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Yonghong Song 8b401f9ed2 bpf: implement bpf_send_signal() helper 
This patch tries to solve the following specific use case.

Currently, bpf program can already collect stack traces
through kernel function get_perf_callchain()
when certain events happens (e.g., cache miss counter or
cpu clock counter overflows). But such stack traces are
not enough for jitted programs, e.g., hhvm (jited php).
To get real stack trace, jit engine internal data structures
need to be traversed in order to get the real user functions.

bpf program itself may not be the best place to traverse
the jit engine as the traversing logic could be complex and
it is not a stable interface either.

Instead, hhvm implements a signal handler,
e.g. for SIGALARM, and a set of program locations which
it can dump stack traces. When it receives a signal, it will
dump the stack in next such program location.

Such a mechanism can be implemented in the following way:
  . a perf ring buffer is created between bpf program
    and tracing app.
  . once a particular event happens, bpf program writes
    to the ring buffer and the tracing app gets notified.
  . the tracing app sends a signal SIGALARM to the hhvm.

But this method could have large delays and causing profiling
results skewed.

This patch implements bpf_send_signal() helper to send
a signal to hhvm in real time, resulting in intended stack traces.

Acked-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
 		2019-05-24 23:26:47 +02:00
..
Kconfig treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
Makefile tracing: Add unified dynamic event framework 2018-12-08 20:54:09 -05:00
blktrace.c blkcg: annotate implicit fall through 2019-03-13 14:31:12 -06:00
bpf_trace.c bpf: implement bpf_send_signal() helper 2019-05-24 23:26:47 +02:00
fgraph.c tracing: Fix ftrace_graph_get_ret_stack() to use task and not current 2018-12-22 08:21:03 -05:00
ftrace.c The major changes in this tracing update includes: 2019-05-15 16:05:47 -07:00
ftrace_internal.h ftrace: Create new ftrace_internal.h header 2018-12-08 20:54:06 -05:00
power-traces.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
preemptirq_delay_test.c tracing: Use trace_clock_local() for looping in preemptirq_delay_test.c 2018-10-17 15:35:33 -04:00
ring_buffer.c The major changes in this tracing update includes: 2019-05-15 16:05:47 -07:00
ring_buffer_benchmark.c ring-buffer: Fix mispelling of Calculate 2019-05-08 12:15:12 -04:00
rpm-traces.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
trace.c The major changes in this tracing update includes: 2019-05-15 16:05:47 -07:00
trace.h The major changes in this tracing update includes: 2019-05-15 16:05:47 -07:00
trace_benchmark.c rcu: Rename cond_resched_rcu_qs() to cond_resched_tasks_rcu_qs() 2018-05-15 10:27:29 -07:00
trace_benchmark.h tracing: Fix SPDX format headers to use C++ style comments 2018-08-16 19:08:06 -04:00
trace_branch.c x86/uaccess, ftrace: Fix ftrace_likely_update() vs. SMAP 2019-04-03 11:02:24 +02:00
trace_clock.c tracing: Add SPDX License format tags to tracing files 2018-08-16 19:08:06 -04:00
trace_dynevent.c tracing: initialize variable in create_dyn_event() 2019-03-26 08:35:36 -04:00
trace_dynevent.h tracing: Add unified dynamic event framework 2018-12-08 20:54:09 -05:00
trace_entries.h tracing: Change the function format to display function names by perf 2019-02-11 14:53:43 -05:00
trace_event_perf.c tracing/perf: Use strndup_user() instead of buggy open-coded version 2019-02-21 10:35:10 -05:00
trace_events.c tracing: Fix partial reading of trace event's id file 2019-05-08 12:15:12 -04:00
trace_events_filter.c tracing: Fix white space issues in parse_pred() function 2019-05-08 12:15:12 -04:00
trace_events_filter_test.h tracing: Fix SPDX format headers to use C++ style comments 2018-08-16 19:08:06 -04:00
trace_events_hist.c The major changes in this tracing update includes: 2019-05-15 16:05:47 -07:00
trace_events_trigger.c tracing: Add trace_array parameter to create_event_filter() 2019-04-08 09:22:28 -04:00
trace_export.c tracing: Add trigger file for trace_markers tracefs/ftrace/print 2018-05-29 08:28:53 -04:00
trace_functions.c tracing: Update stack trace skipping for ORC unwinder 2018-01-23 15:57:00 -05:00
trace_functions_graph.c tracing: Put a margin between flags and duration for wakeup tracers 2019-02-06 11:56:19 -05:00
trace_hwlat.c tracing: Add SPDX License format tags to tracing files 2018-08-16 19:08:06 -04:00
trace_irqsoff.c The biggest change for this release is in the histogram code. 2019-03-11 17:01:32 -07:00
trace_kdb.c tracing: kdb: Allow ftdump to skip all but the last few entries 2019-05-02 21:32:55 -04:00
trace_kprobe.c tracing: Use tracing error_log with probe events 2019-04-02 18:24:07 -04:00
trace_kprobe_selftest.c selftest/ftrace: Move kprobe selftest function to separate compile unit 2018-07-30 18:41:04 -04:00
trace_kprobe_selftest.h tracing: Fix SPDX format headers to use C++ style comments 2018-08-16 19:08:06 -04:00
trace_mmiotrace.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
trace_nop.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
trace_output.c tracing: Simplify printf'ing in seq_print_sym 2018-12-22 08:21:06 -05:00
trace_output.h tracing: Fix SPDX format headers to use C++ style comments 2018-08-16 19:08:06 -04:00
trace_preemptirq.c kprobes: Prohibit probing on hardirq tracers 2019-02-13 08:16:40 +01:00
trace_printk.c tracing: Trivia spelling fix containerof() -> container_of() 2018-09-26 12:21:00 +03:00
trace_probe.c tracing: Replace kzalloc with kcalloc 2019-05-08 12:15:12 -04:00
trace_probe.h tracing: uprobes: Re-enable $comm support for uprobe events 2019-05-08 12:15:11 -04:00
trace_probe_tmpl.h tracing: probeevent: Do not accumulate on ret variable 2019-05-08 12:15:11 -04:00
trace_sched_switch.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
trace_sched_wakeup.c tracing: Add conditional snapshot 2019-02-20 13:51:06 -05:00
trace_selftest.c function_graph: Have selftest also emulate tr->reset() as it did with tr->init() 2019-04-21 19:46:56 -04:00
trace_selftest_dynamic.c ftrace: Mark function tracer test functions noinline/noclone 2018-01-23 15:57:29 -05:00
trace_seq.c tracing: Add SPDX License format tags to tracing files 2018-08-16 19:08:06 -04:00
trace_stack.c tracing: Remove the last struct stack_trace usage 2019-04-29 12:37:56 +02:00
trace_stat.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
trace_stat.h tracing: Fix SPDX format headers to use C++ style comments 2018-08-16 19:08:06 -04:00
trace_syscalls.c syscalls: Remove start and number from syscall_get_arguments() args 2019-04-05 09:26:43 -04:00
trace_uprobe.c tracing: uprobes: Re-enable $comm support for uprobe events 2019-05-08 12:15:11 -04:00
tracing_map.c tracing: Add SPDX License format tags to tracing files 2018-08-16 19:08:06 -04:00
tracing_map.h tracing: Fix SPDX format headers to use C++ style comments 2018-08-16 19:08:06 -04:00