include/uapi/linux/user_events.h

/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
/*
 * Copyright (c) 2021, Microsoft Corporation.
 *
 * Authors:
 *   Beau Belgrave <beaub@linux.microsoft.com>
 */
#ifndef _UAPI_LINUX_USER_EVENTS_H
#define _UAPI_LINUX_USER_EVENTS_H

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

#ifdef __KERNEL__
#include <linux/uio.h>
#else
#include <sys/uio.h>
#endif

#define USER_EVENTS_SYSTEM "user_events"
#define USER_EVENTS_PREFIX "u:"

/* Bits 0-6 are for known probe types, Bit 7 is for unknown probes */
#define EVENT_BIT_FTRACE 0
#define EVENT_BIT_PERF 1
#define EVENT_BIT_OTHER 7

#define EVENT_STATUS_FTRACE (1 << EVENT_BIT_FTRACE)
#define EVENT_STATUS_PERF (1 << EVENT_BIT_PERF)
#define EVENT_STATUS_OTHER (1 << EVENT_BIT_OTHER)

/* Create dynamic location entry within a 32-bit value */
#define DYN_LOC(offset, size) ((size) << 16 | (offset))

/* Use raw iterator for attached BPF program(s), no affect on ftrace/perf */
#define FLAG_BPF_ITER (1 << 0)

/*
 * Describes an event registration and stores the results of the registration.
 * This structure is passed to the DIAG_IOCSREG ioctl, callers at a minimum
 * must set the size and name_args before invocation.
 */
struct user_reg {

	/* Input: Size of the user_reg structure being used */
	__u32 size;

	/* Input: Pointer to string with event name, description and flags */
	__u64 name_args;

	/* Output: Byte index of the event within the status page */
	__u32 status_index;

	/* Output: Index of the event to use when writing data */
	__u32 write_index;
};

#define DIAG_IOC_MAGIC '*'

/* Requests to register a user_event */
#define DIAG_IOCSREG _IOWR(DIAG_IOC_MAGIC, 0, struct user_reg*)

/* Requests to delete a user_event */
#define DIAG_IOCSDEL _IOW(DIAG_IOC_MAGIC, 1, char*)

/* Data type that was passed to the BPF program */
enum {
	/* Data resides in kernel space */
	USER_BPF_DATA_KERNEL,

	/* Data resides in user space */
	USER_BPF_DATA_USER,

	/* Data is a pointer to a user_bpf_iter structure */
	USER_BPF_DATA_ITER,
};

/*
 * Describes an iovec iterator that BPF programs can use to access data for
 * a given user_event write() / writev() call.
 */
struct user_bpf_iter {

	/* Offset of the data within the first iovec */
	__u32 iov_offset;

	/* Number of iovec structures */
	__u32 nr_segs;

	/* Pointer to iovec structures */
	const struct iovec *iov;
};

/* Context that BPF programs receive when attached to a user_event */
struct user_bpf_context {

	/* Data type being passed (see union below) */
	__u32 data_type;

	/* Length of the data */
	__u32 data_len;

	/* Pointer to data, varies by data type */
	union {
		/* Kernel data (data_type == USER_BPF_DATA_KERNEL) */
		void *kdata;

		/* User data (data_type == USER_BPF_DATA_USER) */
		void *udata;

		/* Direct iovec (data_type == USER_BPF_DATA_ITER) */
		struct user_bpf_iter *iter;
	};
};

#endif /* _UAPI_LINUX_USER_EVENTS_H */