[PATCH v7 04/11] drm: revocation check at drm subsystem
Harry Wentland
hwentlan at amd.com
Thu Sep 12 00:15:32 UTC 2019
Adding a couple AMD guys.
I know this is already merged but I have a few questions after some
internal discussions.
On 2019-05-07 12:27 p.m., Ramalingam C wrote:
> On every hdcp revocation check request SRM is read from fw file
> /lib/firmware/display_hdcp_srm.bin
>
According to section 5 of the HDCP 2.3 spec [1] a device compliant with
HDCP 2.0 and higher must be capable of storing and updating the SRM in
non-volatile memory. Section 5.2 describes how this SRM needs to be
updated when a new version is served alongside protected content.
Isn't /lib/firmware intended for static firmware making updates to the
folder problematic for anyone but the system's package maintainer? I've
heard /lib might even be treated as read-only in certain environments.
This would mean it'd be impossible to support HDCP 2.x on those systems.
Wouldn't it be easier to provide a sysfs entry for SRM that allows
userspace (e.g. system startup/shutdown scripts) to (a) retrieve the SRM
from the HDCP implementation for non-volatile storage and (b) to pass
the SRM to the HDCP implementation for revocation checking?
[1]
https://www.digital-cp.com/sites/default/files/HDCP%20on%20HDMI%20Specification%20Rev2_3.pdf
Thanks,
Harry
> SRM table is parsed and stored at drm_hdcp.c, with functions exported
> for the services for revocation check from drivers (which
> implements the HDCP authentication)
>
> This patch handles the HDCP1.4 and 2.2 versions of SRM table.
>
> v2:
> moved the uAPI to request_firmware_direct() [Daniel]
> v3:
> kdoc added. [Daniel]
> srm_header unified and bit field definitions are removed. [Daniel]
> locking improved. [Daniel]
> vrl length violation is fixed. [Daniel]
> v4:
> s/__swab16/be16_to_cpu [Daniel]
> be24_to_cpu is done through a global func [Daniel]
> Unused variables are removed. [Daniel]
> unchecked return values are dropped from static funcs [Daniel]
>
> Signed-off-by: Ramalingam C <ramalingam.c at intel.com>
> Acked-by: Satyeshwar Singh <satyeshwar.singh at intel.com>
> Reviewed-by: Daniel Vetter <daniel at ffwll.ch>
> ---
> Documentation/gpu/drm-kms-helpers.rst | 6 +
> drivers/gpu/drm/Makefile | 2 +-
> drivers/gpu/drm/drm_hdcp.c | 333 ++++++++++++++++++++++++++
> drivers/gpu/drm/drm_internal.h | 4 +
> drivers/gpu/drm/drm_sysfs.c | 2 +
> include/drm/drm_hdcp.h | 24 ++
> 6 files changed, 370 insertions(+), 1 deletion(-)
> create mode 100644 drivers/gpu/drm/drm_hdcp.c
>
> diff --git a/Documentation/gpu/drm-kms-helpers.rst b/Documentation/gpu/drm-kms-helpers.rst
> index 14102ae035dc..0fe726a6ee67 100644
> --- a/Documentation/gpu/drm-kms-helpers.rst
> +++ b/Documentation/gpu/drm-kms-helpers.rst
> @@ -181,6 +181,12 @@ Panel Helper Reference
> .. kernel-doc:: drivers/gpu/drm/drm_panel_orientation_quirks.c
> :export:
>
> +HDCP Helper Functions Reference
> +===============================
> +
> +.. kernel-doc:: drivers/gpu/drm/drm_hdcp.c
> + :export:
> +
> Display Port Helper Functions Reference
> =======================================
>
> diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
> index 72f5036d9bfa..dd02e9dec810 100644
> --- a/drivers/gpu/drm/Makefile
> +++ b/drivers/gpu/drm/Makefile
> @@ -17,7 +17,7 @@ drm-y := drm_auth.o drm_cache.o \
> drm_plane.o drm_color_mgmt.o drm_print.o \
> drm_dumb_buffers.o drm_mode_config.o drm_vblank.o \
> drm_syncobj.o drm_lease.o drm_writeback.o drm_client.o \
> - drm_atomic_uapi.o
> + drm_atomic_uapi.o drm_hdcp.o
>
> drm-$(CONFIG_DRM_LEGACY) += drm_legacy_misc.o drm_bufs.o drm_context.o drm_dma.o drm_scatter.o drm_lock.o
> drm-$(CONFIG_DRM_LIB_RANDOM) += lib/drm_random.o
> diff --git a/drivers/gpu/drm/drm_hdcp.c b/drivers/gpu/drm/drm_hdcp.c
> new file mode 100644
> index 000000000000..5e5409505c31
> --- /dev/null
> +++ b/drivers/gpu/drm/drm_hdcp.c
> @@ -0,0 +1,333 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2019 Intel Corporation.
