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Re: [Qemu-devel] [PATCH 1/2] nvram: Add TPM NVRAM implementation
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From: |
Corey Bryant |
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Subject: |
Re: [Qemu-devel] [PATCH 1/2] nvram: Add TPM NVRAM implementation |
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Date: |
Wed, 05 Jun 2013 09:28:32 -0400 |
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User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130514 Thunderbird/17.0.6 |
Thanks for reviewing!
On 06/05/2013 05:05 AM, Stefan Hajnoczi wrote:
On Tue, Jun 04, 2013 at 02:18:40PM -0400, Corey Bryant wrote:
Provides TPM NVRAM implementation that enables storing of TPM
NVRAM data in a persistent image file. The block driver is
used to read/write the drive image. This will enable, for
example, an ecrypted QCOW2 image to be used to store sensitive
keys.
This patch provides APIs that a TPM backend can use to read and
write data.
Signed-off-by: Corey Bryant <address@hidden>
---
hw/tpm/Makefile.objs | 1 +
hw/tpm/tpm_nvram.c | 399 ++++++++++++++++++++++++++++++++++++++++++++++++++
hw/tpm/tpm_nvram.h | 25 +++
3 files changed, 425 insertions(+), 0 deletions(-)
create mode 100644 hw/tpm/tpm_nvram.c
create mode 100644 hw/tpm/tpm_nvram.h
diff --git a/hw/tpm/Makefile.objs b/hw/tpm/Makefile.objs
index 99f5983..49faef4 100644
--- a/hw/tpm/Makefile.objs
+++ b/hw/tpm/Makefile.objs
@@ -1,2 +1,3 @@
common-obj-$(CONFIG_TPM_TIS) += tpm_tis.o
+common-obj-$(CONFIG_TPM_TIS) += tpm_nvram.o
common-obj-$(CONFIG_TPM_PASSTHROUGH) += tpm_passthrough.o
diff --git a/hw/tpm/tpm_nvram.c b/hw/tpm/tpm_nvram.c
new file mode 100644
index 0000000..95ff396
--- /dev/null
+++ b/hw/tpm/tpm_nvram.c
@@ -0,0 +1,399 @@
+/*
+ * TPM NVRAM - enables storage of persistent NVRAM data on an image file
+ *
+ * Copyright (C) 2013 IBM Corporation
+ *
+ * Authors:
+ * Stefan Berger <address@hidden>
+ * Corey Bryant <address@hidden>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include "tpm_nvram.h"
+#include "block/block_int.h"
+#include "qemu/thread.h"
+#include "sysemu/sysemu.h"
+
+/* #define TPM_NVRAM_DEBUG */
+
+#ifdef TPM_NVRAM_DEBUG
+#define DPRINTF(fmt, ...) \
+ do { fprintf(stderr, fmt, ## __VA_ARGS__); } while (0)
+#else
+#define DPRINTF(fmt, ...) \
+ do { } while (0)
+#endif
I suggest:
#define TPM_NVRAM_DEBUG 0
#define DPRINTF(fmt, ...) \
do { \
if (TPM_NVRAM_DEBUG) { \
fprintf(stderr, fmt, ## __VA_ARGS__); \
} \
} while (0)
This approach prevents bitrot since the compiler always parses the
printf() whether TPM_NVRAM_DEBUG is 0 or 1. If you #ifdef out the code
completely, like above, then you don't notice compiler warnings/errors
until you actually #define TPM_NVRAM_DEBUG (i.e. prone to bitrot).
Ok
+
+/* Round a value up to the next SIZE */
+#define ROUNDUP(VAL, SIZE) \
+ (((VAL)+(SIZE)-1) & ~((SIZE)-1))
Please drop this macro and use include/qemu/osdep.h:ROUND_UP()
Ok
+
+/* Get the number of sectors required to contain SIZE bytes */
+#define NUM_SECTORS(SIZE) \
+ (ROUNDUP(SIZE, BDRV_SECTOR_SIZE) / BDRV_SECTOR_SIZE)
Please drop this macro and use include/qemu/osdep.h:DIV_ROUND_UP() instead.
