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linux/kernel/trace
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Steven Rostedt 299ea67e6a tracing: Add a config and syscall_user_buf_size file to limit amount written 
When a system call that can copy user space addresses into the ring
buffer, it can copy up to 511 bytes of data. This can waste precious ring
buffer space if the user isn't interested in the output. Add a new file
"syscall_user_buf_size" that gets initialized to a new config
CONFIG_SYSCALL_BUF_SIZE_DEFAULT that defaults to 63.

The config also is used to limit how much perf can read from user space.

Also lower the max down to 165, as this isn't to record everything that a
system call may be passing through to the kernel. 165 is more than enough.

The reason for 165 is because adding one for the nul terminating byte, as
well as possibly needing to append the "..." string turns it into 170
bytes. As this needs to save up to 3 arguments and 3 * 170 is 510 which
fits nicely in 512 bytes (a power of 2).

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Takaya Saeki <takayas@google.com>
Cc: Tom Zanussi <zanussi@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ian Rogers <irogers@google.com>
Cc: Douglas Raillard <douglas.raillard@arm.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Link: https://lore.kernel.org/20251028231148.260068913@kernel.org
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
2025-10-28 20:10:59 -04:00
..
rv rv: Make rtapp/pagefault monitor depends on CONFIG_MMU 2025-10-20 12:47:40 +02:00
blktrace.c Significant patch series in this pull request: 2025-08-03 16:23:09 -07:00
bpf_trace.c file->f_path constification 2025-10-03 16:32:36 -07:00
bpf_trace.h tracing/treewide: Remove second parameter of __assign_str() 2024-05-22 20:14:47 -04:00
error_report-traces.c
fgraph.c tracing: fgraph: Protect return handler from recursion loop 2025-09-27 09:04:05 -04:00
fprobe.c tracing: fprobe: Fix to remove recorded module addresses from filter 2025-09-24 23:18:26 +09:00
ftrace.c ftrace: Fix softlockup in ftrace_module_enable 2025-09-30 17:27:58 -04:00
ftrace_internal.h function_graph: Make fgraph_update_pid_func() a stub for !DYNAMIC_FTRACE 2024-06-10 18:08:23 -04:00
Kconfig tracing: Add a config and syscall_user_buf_size file to limit amount written 2025-10-28 20:10:59 -04:00
kprobe_event_gen_test.c
Makefile tracing: Have eprobes have their own config option 2025-07-30 10:38:43 -04:00
pid_list.c tracing: Cleanup upper_empty() in pid_list 2025-05-14 11:19:32 -04:00
pid_list.h
power-traces.c PM: cpufreq: powernv/tracing: Move powernv_throttle trace event 2025-07-21 16:40:56 -04:00
preemptirq_delay_test.c kernel: trace: preemptirq_delay_test: use offstack cpu mask 2025-07-08 18:17:38 -04:00
rethook.c rethook: honor CONFIG_FTRACE_VALIDATE_RCU_IS_WATCHING in rethook_try_get() 2024-05-01 23:18:48 +09:00
ring_buffer.c ring buffer: Propagate __rb_map_vma return value to caller 2025-10-08 21:48:58 -04:00
ring_buffer_benchmark.c ring-buffer: Use str_low_high() helper in ring_buffer_producer() 2024-10-19 11:12:25 -04:00
rpm-traces.c
synth_event_gen_test.c tracing / synthetic: Disable events after testing in synth_event_gen_test_init() 2023-12-21 10:04:45 -05:00
trace.c tracing: Add a config and syscall_user_buf_size file to limit amount written 2025-10-28 20:10:59 -04:00
trace.h tracing: Add a config and syscall_user_buf_size file to limit amount written 2025-10-28 20:10:59 -04:00
trace_benchmark.c tracing: Improve benchmark test performance by using do_div() 2024-05-13 20:00:57 -04:00
trace_benchmark.h
trace_boot.c tracing: Allow creating instances with specified system events 2023-12-18 23:14:16 -05:00
trace_branch.c tracing: branch: Use trace_tracing_is_on_cpu() instead of "disabled" field 2025-05-09 15:19:10 -04:00
trace_btf.c tracing/probes: Fix to search structure fields correctly 2024-02-17 21:25:42 +09:00
trace_btf.h tracing/probes: Add a function to search a member of a struct/union 2023-08-23 09:40:16 +09:00
trace_clock.c tracing: Use atomic64_inc_return() in trace_clock_counter() 2024-10-09 19:59:49 -04:00