> + *
> + * Authors:
> + * Ramalingam C <ramalingam.c at intel.com>
> + */
> +
> +#include <linux/device.h>
> +#include <linux/err.h>
> +#include <linux/gfp.h>
> +#include <linux/export.h>
> +#include <linux/slab.h>
> +#include <linux/firmware.h>
> +
> +#include <drm/drm_hdcp.h>
> +#include <drm/drm_sysfs.h>
> +#include <drm/drm_print.h>
> +#include <drm/drm_device.h>
> +
> +struct hdcp_srm {
> + u32 revoked_ksv_cnt;
> + u8 *revoked_ksv_list;
> +
> + /* Mutex to protect above struct member */
> + struct mutex mutex;
> +} *srm_data;
> +
> +static inline void drm_hdcp_print_ksv(const u8 *ksv)
> +{
> + DRM_DEBUG("\t%#02x, %#02x, %#02x, %#02x, %#02x\n",
> + ksv[0], ksv[1], ksv[2], ksv[3], ksv[4]);
> +}
> +
> +static u32 drm_hdcp_get_revoked_ksv_count(const u8 *buf, u32 vrls_length)
> +{
> + u32 parsed_bytes = 0, ksv_count = 0, vrl_ksv_cnt, vrl_sz;
> +
> + while (parsed_bytes < vrls_length) {
> + vrl_ksv_cnt = *buf;
> + ksv_count += vrl_ksv_cnt;
> +
> + vrl_sz = (vrl_ksv_cnt * DRM_HDCP_KSV_LEN) + 1;
> + buf += vrl_sz;
> + parsed_bytes += vrl_sz;
> + }
> +
> + /*
> + * When vrls are not valid, ksvs are not considered.
> + * Hence SRM will be discarded.
> + */
> + if (parsed_bytes != vrls_length)
> + ksv_count = 0;
> +
> + return ksv_count;
> +}
> +
> +static u32 drm_hdcp_get_revoked_ksvs(const u8 *buf, u8 *revoked_ksv_list,
> + u32 vrls_length)
> +{
> + u32 parsed_bytes = 0, ksv_count = 0;
> + u32 vrl_ksv_cnt, vrl_ksv_sz, vrl_idx = 0;
> +
> + do {
> + vrl_ksv_cnt = *buf;
> + vrl_ksv_sz = vrl_ksv_cnt * DRM_HDCP_KSV_LEN;
> +
> + buf++;
> +
> + DRM_DEBUG("vrl: %d, Revoked KSVs: %d\n", vrl_idx++,
> + vrl_ksv_cnt);
> + memcpy(revoked_ksv_list, buf, vrl_ksv_sz);
> +
> + ksv_count += vrl_ksv_cnt;
> + revoked_ksv_list += vrl_ksv_sz;
> + buf += vrl_ksv_sz;
> +
> + parsed_bytes += (vrl_ksv_sz + 1);
> + } while (parsed_bytes < vrls_length);
> +
> + return ksv_count;
> +}
> +
> +static inline u32 get_vrl_length(const u8 *buf)
> +{
> + return drm_hdcp_be24_to_cpu(buf);
> +}
> +
> +static int drm_hdcp_parse_hdcp1_srm(const u8 *buf, size_t count)
> +{
> + struct hdcp_srm_header *header;
> + u32 vrl_length, ksv_count;
> +
> + if (count < (sizeof(struct hdcp_srm_header) +
> + DRM_HDCP_1_4_VRL_LENGTH_SIZE + DRM_HDCP_1_4_DCP_SIG_SIZE)) {
> + DRM_ERROR("Invalid blob length\n");
> + return -EINVAL;
> + }
> +
> + header = (struct hdcp_srm_header *)buf;
> + DRM_DEBUG("SRM ID: 0x%x, SRM Ver: 0x%x, SRM Gen No: 0x%x\n",
> + header->srm_id,
> + be16_to_cpu(header->srm_version), header->srm_gen_no);
> +
> + WARN_ON(header->reserved);
> +
> + buf = buf + sizeof(*header);
> + vrl_length = get_vrl_length(buf);
> + if (count < (sizeof(struct hdcp_srm_header) + vrl_length) ||
> + vrl_length < (DRM_HDCP_1_4_VRL_LENGTH_SIZE +
> + DRM_HDCP_1_4_DCP_SIG_SIZE)) {
> + DRM_ERROR("Invalid blob length or vrl length\n");
