tracing/osnoise: Fix resetting of tracepoints

In the Linux kernel, the following vulnerability has been resolved:

tracing/osnoise: Fix resetting of tracepoints

If a timerlat tracer is started with the osnoise option OSNOISE_WORKLOAD
disabled, but then that option is enabled and timerlat is removed, the
tracepoints that were enabled on timerlat registration do not get
disabled. If the option is disabled again and timelat is started, then it
triggers a warning in the tracepoint code due to registering the
tracepoint again without ever disabling it.

Do not use the same user space defined options to know to disable the
tracepoints when timerlat is removed. Instead, set a global flag when it
is enabled and use that flag to know to disable the events.

~# echo NO_OSNOISE_WORKLOAD > /sys/kernel/tracing/osnoise/options
~# echo timerlat > /sys/kernel/tracing/current_tracer
~# echo OSNOISE_WORKLOAD > /sys/kernel/tracing/osnoise/options
~# echo nop > /sys/kernel/tracing/current_tracer
~# echo NO_OSNOISE_WORKLOAD > /sys/kernel/tracing/osnoise/options
~# echo timerlat > /sys/kernel/tracing/current_tracer

Triggers:

------------[ cut here ]------------
WARNING: CPU: 6 PID: 1337 at kernel/tracepoint.c:294 tracepoint_add_func+0x3b6/0x3f0
Modules linked in:
CPU: 6 UID: 0 PID: 1337 Comm: rtla Not tainted 6.13.0-rc4-test-00018-ga867c441128e-dirty #73
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:tracepoint_add_func+0x3b6/0x3f0
Code: 48 8b 53 28 48 8b 73 20 4c 89 04 24 e8 23 59 11 00 4c 8b 04 24 e9 36 fe ff ff 0f 0b b8 ea ff ff ff 45 84 e4 0f 84 68 fe ff ff <0f> 0b e9 61 fe ff ff 48 8b 7b 18 48 85 ff 0f 84 4f ff ff ff 49 8b
RSP: 0018:ffffb9b003a87ca0 EFLAGS: 00010202
RAX: 00000000ffffffef RBX: ffffffff92f30860 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffff9bf59e91ccd0 RDI: ffffffff913b6410
RBP: 000000000000000a R08: 00000000000005c7 R09: 0000000000000002
R10: ffffb9b003a87ce0 R11: 0000000000000002 R12: 0000000000000001
R13: ffffb9b003a87ce0 R14: ffffffffffffffef R15: 0000000000000008
FS: 00007fce81209240(0000) GS:ffff9bf6fdd00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055e99b728000 CR3: 00000001277c0002 CR4: 0000000000172ef0
Call Trace:
<TASK>
? __warn.cold+0xb7/0x14d
? tracepoint_add_func+0x3b6/0x3f0
? report_bug+0xea/0x170
? handle_bug+0x58/0x90
? exc_invalid_op+0x17/0x70
? asm_exc_invalid_op+0x1a/0x20
? __pfx_trace_sched_migrate_callback+0x10/0x10
? tracepoint_add_func+0x3b6/0x3f0
? __pfx_trace_sched_migrate_callback+0x10/0x10
? __pfx_trace_sched_migrate_callback+0x10/0x10
tracepoint_probe_register+0x78/0xb0
? __pfx_trace_sched_migrate_callback+0x10/0x10
osnoise_workload_start+0x2b5/0x370
timerlat_tracer_init+0x76/0x1b0
tracing_set_tracer+0x244/0x400
tracing_set_trace_write+0xa0/0xe0
vfs_write+0xfc/0x570
? do_sys_openat2+0x9c/0xe0
ksys_write+0x72/0xf0
do_syscall_64+0x79/0x1c0
entry_SYSCALL_64_after_hwframe+0x76/0x7e