cregit-Linux how code gets into the kernel

Release 4.12 include/uapi/linux/target_core_user.h

#ifndef __TARGET_CORE_USER_H

#define __TARGET_CORE_USER_H

/* This header will be used by application too */

#include <linux/types.h>
#include <linux/uio.h>


#define TCMU_VERSION "2.0"

/*
 * Ring Design
 * -----------
 *
 * The mmaped area is divided into three parts:
 * 1) The mailbox (struct tcmu_mailbox, below)
 * 2) The command ring
 * 3) Everything beyond the command ring (data)
 *
 * The mailbox tells userspace the offset of the command ring from the
 * start of the shared memory region, and how big the command ring is.
 *
 * The kernel passes SCSI commands to userspace by putting a struct
 * tcmu_cmd_entry in the ring, updating mailbox->cmd_head, and poking
 * userspace via uio's interrupt mechanism.
 *
 * tcmu_cmd_entry contains a header. If the header type is PAD,
 * userspace should skip hdr->length bytes (mod cmdr_size) to find the
 * next cmd_entry.
 *
 * Otherwise, the entry will contain offsets into the mmaped area that
 * contain the cdb and data buffers -- the latter accessible via the
 * iov array. iov addresses are also offsets into the shared area.
 *
 * When userspace is completed handling the command, set
 * entry->rsp.scsi_status, fill in rsp.sense_buffer if appropriate,
 * and also set mailbox->cmd_tail equal to the old cmd_tail plus
 * hdr->length, mod cmdr_size. If cmd_tail doesn't equal cmd_head, it
 * should process the next packet the same way, and so on.
 */


#define TCMU_MAILBOX_VERSION 2

#define ALIGN_SIZE 64 
/* Should be enough for most CPUs */

#define TCMU_MAILBOX_FLAG_CAP_OOOC (1 << 0) 
/* Out-of-order completions */


struct tcmu_mailbox {
	
__u16 version;
	
__u16 flags;
	
__u32 cmdr_off;
	
__u32 cmdr_size;

	
__u32 cmd_head;

	/* Updated by user. On its own cacheline */
	
__u32 cmd_tail __attribute__((__aligned__(ALIGN_SIZE)));


} __packed;


enum tcmu_opcode {
	
TCMU_OP_PAD = 0,
	
TCMU_OP_CMD,
};

/*
 * Only a few opcodes, and length is 8-byte aligned, so use low bits for opcode.
 */

struct tcmu_cmd_entry_hdr {
	
__u32 len_op;
	
__u16 cmd_id;
	
__u8 kflags;

#define TCMU_UFLAG_UNKNOWN_OP 0x1
	
__u8 uflags;


} __packed;


#define TCMU_OP_MASK 0x7


static inline enum tcmu_opcode tcmu_hdr_get_op(__u32 len_op) { return len_op & TCMU_OP_MASK; }

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static inline void tcmu_hdr_set_op(__u32 *len_op, enum tcmu_opcode op) { *len_op &= ~TCMU_OP_MASK; *len_op |= (op & TCMU_OP_MASK); }

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static inline __u32 tcmu_hdr_get_len(__u32 len_op) { return len_op & ~TCMU_OP_MASK; }

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static inline void tcmu_hdr_set_len(__u32 *len_op, __u32 len) { *len_op &= TCMU_OP_MASK; *len_op |= len; }

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/* Currently the same as SCSI_SENSE_BUFFERSIZE */ #define TCMU_SENSE_BUFFERSIZE 96 struct tcmu_cmd_entry { struct tcmu_cmd_entry_hdr hdr; union { struct { __u32 iov_cnt; __u32 iov_bidi_cnt; __u32 iov_dif_cnt; __u64 cdb_off; __u64 __pad1; __u64 __pad2; struct iovec iov[0]; } req; struct { __u8 scsi_status; __u8 __pad1; __u16 __pad2; __u32 __pad3; char sense_buffer[TCMU_SENSE_BUFFERSIZE]; } rsp; }; } __packed; #define TCMU_OP_ALIGN_SIZE sizeof(__u64) enum tcmu_genl_cmd { TCMU_CMD_UNSPEC, TCMU_CMD_ADDED_DEVICE, TCMU_CMD_REMOVED_DEVICE, __TCMU_CMD_MAX, }; #define TCMU_CMD_MAX (__TCMU_CMD_MAX - 1) enum tcmu_genl_attr { TCMU_ATTR_UNSPEC, TCMU_ATTR_DEVICE, TCMU_ATTR_MINOR, __TCMU_ATTR_MAX, }; #define TCMU_ATTR_MAX (__TCMU_ATTR_MAX - 1) #endif

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