> + return -EINVAL;
> + }
> +
> + /* Length of the all vrls combined */
> + vrl_length -= (DRM_HDCP_1_4_VRL_LENGTH_SIZE +
> + DRM_HDCP_1_4_DCP_SIG_SIZE);
> +
> + if (!vrl_length) {
> + DRM_ERROR("No vrl found\n");
> + return -EINVAL;
> + }
> +
> + buf += DRM_HDCP_1_4_VRL_LENGTH_SIZE;
> + ksv_count = drm_hdcp_get_revoked_ksv_count(buf, vrl_length);
> + if (!ksv_count) {
> + DRM_DEBUG("Revoked KSV count is 0\n");
> + return count;
> + }
> +
> + kfree(srm_data->revoked_ksv_list);
> + srm_data->revoked_ksv_list = kcalloc(ksv_count, DRM_HDCP_KSV_LEN,
> + GFP_KERNEL);
> + if (!srm_data->revoked_ksv_list) {
> + DRM_ERROR("Out of Memory\n");
> + return -ENOMEM;
> + }
> +
> + if (drm_hdcp_get_revoked_ksvs(buf, srm_data->revoked_ksv_list,
> + vrl_length) != ksv_count) {
> + srm_data->revoked_ksv_cnt = 0;
> + kfree(srm_data->revoked_ksv_list);
> + return -EINVAL;
> + }
> +
> + srm_data->revoked_ksv_cnt = ksv_count;
> + return count;
> +}
> +
> +static int drm_hdcp_parse_hdcp2_srm(const u8 *buf, size_t count)
> +{
> + struct hdcp_srm_header *header;
> + u32 vrl_length, ksv_count, ksv_sz;
> +
> + if (count < (sizeof(struct hdcp_srm_header) +
> + DRM_HDCP_2_VRL_LENGTH_SIZE + DRM_HDCP_2_DCP_SIG_SIZE)) {
> + DRM_ERROR("Invalid blob length\n");
> + return -EINVAL;
> + }
> +
> + header = (struct hdcp_srm_header *)buf;
> + DRM_DEBUG("SRM ID: 0x%x, SRM Ver: 0x%x, SRM Gen No: 0x%x\n",
> + header->srm_id & DRM_HDCP_SRM_ID_MASK,
> + be16_to_cpu(header->srm_version), header->srm_gen_no);
> +
> + if (header->reserved)
> + return -EINVAL;
> +
> + buf = buf + sizeof(*header);
> + vrl_length = get_vrl_length(buf);
> +
> + if (count < (sizeof(struct hdcp_srm_header) + vrl_length) ||
> + vrl_length < (DRM_HDCP_2_VRL_LENGTH_SIZE +
> + DRM_HDCP_2_DCP_SIG_SIZE)) {
> + DRM_ERROR("Invalid blob length or vrl length\n");
> + return -EINVAL;
> + }
> +
> + /* Length of the all vrls combined */
> + vrl_length -= (DRM_HDCP_2_VRL_LENGTH_SIZE +
> + DRM_HDCP_2_DCP_SIG_SIZE);
> +
> + if (!vrl_length) {
> + DRM_ERROR("No vrl found\n");
> + return -EINVAL;
> + }
> +
> + buf += DRM_HDCP_2_VRL_LENGTH_SIZE;
> + ksv_count = (*buf << 2) | DRM_HDCP_2_KSV_COUNT_2_LSBITS(*(buf + 1));
> + if (!ksv_count) {
> + DRM_DEBUG("Revoked KSV count is 0\n");
> + return count;
> + }
> +
> + kfree(srm_data->revoked_ksv_list);
> + srm_data->revoked_ksv_list = kcalloc(ksv_count, DRM_HDCP_KSV_LEN,
> + GFP_KERNEL);
> + if (!srm_data->revoked_ksv_list) {
> + DRM_ERROR("Out of Memory\n");
> + return -ENOMEM;
> + }
> +
> + ksv_sz = ksv_count * DRM_HDCP_KSV_LEN;
> + buf += DRM_HDCP_2_NO_OF_DEV_PLUS_RESERVED_SZ;
> +
> + DRM_DEBUG("Revoked KSVs: %d\n", ksv_count);
> + memcpy(srm_data->revoked_ksv_list, buf, ksv_sz);
> +
> + srm_data->revoked_ksv_cnt = ksv_count;
> + return count;
> +}
> +
> +static inline bool is_srm_version_hdcp1(const u8 *buf)
> +{
