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linux/kernel/trace/trace_synth.h

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// SPDX-License-Identifier: GPL-2.0
#ifndef __TRACE_SYNTH_H
#define __TRACE_SYNTH_H
#include "trace_dynevent.h"
#define SYNTH_SYSTEM "synthetic"
#define SYNTH_FIELDS_MAX 64
#define STR_VAR_LEN_MAX MAX_FILTER_STR_VAL /* must be multiple of sizeof(u64) */
struct synth_field {
char *type;
char *name;
size_t size;
unsigned int offset;
tracing: Synthetic event field_pos is an index not a boolean Performing the following: ># echo 'wakeup_lat s32 pid; u64 delta; char wake_comm[]' > synthetic_events ># echo 'hist:keys=pid:__arg__1=common_timestamp.usecs' > events/sched/sched_waking/trigger ># echo 'hist:keys=next_pid:pid=next_pid,delta=common_timestamp.usecs-$__arg__1:onmatch(sched.sched_waking).trace(wakeup_lat,$pid,$delta,prev_comm)'\ > events/sched/sched_switch/trigger ># echo 1 > events/synthetic/enable Crashed the kernel: BUG: kernel NULL pointer dereference, address: 000000000000001b #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 0 P4D 0 Oops: 0000 [#1] PREEMPT SMP CPU: 7 PID: 0 Comm: swapper/7 Not tainted 5.13.0-rc5-test+ #104 Hardware name: Hewlett-Packard HP Compaq Pro 6300 SFF/339A, BIOS K01 v03.03 07/14/2016 RIP: 0010:strlen+0x0/0x20 Code: f6 82 80 2b 0b bc 20 74 11 0f b6 50 01 48 83 c0 01 f6 82 80 2b 0b bc 20 75 ef c3 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 <80> 3f 00 74 10 48 89 f8 48 83 c0 01 80 38 9 f8 c3 31 RSP: 0018:ffffaa75000d79d0 EFLAGS: 00010046 RAX: 0000000000000002 RBX: ffff9cdb55575270 RCX: 0000000000000000 RDX: ffff9cdb58c7a320 RSI: ffffaa75000d7b40 RDI: 000000000000001b RBP: ffffaa75000d7b40 R08: ffff9cdb40a4f010 R09: ffffaa75000d7ab8 R10: ffff9cdb4398c700 R11: 0000000000000008 R12: ffff9cdb58c7a320 R13: ffff9cdb55575270 R14: ffff9cdb58c7a000 R15: 0000000000000018 FS: 0000000000000000(0000) GS:ffff9cdb5aa00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000000000000001b CR3: 00000000c0612006 CR4: 00000000001706e0 Call Trace: trace_event_raw_event_synth+0x90/0x1d0 action_trace+0x5b/0x70 event_hist_trigger+0x4bd/0x4e0 ? cpumask_next_and+0x20/0x30 ? update_sd_lb_stats.constprop.0+0xf6/0x840 ? __lock_acquire.constprop.0+0x125/0x550 ? find_held_lock+0x32/0x90 ? sched_clock_cpu+0xe/0xd0 ? lock_release+0x155/0x440 ? update_load_avg+0x8c/0x6f0 ? enqueue_entity+0x18a/0x920 ? __rb_reserve_next+0xe5/0x460 ? ring_buffer_lock_reserve+0x12a/0x3f0 event_triggers_call+0x52/0xe0 trace_event_buffer_commit+0x1ae/0x240 trace_event_raw_event_sched_switch+0x114/0x170 __traceiter_sched_switch+0x39/0x50 __schedule+0x431/0xb00 schedule_idle+0x28/0x40 do_idle+0x198/0x2e0 cpu_startup_entry+0x19/0x20 secondary_startup_64_no_verify+0xc2/0xcb The reason is that the dynamic events array keeps track of the field position of the fields array, via the field_pos variable in the synth_field structure. Unfortunately, that field is a boolean for some reason, which means any field_pos greater than 1 will be a bug (in this case it was 2). Link: https://lkml.kernel.org/r/20210721191008.638bce34@oasis.local.home Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Ingo Molnar <mingo@kernel.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: stable@vger.kernel.org Fixes: bd82631d7ccdc ("tracing: Add support for dynamic strings to synthetic events") Reviewed-by: Tom Zanussi <zanussi@kernel.org> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
2021-07-21 16:10:08 -07:00
unsigned int field_pos;
bool is_signed;
bool is_string;
tracing: Add support for dynamic strings to synthetic events Currently, sythetic events only support static string fields such as: # echo 'test_latency u64 lat; char somename[32]' > /sys/kernel/debug/tracing/synthetic_events Which is fine, but wastes a lot of space in the event. It also prevents the most commonly-defined strings in the existing trace events e.g. those defined using __string(), from being passed to synthetic events via the trace() action. With this change, synthetic events with dynamic fields can be defined: # echo 'test_latency u64 lat; char somename[]' > /sys/kernel/debug/tracing/synthetic_events And the trace() action can be used to generate events using either dynamic or static strings: # echo 'hist:keys=name:lat=common_timestamp.usecs-$ts0:onmatch(sys.event).test_latency($lat,name)' > /sys/kernel/debug/tracing/events The synthetic event dynamic strings are implemented in the same way as the existing __data_loc strings and appear as such in the format file. [ <rostedt@goodmis.org>: added __set_synth_event_print_fmt() changes: I added the following to make it work with trace-cmd. Dynamic strings must have __get_str() for events in the print_fmt otherwise it can't be parsed correctly. ] Link: https://lore.kernel.org/r/cover.1601588066.git.zanussi@kernel.org Link: https://lkml.kernel.org/r/3ed35b6d0e390f5b94cb4a9ba1cc18f5982ab277.1601848695.git.zanussi@kernel.org Tested-by: Axel Rasmussen <axelrasmussen@google.com> Signed-off-by: Tom Zanussi <zanussi@kernel.org> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
