tpm: expose spaces via a device link /dev/tpmrm<n>

Currently the tpm spaces are not exposed to userspace.  Make this
exposure via a separate device, which can now be opened multiple times
because each read/write transaction goes separately via the space.

Concurrency is protected by the chip->tpm_mutex for each read/write
transaction separately.  The TPM is cleared of all transient objects
by the time the mutex is dropped, so there should be no interference
between the kernel and userspace.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Tested-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>

1 files changed, 65 insertions, 0 deletions

diff --git a/drivers/char/tpm/tpmrm-dev.c b/drivers/char/tpm/tpmrm-dev.c
new file mode 100644
index 000000000000..630bddce65a8
--- /dev/null
+++ b/drivers/char/tpm/tpmrm-dev.c
@@ -0,0 +1,65 @@
+/*
+ * Copyright (C) 2017 James.Bottomley@HansenPartnership.com
+ *
+ * GPLv2
+ */
+#include <linux/slab.h>
+#include "tpm-dev.h"
+
+struct tpmrm_priv {
+	struct file_priv priv;
+	struct tpm_space space;
+};
+
+static int tpmrm_open(struct inode *inode, struct file *file)
+{
+	struct tpm_chip *chip;
+	struct tpmrm_priv *priv;
+	int rc;
+
+	chip = container_of(inode->i_cdev, struct tpm_chip, cdevs);
+	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
+	if (priv == NULL)
+		return -ENOMEM;
+
+	rc = tpm2_init_space(&priv->space);
+	if (rc) {
+		kfree(priv);
+		return -ENOMEM;
+	}
+
+	tpm_common_open(file, chip, &priv->priv);
+
+	return 0;
+}
+
+static int tpmrm_release(struct inode *inode, struct file *file)
+{
+	struct file_priv *fpriv = file->private_data;
+	struct tpmrm_priv *priv = container_of(fpriv, struct tpmrm_priv, priv);
+
+	tpm_common_release(file, fpriv);
+	tpm2_del_space(&priv->space);
+	kfree(priv);
+
+	return 0;
+}
+
+ssize_t tpmrm_write(struct file *file, const char __user *buf,
+		   size_t size, loff_t *off)
+{
+	struct file_priv *fpriv = file->private_data;
+	struct tpmrm_priv *priv = container_of(fpriv, struct tpmrm_priv, priv);
+
+	return tpm_common_write(file, buf, size, off, &priv->space);
+}
+
+const struct file_operations tpmrm_fops = {
+	.owner = THIS_MODULE,
+	.llseek = no_llseek,
+	.open = tpmrm_open,
+	.read = tpm_common_read,
+	.write = tpmrm_write,
+	.release = tpmrm_release,
+};
+