mmc: core: Add mmc CMD+ACMD passthrough ioctl

Allows appropriately-privileged applications to send CMD (normal) and ACMD
(application-specific; preceded with CMD55) commands to cards/devices on
the mmc bus.  This is primarily useful for enabling the security
functionality built in to every SD card.

It can also be used as a generic passthrough (e.g. to enable virtual
machines to control mmc bus devices directly).  However, this use case has
not been tested rigorously.  Generic passthrough testing was only conducted
for a few non-security opcodes to prove the feasibility of the passthrough.

Since any opcode can be sent using this passthrough, it is very possible to
render the card/device unusable.  Applications that use this ioctl must
have CAP_SYS_RAWIO.

Security commands tested on TI PCIxx12 (SDHCI), Sigma Designs SMP8652 SoC,
TI OMAP3621/OMAP3630 SoC, Samsung S5PC110 SoC, Qualcomm MSM7200A SoC.

Signed-off-by: John Calixto <john.calixto@modsystems.com>
Reviewed-by: Andrei Warkentin <andreiw@motorola.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Chris Ball <cjb@laptop.org>

1 files changed, 54 insertions, 0 deletions

diff --git a/include/linux/mmc/ioctl.h b/include/linux/mmc/ioctl.h
new file mode 100644
index 00000000000..5baf2983a12
--- /dev/null
+++ b/include/linux/mmc/ioctl.h
@@ -0,0 +1,54 @@
+#ifndef LINUX_MMC_IOCTL_H
+#define LINUX_MMC_IOCTL_H
+struct mmc_ioc_cmd {
+        /* Implies direction of data.  true = write, false = read */
+        int write_flag;
+
+        /* Application-specific command.  true = precede with CMD55 */
+        int is_acmd;
+
+        __u32 opcode;
+        __u32 arg;
+        __u32 response[4];  /* CMD response */
+        unsigned int flags;
+        unsigned int blksz;
+        unsigned int blocks;
+
+        /*
+         * Sleep at least postsleep_min_us useconds, and at most
+         * postsleep_max_us useconds *after* issuing command.  Needed for
+         * some read commands for which cards have no other way of indicating
+         * they're ready for the next command (i.e. there is no equivalent of
+         * a "busy" indicator for read operations).
+         */
+        unsigned int postsleep_min_us;
+        unsigned int postsleep_max_us;
+
+        /*
+         * Override driver-computed timeouts.  Note the difference in units!
+         */
+        unsigned int data_timeout_ns;
+        unsigned int cmd_timeout_ms;
+
+        /*
+         * For 64-bit machines, the next member, ``__u64 data_ptr``, wants to
+         * be 8-byte aligned.  Make sure this struct is the same size when
+         * built for 32-bit.
+         */
+        __u32 __pad;
+
+        /* DAT buffer */
+        __u64 data_ptr;
+};
+#define mmc_ioc_cmd_set_data(ic, ptr) ic.data_ptr = (__u64)(unsigned long) ptr
+
+#define MMC_IOC_CMD _IOWR(MMC_BLOCK_MAJOR, 0, struct mmc_ioc_cmd)
+
+/*
+ * Since this ioctl is only meant to enhance (and not replace) normal access
+ * to the mmc bus device, an upper data transfer limit of MMC_IOC_MAX_BYTES
+ * is enforced per ioctl call.  For larger data transfers, use the normal
+ * block device operations.
+ */
+#define MMC_IOC_MAX_BYTES  (512L * 256)
+#endif  /* LINUX_MMC_IOCTL_H */