Commit 09bb8856 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'trace-v5.18-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace 

Pull more tracing updates from Steven Rostedt:

 - Rename the staging files to give them some meaning. Just
   stage1,stag2,etc, does not show what they are for

 - Check for NULL from allocation in bootconfig

 - Hold event mutex for dyn_event call in user events

 - Mark user events to broken (to work on the API)

 - Remove eBPF updates from user events

 - Remove user events from uapi header to keep it from being installed.

 - Move ftrace_graph_is_dead() into inline as it is called from hot
   paths and also convert it into a static branch.

* tag 'trace-v5.18-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
  tracing: Move user_events.h temporarily out of include/uapi
  ftrace: Make ftrace_graph_is_dead() a static branch
  tracing: Set user_events to BROKEN
  tracing/user_events: Remove eBPF interfaces
  tracing/user_events: Hold event_mutex during dyn_event_add
  proc: bootconfig: Add null pointer check
  tracing: Rename the staging files for trace_events
parents 34a53ff9 5cfff569

Documentation/trace/user_events.rst

+3 −11
Original line number Diff line number Diff line
@@ -7,7 +7,7 @@ user_events: User-based Event Tracing 
Overview

--------

User based trace events allow user processes to create events and trace data

that can be viewed via existing tools, such as ftrace, perf and eBPF.

that can be viewed via existing tools, such as ftrace and perf.

To enable this feature, build your kernel with CONFIG_USER_EVENTS=y.



Programs can view status of the events via
@@ -67,8 +67,7 @@ The command string format is as follows:: 


Supported Flags

^^^^^^^^^^^^^^^

**BPF_ITER** - EBPF programs attached to this event will get the raw iovec

struct instead of any data copies for max performance.

None yet



Field Format

^^^^^^^^^^^^
@@ -160,7 +159,7 @@ The following values are defined to aid in checking what has been attached: 


**EVENT_STATUS_FTRACE** - Bit set if ftrace has been attached (Bit 0).



**EVENT_STATUS_PERF** - Bit set if perf/eBPF has been attached (Bit 1).

**EVENT_STATUS_PERF** - Bit set if perf has been attached (Bit 1).



Writing Data

------------
@@ -204,13 +203,6 @@ It's advised for user programs to do the following:: 


**NOTE:** *The write_index is not emitted out into the trace being recorded.*



EBPF

----

EBPF programs that attach to a user-based event tracepoint are given a pointer

to a struct user_bpf_context. The bpf context contains the data type (which can

be a user or kernel buffer, or can be a pointer to the iovec) and the data

length that was emitted (minus the write_index).



Example Code

------------

See sample code in samples/user_events.

fs/proc/bootconfig.c

+2 −0
Original line number Diff line number Diff line
@@ -32,6 +32,8 @@ static int __init copy_xbc_key_value_list(char *dst, size_t size) 
	int ret = 0;



	key = kzalloc(XBC_KEYLEN_MAX, GFP_KERNEL);

	if (!key)

		return -ENOMEM;



	xbc_for_each_key_value(leaf, val) {

		ret = xbc_node_compose_key(leaf, key, XBC_KEYLEN_MAX);

include/linux/ftrace.h

+15 −1
Original line number Diff line number Diff line
@@ -9,6 +9,7 @@ 


#include <linux/trace_recursion.h>

#include <linux/trace_clock.h>

#include <linux/jump_label.h>

#include <linux/kallsyms.h>

#include <linux/linkage.h>

#include <linux/bitops.h>
@@ -1018,7 +1019,20 @@ unsigned long ftrace_graph_ret_addr(struct task_struct *task, int *idx, 
extern int register_ftrace_graph(struct fgraph_ops *ops);

extern void unregister_ftrace_graph(struct fgraph_ops *ops);



extern bool ftrace_graph_is_dead(void);

/**

 * ftrace_graph_is_dead - returns true if ftrace_graph_stop() was called

 *

 * ftrace_graph_stop() is called when a severe error is detected in

 * the function graph tracing. This function is called by the critical

 * paths of function graph to keep those paths from doing any more harm.

 */

DECLARE_STATIC_KEY_FALSE(kill_ftrace_graph);



static inline bool ftrace_graph_is_dead(void)

{

	return static_branch_unlikely(&kill_ftrace_graph);

}



extern void ftrace_graph_stop(void);



/* The current handlers in use */

include/linux/user_events.h

+0 −53
Original line number Diff line number Diff line
@@ -32,9 +32,6 @@ 
/* 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
@@ -63,54 +60,4 @@ 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 */