2020-10-04 15:14:06 -07:00
bool is_dynamic;
tracing: Allow synthetic events to pass around stacktraces Allow a stacktrace from one event to be displayed by the end event of a synthetic event. This is very useful when looking for the longest latency of a sleep or something blocked on I/O. # cd /sys/kernel/tracing/ # echo 's:block_lat pid_t pid; u64 delta; unsigned long[] stack;' > dynamic_events # echo 'hist:keys=next_pid:ts=common_timestamp.usecs,st=stacktrace if prev_state == 1||prev_state == 2' > events/sched/sched_switch/trigger # echo 'hist:keys=prev_pid:delta=common_timestamp.usecs-$ts,s=$st:onmax($delta).trace(block_lat,prev_pid,$delta,$s)' >> events/sched/sched_switch/trigger The above creates a "block_lat" synthetic event that take the stacktrace of when a task schedules out in either the interruptible or uninterruptible states, and on a new per process max $delta (the time it was scheduled out), will print the process id and the stacktrace. # echo 1 > events/synthetic/block_lat/enable # cat trace # TASK-PID CPU# ||||| TIMESTAMP FUNCTION # | | | ||||| | | kworker/u16:0-767 [006] d..4. 560.645045: block_lat: pid=767 delta=66 stack=STACK: => __schedule => schedule => pipe_read => vfs_read => ksys_read => do_syscall_64 => 0x966000aa <idle>-0 [003] d..4. 561.132117: block_lat: pid=0 delta=413787 stack=STACK: => __schedule => schedule => schedule_hrtimeout_range_clock => do_sys_poll => __x64_sys_poll => do_syscall_64 => 0x966000aa <...>-153 [006] d..4. 562.068407: block_lat: pid=153 delta=54 stack=STACK: => __schedule => schedule => io_schedule => rq_qos_wait => wbt_wait => __rq_qos_throttle => blk_mq_submit_bio => submit_bio_noacct_nocheck => ext4_bio_write_page => mpage_submit_page => mpage_process_page_bufs => mpage_prepare_extent_to_map => ext4_do_writepages => ext4_writepages => do_writepages => __writeback_single_inode Link: https://lkml.kernel.org/r/20230117152236.010941267@goodmis.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Tom Zanussi <zanussi@kernel.org> Cc: Ross Zwisler <zwisler@google.com> Cc: Ching-lin Yu <chinglinyu@google.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
2023-01-17 08:21:28 -07:00
bool is_stack;
};
struct synth_event {
struct dyn_event devent;
int ref;
char *name;
struct synth_field **fields;
unsigned int n_fields;
tracing: Add support for dynamic strings to synthetic events Currently, sythetic events only support static string fields such as: # echo 'test_latency u64 lat; char somename[32]' > /sys/kernel/debug/tracing/synthetic_events Which is fine, but wastes a lot of space in the event. It also prevents the most commonly-defined strings in the existing trace events e.g. those defined using __string(), from being passed to synthetic events via the trace() action. With this change, synthetic events with dynamic fields can be defined: # echo 'test_latency u64 lat; char somename[]' > /sys/kernel/debug/tracing/synthetic_events And the trace() action can be used to generate events using either dynamic or static strings: # echo 'hist:keys=name:lat=common_timestamp.usecs-$ts0:onmatch(sys.event).test_latency($lat,name)' > /sys/kernel/debug/tracing/events The synthetic event dynamic strings are implemented in the same way as the existing __data_loc strings and appear as such in the format file. [ <rostedt@goodmis.org>: added __set_synth_event_print_fmt() changes: I added the following to make it work with trace-cmd. Dynamic strings must have __get_str() for events in the print_fmt otherwise it can't be parsed correctly. ] Link: https://lore.kernel.org/r/cover.1601588066.git.zanussi@kernel.org Link: https://lkml.kernel.org/r/3ed35b6d0e390f5b94cb4a9ba1cc18f5982ab277.1601848695.git.zanussi@kernel.org Tested-by: Axel Rasmussen <axelrasmussen@google.com> Signed-off-by: Tom Zanussi <zanussi@kernel.org> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
2020-10-04 15:14:06 -07:00
struct synth_field **dynamic_fields;
unsigned int n_dynamic_fields;
unsigned int n_u64;
struct trace_event_class class;
struct trace_event_call call;
struct tracepoint *tp;
struct module *mod;
};
extern struct synth_event *find_synth_event(const char *name);
#endif /* __TRACE_SYNTH_H */