> + return *buf == (u8)(DRM_HDCP_1_4_SRM_ID << 4);
> +}
> +
> +static inline bool is_srm_version_hdcp2(const u8 *buf)
> +{
> + return *buf == (u8)(DRM_HDCP_2_SRM_ID << 4 | DRM_HDCP_2_INDICATOR);
> +}
> +
> +static void drm_hdcp_srm_update(const u8 *buf, size_t count)
> +{
> + if (count < sizeof(struct hdcp_srm_header))
> + return;
> +
> + if (is_srm_version_hdcp1(buf))
> + drm_hdcp_parse_hdcp1_srm(buf, count);
> + else if (is_srm_version_hdcp2(buf))
> + drm_hdcp_parse_hdcp2_srm(buf, count);
> +}
> +
> +void drm_hdcp_request_srm(struct drm_device *drm_dev)
> +{
> + char fw_name[36] = "display_hdcp_srm.bin";
> + const struct firmware *fw;
> +
> + int ret;
> +
> + ret = request_firmware_direct(&fw, (const char *)fw_name,
> + drm_dev->dev);
> + if (ret < 0)
> + goto exit;
> +
> + if (fw->size && fw->data)
> + drm_hdcp_srm_update(fw->data, fw->size);
> +
> +exit:
> + release_firmware(fw);
> +}
> +
> +/**
> + * drm_hdcp_check_ksvs_revoked - Check the revoked status of the IDs
> + *
> + * @drm_dev: drm_device for which HDCP revocation check is requested
> + * @ksvs: List of KSVs (HDCP receiver IDs)
> + * @ksv_count: KSV count passed in through @ksvs
> + *
> + * This function reads the HDCP System renewability Message(SRM Table)
> + * from userspace as a firmware and parses it for the revoked HDCP
> + * KSVs(Receiver IDs) detected by DCP LLC. Once the revoked KSVs are known,
> + * revoked state of the KSVs in the list passed in by display drivers are
> + * decided and response is sent.
> + *
> + * SRM should be presented in the name of "display_hdcp_srm.bin".
> + *
> + * Returns:
> + * TRUE on any of the KSV is revoked, else FALSE.
> + */
> +bool drm_hdcp_check_ksvs_revoked(struct drm_device *drm_dev, u8 *ksvs,
> + u32 ksv_count)
> +{
> + u32 rev_ksv_cnt, cnt, i, j;
> + u8 *rev_ksv_list;
> +
> + if (!srm_data)
> + return false;
> +
> + mutex_lock(&srm_data->mutex);
> + drm_hdcp_request_srm(drm_dev);
> +
> + rev_ksv_cnt = srm_data->revoked_ksv_cnt;
> + rev_ksv_list = srm_data->revoked_ksv_list;
> +
> + /* If the Revoked ksv list is empty */
> + if (!rev_ksv_cnt || !rev_ksv_list) {
> + mutex_unlock(&srm_data->mutex);
> + return false;
> + }
> +
> + for (cnt = 0; cnt < ksv_count; cnt++) {
> + rev_ksv_list = srm_data->revoked_ksv_list;
> + for (i = 0; i < rev_ksv_cnt; i++) {
> + for (j = 0; j < DRM_HDCP_KSV_LEN; j++)
> + if (ksvs[j] != rev_ksv_list[j]) {
> + break;
> + } else if (j == (DRM_HDCP_KSV_LEN - 1)) {
> + DRM_DEBUG("Revoked KSV is ");
> + drm_hdcp_print_ksv(ksvs);
> + mutex_unlock(&srm_data->mutex);
> + return true;
> + }
> + /* Move the offset to next KSV in the revoked list */
> + rev_ksv_list += DRM_HDCP_KSV_LEN;
> + }
> +
> + /* Iterate to next ksv_offset */
> + ksvs += DRM_HDCP_KSV_LEN;
> + }
> + mutex_unlock(&srm_data->mutex);
> + return false;
> +}
