> -    snprintf(path, sizeof(path), "%s/cancel", basepath);
> -    if (stat(path, &statbuf) == -1 || !S_ISREG(statbuf.st_mode)) {
> -        return false;
> -    }
> -
> -    strncpy(basepath, path, bufsz);
> -
> -    return true;
> -}
> -
> -/*
>   * Unless path or file descriptor set has been provided by user,
>   * determine the sysfs cancel file following kernel documentation
>   * in Documentation/ABI/stable/sysfs-class-tpm.
> + * From /dev/tpm0 create /sys/class/misc/tpm0/device/cancel
>   */
>  static int tpm_passthrough_open_sysfs_cancel(TPMBackend *tb)
>  {
> +    TPMPassthruState *tpm_pt = TPM_PASSTHROUGH(tb);
>      int fd = -1;
> -    unsigned int idx;
> -    DIR *pnp_dir;
> +    char *dev;
>      char path[PATH_MAX];
> -    struct dirent entry, *result;
> -    int len;
>  
>      if (tb->cancel_path) {
>          fd = qemu_open(tb->cancel_path, O_WRONLY);
> @@ -385,34 +357,22 @@ static int tpm_passthrough_open_sysfs_ca
>          return fd;
>      }
>  
> -    snprintf(path, sizeof(path), "/sys/class/misc");
> -    pnp_dir = opendir(path);
> -    if (pnp_dir != NULL) {
> -        while (readdir_r(pnp_dir, &entry, &result) == 0 &&
> -               result != NULL) {
> -            /*
> -             * only allow /sys/class/misc/tpm%u type of paths
> -             */
> -            if (sscanf(entry.d_name, "tpm%u%n", &idx, &len) < 1 ||
> -                len <= strlen("tpm") ||
> -                len != strlen(entry.d_name)) {
> -                continue;
> -            }
> -
> -            snprintf(path, sizeof(path), "/sys/class/misc/%s/device",
> -                     entry.d_name);
> -            if (!tpm_passthrough_check_sysfs_cancel(path, sizeof(path))) {
> -                continue;
> -            }
> -
> +    dev = strrchr(tpm_pt->tpm_dev, '/');
> +    if (dev) {
> +        dev++;
> +        if (snprintf(path, sizeof(path), "/sys/class/misc/%s/device/cancel",
> +                     dev) < sizeof(path)) {
>              fd = qemu_open(path, O_WRONLY);
> -            break;
> +            if (fd >= 0) {
> +                tb->cancel_path = g_strdup(path);
> +            } else {
> +                error_report("tpm_passthrough: Could not open TPM cancel "
> +                             "path %s : %s", path, strerror(errno));
> +            }
>          }
> -        closedir(pnp_dir);
> -    }
> -
> -    if (fd >= 0) {
> -        tb->cancel_path = g_strdup(path);
> +    } else {
> +       error_report("tpm_passthrough: Bad TPM device path %s",
> +                    tpm_pt->tpm_dev);
>      }
>  
>      return fd;

On 04/16/2013 02:16 PM, Anthony Liguori wrote:
> Stefan Berger <stefanb@linux.vnet.ibm.com> writes:
>
>> Simplify the creation of the cancel path given the TPM's device path.
>> Given the path /dev/tpm0 build the path /sys/class/misc/tpm0/device/cancel.
>>
>> Signed-off-by: Stefan Berger <stefanb@linux.vnet.ibm.com>
> No longer applies.  Had you sent with git-send-patch, git am --3way
> would have figured it out.  Please use git-send-patch in the future.

I reposted it.

http://lists.gnu.org/archive/html/qemu-devel/2013-04/msg03330.html

Stefan