Ok
+
+/* Read/write request data */
+typedef struct TPMNvramRWRequest {
+ BlockDriverState *bdrv;
+ bool is_write;
+ uint64_t sector_num;
+ int num_sectors;
+ uint8_t **blob_r;
+ uint8_t *blob_w;
+ uint32_t size;
+ QEMUIOVector *qiov;
+ bool done;
+ int rc;
+
+ QemuMutex completion_mutex;
+ QemuCond completion;
+
+ QSIMPLEQ_ENTRY(TPMNvramRWRequest) list;
+} TPMNvramRWRequest;
+
+/* Mutex protected queue of read/write requests */
+static QemuMutex tpm_nvram_rwrequests_mutex;
+static QSIMPLEQ_HEAD(, TPMNvramRWRequest) tpm_nvram_rwrequests =
+ QSIMPLEQ_HEAD_INITIALIZER(tpm_nvram_rwrequests);
+
+static QEMUBH *tpm_nvram_bh;
+
+/*
+ * Increase the drive size if it's too small to store the blob
+ */
+static int tpm_nvram_adjust_size(BlockDriverState *bdrv, uint64_t sector_num,
+ int num_sectors)
+{
+ int rc = 0;
+ int64_t drive_size, required_size;
+
+ drive_size = bdrv_getlength(bdrv);
+ if (drive_size < 0) {
+ DPRINTF("%s: Unable to determine TPM NVRAM drive size\n", __func__);
+ rc = drive_size;
+ goto err_exit;
+ }
+
+ required_size = (sector_num + num_sectors) * BDRV_SECTOR_SIZE;
+
+ if (drive_size < required_size) {
+ rc = bdrv_truncate(bdrv, required_size);
+ if (rc < 0) {
+ DPRINTF("%s: TPM NVRAM drive too small\n", __func__);
+ }
+ }
+
+err_exit:
+ return rc;
+}
+
+/*
+ * Coroutine that reads a blob from the drive asynchronously
+ */
+static void coroutine_fn tpm_nvram_co_read(void *opaque)
+{
+ TPMNvramRWRequest *rwr = opaque;
+
+ rwr->rc = bdrv_co_readv(rwr->bdrv,
+ rwr->sector_num,
+ rwr->num_sectors,
+ rwr->qiov);
+ rwr->done = true;
+}
+
+/*
+ * Coroutine that writes a blob to the drive asynchronously
+ */
+static void coroutine_fn tpm_nvram_co_write(void *opaque)
+{
+ TPMNvramRWRequest *rwr = opaque;
+
+ rwr->rc = bdrv_co_writev(rwr->bdrv,
+ rwr->sector_num,
+ rwr->num_sectors,
+ rwr->qiov);
+ rwr->done = true;
+}
+
+/*
+ * Prepare for and enter a coroutine to read a blob from the drive
+ */
+static void epm_nvram_do_co_read(TPMNvramRWRequest *rwr)
+{
+ Coroutine *co;
+ size_t buf_len = rwr->num_sectors * BDRV_SECTOR_SIZE;
+ uint8_t *buf = g_malloc(buf_len);
+
+ memset(buf, 0x0, buf_len);
+
+ struct iovec iov = {
+ .iov_base = (void *)buf,
+ .iov_len = rwr->size,
+ };
+
+ qemu_iovec_init_external(rwr->qiov, &iov, 1);
+
+ co = qemu_coroutine_create(tpm_nvram_co_read);
+ qemu_coroutine_enter(co, rwr);
+
+ while (!rwr->done) {
+ qemu_aio_wait();
+ }
The qemu_aio_wait() loop makes this function synchronous - it will block
the current thread until the request completes.
You need to use bdrv_aio_readv()/bdrv_aio_writev() or let the
tpm_nvram_co_read()/tpm_nvram_co_write() coroutine perform the
completion code path instead of waiting for it here.
Ok, I think I can just have the coroutine perform the completion path.
+
+ if (rwr->rc == 0) {
+ rwr->rc = rwr->num_sectors;
+ *rwr->blob_r = g_malloc(rwr->size);
+ memcpy(*rwr->blob_r, buf, rwr->size);
Use bdrv_pread()/bdrv_pwrite() for byte-granularity I/O instead of
duplicating the buffering yourself.
Aren't bdrv_pread()/bdrv_pwrite() synchronous? Wouldn't using them
block the main QEMU thread? That is why I switched to using the
coroutine versions.
+ } else {
+ *rwr->blob_r = NULL;
+ }
+
+ g_free(buf);
+}
+
+/*
+ * Prepare for and enter a coroutine to write a blob to the drive
+ */
+static void tpm_nvram_do_co_write(TPMNvramRWRequest *rwr)
+{
+ Coroutine *co;
+ size_t buf_len = rwr->num_sectors * BDRV_SECTOR_SIZE;
+ uint8_t *buf = g_malloc(buf_len);
+
+ memset(buf, 0x0, buf_len);
+ memcpy(buf, rwr->blob_w, rwr->size);
+
+ struct iovec iov = {
+ .iov_base = (void *)buf,
+ .iov_len = rwr->size,
+ };
+
+ qemu_iovec_init_external(rwr->qiov, &iov, 1);
+
+ rwr->rc = tpm_nvram_adjust_size(rwr->bdrv, rwr->sector_num,
+ rwr->num_sectors);
+ if (rwr->rc < 0) {
+ goto err_exit;
+ }
+
+ co = qemu_coroutine_create(tpm_nvram_co_write);
+ qemu_coroutine_enter(co, rwr);
+
+ while (!rwr->done) {
+ qemu_aio_wait();
+ }
+
+ if (rwr->rc == 0) {
+ rwr->rc = rwr->num_sectors;
+ }
+
+err_exit:
+ g_free(buf);
+}
+
+/*
+ * Initialization for read requests
+ */
+static TPMNvramRWRequest *tpm_nvram_rwrequest_init_read(BlockDriverState *bdrv,
+ int64_t sector_num,
+ uint8_t **blob,
+ uint32_t size)
+{
+ TPMNvramRWRequest *rwr;
+
+ rwr = g_new0(TPMNvramRWRequest, 1);
+ rwr->bdrv = bdrv;
+ rwr->is_write = false;
+ rwr->sector_num = sector_num;
+ rwr->num_sectors = NUM_SECTORS(size);
+ rwr->blob_r = blob;
+ rwr->size = size;
+ rwr->qiov = g_new0(QEMUIOVector, 1);
Why allocate qiov on the heap instead of making it a TPMNvramRWRequest field?