> +EXPORT_SYMBOL_GPL(drm_hdcp_check_ksvs_revoked);
> +
> +int drm_setup_hdcp_srm(struct class *drm_class)
> +{
> + srm_data = kzalloc(sizeof(*srm_data), GFP_KERNEL);
> + if (!srm_data)
> + return -ENOMEM;
> + mutex_init(&srm_data->mutex);
> +
> + return 0;
> +}
> +
> +void drm_teardown_hdcp_srm(struct class *drm_class)
> +{
> + if (srm_data) {
> + kfree(srm_data->revoked_ksv_list);
> + kfree(srm_data);
> + }
> +}
> diff --git a/drivers/gpu/drm/drm_internal.h b/drivers/gpu/drm/drm_internal.h
> index e19ac7ca602d..476a422414f6 100644
> --- a/drivers/gpu/drm/drm_internal.h
> +++ b/drivers/gpu/drm/drm_internal.h
> @@ -201,3 +201,7 @@ int drm_syncobj_query_ioctl(struct drm_device *dev, void *data,
> void drm_framebuffer_print_info(struct drm_printer *p, unsigned int indent,
> const struct drm_framebuffer *fb);
> int drm_framebuffer_debugfs_init(struct drm_minor *minor);
> +
> +/* drm_hdcp.c */
> +int drm_setup_hdcp_srm(struct class *drm_class);
> +void drm_teardown_hdcp_srm(struct class *drm_class);
> diff --git a/drivers/gpu/drm/drm_sysfs.c b/drivers/gpu/drm/drm_sysfs.c
> index ecb7b33002bb..18b1ac442997 100644
> --- a/drivers/gpu/drm/drm_sysfs.c
> +++ b/drivers/gpu/drm/drm_sysfs.c
> @@ -78,6 +78,7 @@ int drm_sysfs_init(void)
> }
>
> drm_class->devnode = drm_devnode;
> + drm_setup_hdcp_srm(drm_class);
> return 0;
> }
>
> @@ -90,6 +91,7 @@ void drm_sysfs_destroy(void)
> {
> if (IS_ERR_OR_NULL(drm_class))
> return;
> + drm_teardown_hdcp_srm(drm_class);
> class_remove_file(drm_class, &class_attr_version.attr);
> class_destroy(drm_class);
> drm_class = NULL;
> diff --git a/include/drm/drm_hdcp.h b/include/drm/drm_hdcp.h
> index 1cc66df05a43..2f0335d0a50f 100644
> --- a/include/drm/drm_hdcp.h
> +++ b/include/drm/drm_hdcp.h
> @@ -265,4 +265,28 @@ void drm_hdcp_cpu_to_be24(u8 seq_num[HDCP_2_2_SEQ_NUM_LEN], u32 val)
> seq_num[2] = val;
> }
>
> +#define DRM_HDCP_SRM_GEN1_MAX_BYTES (5 * 1024)
> +#define DRM_HDCP_1_4_SRM_ID 0x8
> +#define DRM_HDCP_SRM_ID_MASK (0xF << 4)
> +#define DRM_HDCP_1_4_VRL_LENGTH_SIZE 3
> +#define DRM_HDCP_1_4_DCP_SIG_SIZE 40
> +#define DRM_HDCP_2_SRM_ID 0x9
> +#define DRM_HDCP_2_INDICATOR 0x1
> +#define DRM_HDCP_2_INDICATOR_MASK 0xF
> +#define DRM_HDCP_2_VRL_LENGTH_SIZE 3
> +#define DRM_HDCP_2_DCP_SIG_SIZE 384
> +#define DRM_HDCP_2_NO_OF_DEV_PLUS_RESERVED_SZ 4
> +#define DRM_HDCP_2_KSV_COUNT_2_LSBITS(byte) (((byte) & 0xC) >> 6)
> +
> +struct hdcp_srm_header {
> + u8 srm_id;
> + u8 reserved;
> + __be16 srm_version;
> + u8 srm_gen_no;
> +} __packed;
> +
> +struct drm_device;
> +
> +bool drm_hdcp_check_ksvs_revoked(struct drm_device *dev,
> + u8 *ksvs, u32 ksv_count);
> #endif
> --
> 2.19.1
>
> _______________________________________________
> dri-devel mailing list
> dri-devel at lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel
>
More information about the dri-devel
mailing list