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When an event probe is to be removed via the API that created it via the
dynamic events, an -ENOENT error is returned.
This is because the removal of the event probe does not expect to see the
event system and name that the event probe is attached to, even though
that's part of the API to create it. As the removal of probes is to use
the same API as they are created.
In fact, the removal is not consistent with the kprobes and uprobes
removal. Fix that by allowing various ways to remove the eprobe.
The eprobe is created with:
e:[GROUP/]NAME SYSTEM/EVENT [OPTIONS]
Have it get removed by echoing in the following into dynamic_events:
# Remove all eprobes with NAME
echo '-:NAME' >> dynamic_events
# Remove a specific eprobe
echo '-:GROUP/NAME' >> dynamic_events
echo '-:GROUP/NAME SYSTEM/EVENT' >> dynamic_events
echo '-:NAME SYSTEM/EVENT' >> dynamic_events
echo '-:GROUP/NAME SYSTEM/EVENT OPTIONS' >> dynamic_events
echo '-:NAME SYSTEM/EVENT OPTIONS' >> dynamic_events
Link: https://lkml.kernel.org/r/20211012081925.0e19cc4f@gandalf.local.home
Link: https://lkml.kernel.org/r/20211013205533.630722129@goodmis.org
Suggested-by: Masami Hiramatsu <mhiramat@kernel.org>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Fixes: 7491e2c442781 ("tracing: Add a probe that attaches to trace events")
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
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kmemleak report:
unreferenced object 0xffff900a70ec7ec0 (size 32):
comm "ftracetest", pid 2770, jiffies 4295042510 (age 311.464s)
hex dump (first 32 bytes):
c8 31 23 45 0a 90 ff ff 40 85 c7 6e 0a 90 ff ff .1#E....@..n....
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
backtrace:
[<000000009d3751fd>] kmem_cache_alloc_trace+0x2a2/0x440
[<0000000088b8124b>] eprobe_register+0x1e3/0x350
[<000000002a9a0517>] __ftrace_event_enable_disable+0x7c/0x240
[<0000000019109321>] event_enable_write+0x93/0xe0
[<000000007d85b320>] vfs_write+0xb9/0x260
[<00000000b94c5e41>] ksys_write+0x67/0xe0
[<000000005a08c81d>] __x64_sys_write+0x1a/0x20
[<00000000240bf576>] do_syscall_64+0x3b/0xc0
[<0000000043d5d9f6>] entry_SYSCALL_64_after_hwframe+0x44/0xae
unreferenced object 0xffff900a56bbf280 (size 128):
comm "ftracetest", pid 2770, jiffies 4295042510 (age 311.464s)
hex dump (first 32 bytes):
ff ff ff ff ff ff ff ff 00 00 00 00 01 00 00 00 ................
80 69 3b b2 ff ff ff ff 20 69 3b b2 ff ff ff ff .i;..... i;.....
backtrace:
[<000000009d3751fd>] kmem_cache_alloc_trace+0x2a2/0x440
[<00000000c4e90fad>] eprobe_register+0x1fc/0x350
[<000000002a9a0517>] __ftrace_event_enable_disable+0x7c/0x240
[<0000000019109321>] event_enable_write+0x93/0xe0
[<000000007d85b320>] vfs_write+0xb9/0x260
[<00000000b94c5e41>] ksys_write+0x67/0xe0
[<000000005a08c81d>] __x64_sys_write+0x1a/0x20
[<00000000240bf576>] do_syscall_64+0x3b/0xc0
[<0000000043d5d9f6>] entry_SYSCALL_64_after_hwframe+0x44/0xae
In new_eprobe_trigger(), allocated edata and trigger variables are
never freed.
To fix, free memory in disable_eprobe().
Link: https://lkml.kernel.org/r/20211008071802.GA2098@cosmos
Fixes: 7491e2c442781 ("tracing: Add a probe that attaches to trace events")
Signed-off-by: Vamshi K Sthambamkadi <vamshi.k.sthambamkadi@gmail.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
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There are two bugs in this code. First, if the kzalloc() fails it leads
to a NULL dereference of "ep" on the next line. Second, if the
alloc_event_probe() function returns an error then it leads to an
error pointer dereference in the caller.
Link: https://lkml.kernel.org/r/20210824115150.GI31143@kili
Fixes: 7491e2c44278 ("tracing: Add a probe that attaches to trace events")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
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A new dynamic event is introduced: event probe. The event is attached
to an existing tracepoint and uses its fields as arguments. The user
can specify custom format string of the new event, select what tracepoint
arguments will be printed and how to print them.
An event probe is created by writing configuration string in
'dynamic_events' ftrace file:
e[:[SNAME/]ENAME] SYSTEM/EVENT [FETCHARGS] - Set an event probe
-:SNAME/ENAME - Delete an event probe
Where:
SNAME - System name, if omitted 'eprobes' is used.
ENAME - Name of the new event in SNAME, if omitted the SYSTEM_EVENT is used.
SYSTEM - Name of the system, where the tracepoint is defined, mandatory.
EVENT - Name of the tracepoint event in SYSTEM, mandatory.
FETCHARGS - Arguments:
<name>=$<field>[:TYPE] - Fetch given filed of the tracepoint and print
it as given TYPE with given name. Supported
types are:
(u8/u16/u32/u64/s8/s16/s32/s64), basic type
(x8/x16/x32/x64), hexadecimal types
"string", "ustring" and bitfield.
Example, attach an event probe on openat system call and print name of the
file that will be opened:
echo "e:esys/eopen syscalls/sys_enter_openat file=\$filename:string" >> dynamic_events
A new dynamic event is created in events/esys/eopen/ directory. It
can be deleted with:
echo "-:esys/eopen" >> dynamic_events
Filters, triggers and histograms can be attached to the new event, it can
be matched in synthetic events. There is one limitation - an event probe
can not be attached to kprobe, uprobe or another event probe.
Link: https://lkml.kernel.org/r/20210812145805.2292326-1-tz.stoyanov@gmail.com
Link: https://lkml.kernel.org/r/20210819152825.142428383@goodmis.org
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Co-developed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
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