No reason, I'll change that.
+ rwr->done = false;
+
+ return rwr;
+}
+
+/*
+ * Initialization for write requests
+ */
+static TPMNvramRWRequest *tpm_nvram_rwrequest_init_write(BlockDriverState
*bdrv,
+ int64_t sector_num,
+ uint8_t *blob,
+ uint32_t size)
+{
+ TPMNvramRWRequest *rwr;
+
+ rwr = g_new0(TPMNvramRWRequest, 1);
+ rwr->bdrv = bdrv;
+ rwr->is_write = true;
+ rwr->sector_num = sector_num;
+ rwr->num_sectors = NUM_SECTORS(size);
+ rwr->blob_w = blob;
+ rwr->size = size;
+ rwr->qiov = g_new0(QEMUIOVector, 1);
+ rwr->done = false;
+
+ return rwr;
+}
+
+/*
+ * Free read/write request memory
+ */
+static void tpm_nvram_rwrequest_free(TPMNvramRWRequest *rwr)
+{
+ g_free(rwr->qiov);
+ g_free(rwr);
+}
+
+/*
+ * Execute a read or write of TPM NVRAM blob data
+ */
+static void tpm_nvram_rwrequest_exec(TPMNvramRWRequest *rwr)
+{
+ if (rwr->is_write) {
+ tpm_nvram_do_co_write(rwr);
+ } else {
+ tpm_nvram_do_co_read(rwr);
+ }
+
+ qemu_mutex_lock(&rwr->completion_mutex);
+ qemu_cond_signal(&rwr->completion);
+ qemu_mutex_unlock(&rwr->completion_mutex);
+}
+
+/*
+ * Bottom-half callback that is invoked by QEMU's main thread to
+ * process TPM NVRAM read/write requests.
+ */
+static void tpm_nvram_rwrequest_callback(void *opaque)
+{
+ TPMNvramRWRequest *rwr, *next;
+
+ qemu_mutex_lock(&tpm_nvram_rwrequests_mutex);
+
+ QSIMPLEQ_FOREACH_SAFE(rwr, &tpm_nvram_rwrequests, list, next) {
+ QSIMPLEQ_REMOVE(&tpm_nvram_rwrequests, rwr, TPMNvramRWRequest, list);
+
+ qemu_mutex_unlock(&tpm_nvram_rwrequests_mutex);
+ tpm_nvram_rwrequest_exec(rwr);
+ qemu_mutex_lock(&tpm_nvram_rwrequests_mutex);
+ }
+
+ qemu_mutex_unlock(&tpm_nvram_rwrequests_mutex);
+}
+
+/*
+ * Schedule a bottom-half to read or write a blob to the TPM NVRAM drive
+ */
+static void tpm_nvram_rwrequest_schedule(TPMNvramRWRequest *rwr)
+{
+ qemu_mutex_lock(&tpm_nvram_rwrequests_mutex);
+ QSIMPLEQ_INSERT_TAIL(&tpm_nvram_rwrequests, rwr, list);
+ qemu_mutex_unlock(&tpm_nvram_rwrequests_mutex);
+
+ qemu_bh_schedule(tpm_nvram_bh);
+
+ /* Wait for completion of the read/write request */
+ qemu_mutex_lock(&rwr->completion_mutex);
+ qemu_cond_wait(&rwr->completion, &rwr->completion_mutex);
+ qemu_mutex_unlock(&rwr->completion_mutex);
Race condition: what if the request completes before we reach
qemu_cond_wait()? I suggest initializing rwr->rc to -EINPROGRESS and
doing:
qemu_mutex_lock(&rwr->completion_mutex);
while (rwr->rc == -EINPROGRESS) {
qemu_cond_wait(&rwr->completion, &rwr->completion_mutex);
}
qemu_mutex_unlock(&rwr->completion_mutex);
Good catch. Thanks.
