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97548575be
The RPMB partition on the eMMC devices is a special area used for storing cryptographically safe information signed by a special secret key. To write and read records from this special area, authentication is needed. The RPMB area is *only* and *exclusively* accessed using ioctl():s from userspace. It is not really a block device, as blocks cannot be read or written from the device, also the signed chunks that can be stored on the RPMB are actually 256 bytes, not 512 making a block device a real bad fit. Currently the RPMB partition spawns a separate block device named /dev/mmcblkNrpmb for each device with an RPMB partition, including the creation of a block queue with its own kernel thread and all overhead associated with this. On the Ux500 HREFv60 platform, for example, the two eMMCs means that two block queues with separate threads are created for no use whatsoever. I have concluded that this block device design for RPMB is actually pretty wrong. The RPMB area should have been designed to be accessed from /dev/mmcblkN directly, using ioctl()s on the main block device. It is however way too late to change that, since userspace expects to open an RPMB device in /dev/mmcblkNrpmb and we cannot break userspace. This patch tries to amend the situation using the following strategy: - Stop creating a block device for the RPMB partition/area - Instead create a custom, dynamic character device with the same name. - Make this new character device support exactly the same set of ioctl()s as the old block device. - Wrap the requests back to the same ioctl() handlers, but issue them on the block queue of the main partition/area, i.e. /dev/mmcblkN We need to create a special "rpmb" bus type in order to get udev and/or busybox hot/coldplug to instantiate the device node properly. Before the patch, this appears in 'ps aux': 101 root 0:00 [mmcqd/2rpmb] 123 root 0:00 [mmcqd/3rpmb] After applying the patch these surplus block queue threads are gone, but RPMB is as usable as ever using the userspace MMC tools, such as 'mmc rpmb read-counter'. We get instead those dynamice devices in /dev: brw-rw---- 1 root root 179, 0 Jan 1 2000 mmcblk0 brw-rw---- 1 root root 179, 1 Jan 1 2000 mmcblk0p1 brw-rw---- 1 root root 179, 2 Jan 1 2000 mmcblk0p2 brw-rw---- 1 root root 179, 5 Jan 1 2000 mmcblk0p5 brw-rw---- 1 root root 179, 8 Jan 1 2000 mmcblk2 brw-rw---- 1 root root 179, 16 Jan 1 2000 mmcblk2boot0 brw-rw---- 1 root root 179, 24 Jan 1 2000 mmcblk2boot1 crw-rw---- 1 root root 248, 0 Jan 1 2000 mmcblk2rpmb brw-rw---- 1 root root 179, 32 Jan 1 2000 mmcblk3 brw-rw---- 1 root root 179, 40 Jan 1 2000 mmcblk3boot0 brw-rw---- 1 root root 179, 48 Jan 1 2000 mmcblk3boot1 brw-rw---- 1 root root 179, 33 Jan 1 2000 mmcblk3p1 crw-rw---- 1 root root 248, 1 Jan 1 2000 mmcblk3rpmb Notice the (248,0) and (248,1) character devices for RPMB. Cc: Tomas Winkler <tomas.winkler@intel.com> Signed-off-by: Linus Walleij <linus.walleij@linaro.org> Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
88 lines
2.2 KiB
C
88 lines
2.2 KiB
C
#ifndef MMC_QUEUE_H
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#define MMC_QUEUE_H
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#include <linux/types.h>
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#include <linux/blkdev.h>
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#include <linux/blk-mq.h>
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#include <linux/mmc/core.h>
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#include <linux/mmc/host.h>
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static inline struct mmc_queue_req *req_to_mmc_queue_req(struct request *rq)
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{
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return blk_mq_rq_to_pdu(rq);
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}
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struct mmc_queue_req;
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static inline struct request *mmc_queue_req_to_req(struct mmc_queue_req *mqr)
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{
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return blk_mq_rq_from_pdu(mqr);
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}
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struct task_struct;
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struct mmc_blk_data;
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struct mmc_blk_ioc_data;
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struct mmc_blk_request {
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struct mmc_request mrq;
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struct mmc_command sbc;
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struct mmc_command cmd;
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struct mmc_command stop;
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struct mmc_data data;
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int retune_retry_done;
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};
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/**
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* enum mmc_drv_op - enumerates the operations in the mmc_queue_req
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* @MMC_DRV_OP_IOCTL: ioctl operation
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* @MMC_DRV_OP_IOCTL_RPMB: RPMB-oriented ioctl operation
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* @MMC_DRV_OP_BOOT_WP: write protect boot partitions
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* @MMC_DRV_OP_GET_CARD_STATUS: get card status
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* @MMC_DRV_OP_GET_EXT_CSD: get the EXT CSD from an eMMC card
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*/
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enum mmc_drv_op {
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MMC_DRV_OP_IOCTL,
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MMC_DRV_OP_IOCTL_RPMB,
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MMC_DRV_OP_BOOT_WP,
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MMC_DRV_OP_GET_CARD_STATUS,
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MMC_DRV_OP_GET_EXT_CSD,
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};
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struct mmc_queue_req {
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struct mmc_blk_request brq;
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struct scatterlist *sg;
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struct mmc_async_req areq;
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enum mmc_drv_op drv_op;
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int drv_op_result;
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void *drv_op_data;
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unsigned int ioc_count;
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};
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struct mmc_queue {
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struct mmc_card *card;
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struct task_struct *thread;
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struct semaphore thread_sem;
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bool suspended;
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bool asleep;
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struct mmc_blk_data *blkdata;
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struct request_queue *queue;
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/*
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* FIXME: this counter is not a very reliable way of keeping
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* track of how many requests that are ongoing. Switch to just
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* letting the block core keep track of requests and per-request
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* associated mmc_queue_req data.
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*/
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int qcnt;
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};
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extern int mmc_init_queue(struct mmc_queue *, struct mmc_card *, spinlock_t *,
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const char *);
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extern void mmc_cleanup_queue(struct mmc_queue *);
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extern void mmc_queue_suspend(struct mmc_queue *);
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extern void mmc_queue_resume(struct mmc_queue *);
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extern unsigned int mmc_queue_map_sg(struct mmc_queue *,
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struct mmc_queue_req *);
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extern int mmc_access_rpmb(struct mmc_queue *);
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#endif
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