[PATCH] tracing/user_events: Remove eBPF interfaces

[PATCH] tracing/user_events: Remove eBPF interfaces

[Beau Belgrave]

Remove eBPF interfaces within user_events to ensure they are fully
reviewed.

Link: https://lore.kernel.org/all/20220329165718.GA10381@kbox/

Signed-off-by: Beau Belgrave <beaub@linux.microsoft.com>
---
 Documentation/trace/user_events.rst | 14 ++----
 include/uapi/linux/user_events.h    | 53 ---------------------
 kernel/trace/trace_events_user.c    | 73 +----------------------------
 3 files changed, 4 insertions(+), 136 deletions(-)

diff --git a/Documentation/trace/user_events.rst b/Documentation/trace/user_events.rst
index bddedabaca80..c180936f49fc 100644
--- a/Documentation/trace/user_events.rst
+++ b/Documentation/trace/user_events.rst
@@ -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.
diff --git a/include/uapi/linux/user_events.h b/include/uapi/linux/user_events.h
index e570840571e1..736e05603463 100644
--- a/include/uapi/linux/user_events.h
+++ b/include/uapi/linux/user_events.h
@@ -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 */
diff --git a/kernel/trace/trace_events_user.c b/kernel/trace/trace_events_user.c
index 8b3d241a31c2..3bc97e44253f 100644
--- a/kernel/trace/trace_events_user.c
+++ b/kernel/trace/trace_events_user.c
@@ -42,9 +42,6 @@
 #define MAX_FIELD_ARRAY_SIZE 1024
 #define MAX_FIELD_ARG_NAME 256
 
-#define MAX_BPF_COPY_SIZE PAGE_SIZE
-#define MAX_STACK_BPF_DATA 512
-
 static char *register_page_data;
 
 static DEFINE_MUTEX(reg_mutex);
@@ -405,19 +402,6 @@ static int user_event_parse_field(char *field, struct user_event *user,
 				    type[0] != 'u', FILTER_OTHER);
 }
 
-static void user_event_parse_flags(struct user_event *user, char *flags)
-{
-	char *flag;
-
-	if (flags == NULL)
-		return;
-
-	while ((flag = strsep(&flags, ",")) != NULL) {
-		if (strcmp(flag, "BPF_ITER") == 0)
-			user->flags |= FLAG_BPF_ITER;
-	}
-}
-
 static int user_event_parse_fields(struct user_event *user, char *args)
 {
 	char *field;
@@ -713,64 +697,14 @@ static void user_event_ftrace(struct user_event *user, struct iov_iter *i,
 }
 
 #ifdef CONFIG_PERF_EVENTS
-static void user_event_bpf(struct user_event *user, struct iov_iter *i)
-{
-	struct user_bpf_context context;
-	struct user_bpf_iter bpf_i;
-	char fast_data[MAX_STACK_BPF_DATA];
-	void *temp = NULL;
-
-	if ((user->flags & FLAG_BPF_ITER) && iter_is_iovec(i)) {
-		/* Raw iterator */
-		context.data_type = USER_BPF_DATA_ITER;
-		context.data_len = i->count;
-		context.iter = &bpf_i;
-
-		bpf_i.iov_offset = i->iov_offset;
-		bpf_i.iov = i->iov;
-		bpf_i.nr_segs = i->nr_segs;
-	} else if (i->nr_segs == 1 && iter_is_iovec(i)) {
-		/* Single buffer from user */
-		context.data_type = USER_BPF_DATA_USER;
-		context.data_len = i->count;
-		context.udata = i->iov->iov_base + i->iov_offset;
-	} else {
-		/* Multi buffer from user */
-		struct iov_iter copy = *i;
-		size_t copy_size = min_t(size_t, i->count, MAX_BPF_COPY_SIZE);
-
-		context.data_type = USER_BPF_DATA_KERNEL;
-		context.kdata = fast_data;
-
-		if (unlikely(copy_size > sizeof(fast_data))) {
-			temp = kmalloc(copy_size, GFP_NOWAIT);
-
-			if (temp)
-				context.kdata = temp;
-			else
-				copy_size = sizeof(fast_data);
-		}
-
-		context.data_len = copy_nofault(context.kdata,
-						copy_size, &copy);
-	}
-
-	trace_call_bpf(&user->call, &context);
-
-	kfree(temp);
-}
-
 /*
- * Writes the user supplied payload out to perf ring buffer or eBPF program.
+ * Writes the user supplied payload out to perf ring buffer.
  */
 static void user_event_perf(struct user_event *user, struct iov_iter *i,
 			    void *tpdata, bool *faulted)
 {
 	struct hlist_head *perf_head;
 
-	if (bpf_prog_array_valid(&user->call))
-		user_event_bpf(user, i);
-
 	perf_head = this_cpu_ptr(user->call.perf_events);
 
 	if (perf_head && !hlist_empty(perf_head)) {
@@ -1136,8 +1070,6 @@ static int user_event_parse(char *name, char *args, char *flags,
 
 	user->tracepoint.name = name;
 
-	user_event_parse_flags(user, flags);
-
 	ret = user_event_parse_fields(user, args);
 
 	if (ret)
@@ -1575,9 +1507,6 @@ static int user_seq_show(struct seq_file *m, void *p)
 			busy++;
 		}
 
-		if (flags & FLAG_BPF_ITER)
-			seq_puts(m, " FLAG:BPF_ITER");
-
 		seq_puts(m, "\n");
 		active++;
 	}

base-commit: 5efabdadcf4a5b9a37847ecc85ba71cf2eff0fcf
-- 
2.25.1

Re: [PATCH] tracing/user_events: Remove eBPF interfaces

[Alexei Starovoitov]

On Tue, Mar 29, 2022 at 10:30 AM Beau Belgrave
<beaub@linux.microsoft.com> wrote:
>
> Remove eBPF interfaces within user_events to ensure they are fully
> reviewed.
>
> Link: https://lore.kernel.org/all/20220329165718.GA10381@kbox/
>
> Signed-off-by: Beau Belgrave <beaub@linux.microsoft.com>

Thanks for the quick revert.

Steven,

since you've applied the initial set please take this one and
send pull req to Linus asap.

Thanks

Re: [PATCH] tracing/user_events: Remove eBPF interfaces

[Steven Rostedt]

On Tue, 29 Mar 2022 11:19:05 -0700
Alexei Starovoitov <alexei.starovoitov@gmail.com> wrote:

> On Tue, Mar 29, 2022 at 10:30 AM Beau Belgrave
> <beaub@linux.microsoft.com> wrote:
> >
> > Remove eBPF interfaces within user_events to ensure they are fully
> > reviewed.
> >
> > Link: https://lore.kernel.org/all/20220329165718.GA10381@kbox/
> >
> > Signed-off-by: Beau Belgrave <beaub@linux.microsoft.com>  
> 
> Thanks for the quick revert.
> 
> Steven,
> 
> since you've applied the initial set please take this one and
> send pull req to Linus asap.
> 

Relax Alexei,

I'll send it to Linus after it goes through my testing process with all my
other patches in queue. An ABI is only defined by the main release "5.18"
and not the rc releases (like 5.18-rc1). But it will definitely be gone
before rc2.

-- Steve