+}
+
+/*
+ * Initialize a TPM NVRAM drive
+ */
+int tpm_nvram_init(BlockDriverState *bdrv)
+{
+ qemu_mutex_init(&tpm_nvram_rwrequests_mutex);
+ tpm_nvram_bh = qemu_bh_new(tpm_nvram_rwrequest_callback, NULL);
+
+ if (bdrv_is_read_only(bdrv)) {
+ DPRINTF("%s: TPM NVRAM drive '%s' is read-only\n", __func__,
+ bdrv->filename);
+ return -EPERM;
+ }
+
+ bdrv_lock_medium(bdrv, true);
+
+ DPRINTF("%s: TPM NVRAM drive '%s' initialized successfully\n", __func__,
+ bdrv->filename);
+
+ return 0;
+}
+
+/*
+ * Read a TPM NVRAM blob from the drive. On success, returns the
+ * number of sectors used by this blob.
+ */
+int tpm_nvram_read(BlockDriverState *bdrv, int64_t sector_num,
+ uint8_t **blob, uint32_t size)
+{
+ int rc;
+ TPMNvramRWRequest *rwr;
+
+ *blob = NULL;
+
+ if (!bdrv) {
+ return -EPERM;
+ }
+
+ if (sector_num < 0) {
+ return -EINVAL;
+ }
Can you let block.c handle these checks to avoid duplication?
Most likely I can remove these.
+
+ rwr = tpm_nvram_rwrequest_init_read(bdrv, sector_num, blob, size);
+ tpm_nvram_rwrequest_schedule(rwr);
+ rc = rwr->rc;
+
+#ifdef TPM_NVRAM_DEBUG
+ if (rc < 0) {
+ DPRINTF("%s: TPM NVRAM read failed\n", __func__);
+ } else {
+ DPRINTF("%s: TPM NVRAM read successful: sector_num=%"PRIu64", "
+ "size=%"PRIu32", num_sectors=%d\n", __func__,
+ rwr->sector_num, rwr->size, rwr->num_sectors);
+ }
+#endif
#ifdef is unnecessary here. The compiler can drop deadcode.
Ok
+
+ tpm_nvram_rwrequest_free(rwr);
+ return rc;
+}
+
+/*
+ * Write a TPM NVRAM blob to the drive. On success, returns the
+ * number of sectors used by this blob.
+ */
+int tpm_nvram_write(BlockDriverState *bdrv, int64_t sector_num,
+ uint8_t *blob, uint32_t size)
+{
+ int rc;
+ TPMNvramRWRequest *rwr;
+
+ if (!bdrv) {
+ return -EPERM;
+ }
+
+ if (sector_num < 0 || !blob) {
+ return -EINVAL;
+ }
+
+ rwr = tpm_nvram_rwrequest_init_write(bdrv, sector_num, blob, size);
+ tpm_nvram_rwrequest_schedule(rwr);
+ rc = rwr->rc;
+
+#ifdef TPM_NVRAM_DEBUG
+ if (rc < 0) {
+ DPRINTF("%s: TPM NVRAM write failed\n", __func__);
+ } else {
+ DPRINTF("%s: TPM NVRAM write successful: sector_num=%"PRIu64", "
+ "size=%"PRIu32", num_sectors=%d\n", __func__,
+ rwr->sector_num, rwr->size, rwr->num_sectors);
+ }
+#endif
+
+ tpm_nvram_rwrequest_free(rwr);
+ return rc;
+}
diff --git a/hw/tpm/tpm_nvram.h b/hw/tpm/tpm_nvram.h
new file mode 100644
index 0000000..fceb4d0
--- /dev/null
+++ b/hw/tpm/tpm_nvram.h
@@ -0,0 +1,25 @@
+/*
+ * TPM NVRAM - enables storage of persistent NVRAM data on an image file
+ *
+ * Copyright (C) 2013 IBM Corporation
+ *
+ * Authors:
+ * Stefan Berger <address@hidden>
+ * Corey Bryant <address@hidden>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#ifndef TPM_TPM_NVRAM_H
+#define TPM_TPM_NVRAM_H
+
+#include "block/block.h"
+
+int tpm_nvram_init(BlockDriverState *bdrv);
+int tpm_nvram_read(BlockDriverState *bdrv, int64_t sector_num,
+ uint8_t **blob, uint32_t size);
+int tpm_nvram_write(BlockDriverState *bdrv, int64_t sector_num,
+ uint8_t *blob, uint32_t size);
+
+#endif
--
1.7.1
--
Regards,
Corey Bryant
[Qemu-devel] [PATCH 2/2] nvram: Add tpm-tis drive support, Corey Bryant, 2013/06/04
Re: [Qemu-devel] [PATCH 0/2] TPM NVRAM persistent storage, Eric Blake, 2013/06/04