trace_dynevent.c tracing: dynevent: Add a missing lockdown check on dynevent 2025-09-25 00:22:46 +09:00
trace_dynevent.h tracing: probes: Fix a possible race in trace_probe_log APIs 2025-05-13 22:23:34 +09:00
trace_entries.h ftrace: Expose call graph depth as unsigned int 2025-05-08 09:36:08 -04:00
trace_eprobe.c tracing: Have eprobes handle arrays 2025-07-24 22:57:32 +09:00
trace_event_perf.c perf: Remove unnecessary parameter of security check 2025-02-26 14:13:58 -05:00
trace_events.c tracing: Fix lock imbalance in s_start() memory allocation failure path 2025-10-03 12:13:12 -04:00
trace_events_filter.c tracing changes for 6.17 2025-08-01 10:29:36 -07:00
trace_events_filter_test.h
trace_events_hist.c tracing: Rename event_trigger_alloc() to trigger_data_alloc() 2025-05-09 15:19:11 -04:00
trace_events_inject.c tracing: Have format file honor EVENT_FILE_FL_FREED 2024-08-07 18:12:46 -04:00
trace_events_synth.c tracing: Add guard(ring_buffer_nest) 2025-08-01 16:49:15 -04:00
trace_events_trigger.c tracing updates for v6.16: 2025-05-29 21:04:36 -07:00
trace_events_user.c tracing updates for v6.18: 2025-10-05 09:43:36 -07:00
trace_export.c tracing: Add back FORTIFY_SOURCE logic to kernel_stack event structure 2023-07-30 18:11:44 -04:00
trace_fprobe.c tracing: Fix race condition in kprobe initialization causing NULL pointer dereference 2025-10-02 08:05:01 +09:00
trace_functions.c tracing updates for v6.16: 2025-05-29 21:04:36 -07:00
trace_functions_graph.c fgraph: Copy args in intermediate storage with entry 2025-08-22 17:32:35 -04:00
trace_hwlat.c tracing: Replace opencoded cpumask_next_wrap() in move_to_next_cpu() 2025-07-08 18:17:29 -04:00
trace_irqsoff.c tracing: Fix irqoff tracers on failure of acquiring calltime 2025-10-08 12:10:44 -04:00
trace_kdb.c ring-buffer: Remove ring_buffer_read_prepare_sync() 2025-07-22 20:01:41 -04:00
trace_kprobe.c tracing: Fix race condition in kprobe initialization causing NULL pointer dereference 2025-10-02 08:05:01 +09:00
trace_kprobe_selftest.c tracing: arm64: Avoid missing-prototype warnings 2023-07-12 12:06:04 -04:00
trace_kprobe_selftest.h
trace_mmiotrace.c tracing/mmiotrace: Remove reference to unused per CPU data pointer 2025-05-08 09:36:09 -04:00
trace_nop.c
trace_osnoise.c tracing clean up and fixes for v6.18: 2025-10-09 12:18:22 -07:00
trace_output.c tracing: Have unsigned int function args displayed as hexadecimal 2025-08-01 19:14:51 -04:00
trace_output.h ftrace: Add print_function_args() 2025-03-04 11:27:23 -05:00
trace_preemptirq.c tracing: Fix archs that still call tracepoints without RCU watching 2024-12-05 09:28:58 -05:00
trace_printk.c
trace_probe.c Probes updates for v6.17: 2025-07-30 15:38:01 -07:00
trace_probe.h tracing: Fix race condition in kprobe initialization causing NULL pointer dereference 2025-10-02 08:05:01 +09:00
trace_probe_kernel.h tracing/probes: Fix to record 0-length data_loc in fetch_store_string*() if fails 2023-07-14 17:04:58 +09:00
trace_probe_tmpl.h tracing/fprobe: Enable fprobe events with CONFIG_DYNAMIC_FTRACE_WITH_ARGS 2024-12-26 10:50:04 -05:00
trace_recursion_record.c
trace_sched_switch.c tracing: Ensure optimized hashing works 2025-09-30 17:27:58 -04:00
trace_sched_wakeup.c tracing: Fix wakeup tracers on failure of acquiring calltime 2025-10-08 12:10:26 -04:00
trace_selftest.c fgraph: Pass ftrace_regs to retfunc 2024-12-26 10:50:03 -05:00
trace_selftest_dynamic.c
trace_seq.c trace_seq: Increase the buffer size to almost two pages 2023-12-18 23:14:16 -05:00
trace_stack.c tracing updates for v6.16: 2025-05-29 21:04:36 -07:00
trace_stat.c tracing: Switch trace_stat.c code over to use guard() 2024-12-26 10:38:37 -05:00
trace_stat.h
trace_synth.h
trace_syscalls.c tracing: Add a config and syscall_user_buf_size file to limit amount written 2025-10-28 20:10:59 -04:00
trace_uprobe.c tracing: Fix race condition in kprobe initialization causing NULL pointer dereference 2025-10-02 08:05:01 +09:00
tracing_map.c tracing: Use vmalloc_array() to improve code 2025-09-23 09:31:58 -04:00
tracing_map.h tracing: Remove unused extern declaration tracing_map_set_field_descr() 2023-07-23 11:08:14 -04:00