tracing: Add fprobe/tracepoint events #5090
Closed
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
![kernel-patches-daemon-bpf[bot]](https://avatars.githubusercontent.com/u/70728002?s=60&v=4){kind=small}
Pass return address as 'ret_ip' to the fprobe entry and return handlers so that the fprobe user handler can get the reutrn address without analyzing arch-dependent pt_regs. Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Add fprobe events for tracing function entry and exit instead of kprobe
events. With this change, we can continue to trace function entry/exit
even if the CONFIG_KPROBES_ON_FTRACE is not available. Since
CONFIG_KPROBES_ON_FTRACE requires the CONFIG_DYNAMIC_FTRACE_WITH_REGS,
it is not available if the architecture only supports
CONFIG_DYNAMIC_FTRACE_WITH_ARGS. And that means kprobe events can not
probe function entry/exit effectively on such architecture.
But this can be solved if the dynamic events supports fprobe events.
The fprobe event is a new dynamic events which is only for the function
(symbol) entry and exit. This event accepts non register fetch arguments
so that user can trace the function arguments and return values.
The fprobe events syntax is here;
f[:[GRP/][EVENT]] FUNCTION [FETCHARGS]
f[MAXACTIVE][:[GRP/][EVENT]] FUNCTION%return [FETCHARGS]
E.g.
# echo 'f vfs_read $arg1' >> dynamic_events
# echo 'f vfs_read%return $retval' >> dynamic_events
# cat dynamic_events
f:fprobes/vfs_read__entry vfs_read arg1=$arg1
f:fprobes/vfs_read__exit vfs_read%return arg1=$retval
# echo 1 > events/fprobes/enable
# head -n 20 trace | tail
# TASK-PID CPU# ||||| TIMESTAMP FUNCTION
# | | | ||||| | |
sh-142 [005] ...1. 448.386420: vfs_read__entry: (vfs_read+0x4/0x340) arg1=0xffff888007f7c540
sh-142 [005] ..... 448.386436: vfs_read__exit: (ksys_read+0x75/0x100 <- vfs_read) arg1=0x1
sh-142 [005] ...1. 448.386451: vfs_read__entry: (vfs_read+0x4/0x340) arg1=0xffff888007f7c540
sh-142 [005] ..... 448.386458: vfs_read__exit: (ksys_read+0x75/0x100 <- vfs_read) arg1=0x1
sh-142 [005] ...1. 448.386469: vfs_read__entry: (vfs_read+0x4/0x340) arg1=0xffff888007f7c540
sh-142 [005] ..... 448.386476: vfs_read__exit: (ksys_read+0x75/0x100 <- vfs_read) arg1=0x1
sh-142 [005] ...1. 448.602073: vfs_read__entry: (vfs_read+0x4/0x340) arg1=0xffff888007f7c540
sh-142 [005] ..... 448.602089: vfs_read__exit: (ksys_read+0x75/0x100 <- vfs_read) arg1=0x1
Reported-by: kernel test robot <lkp@intel.com>
Link: https://lore.kernel.org/all/202302011530.7vm4O8Ro-lkp@intel.com/
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Add syntax error testcase and add-remove testcase for fprobe events. This ensures that the fprobe events can be added/removed and parser handles syntax errors correctly. Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Allow fprobe_events to trace raw tracepoints so that user can trace tracepoints which don't have traceevent wrappers. This new event is always available if the fprobe_events is enabled (thus no kconfig), because the fprobe_events depends on the trace-event and traceporint. e.g. # echo 't sched_overutilized_tp' >> dynamic_events # echo 't 9p_client_req' >> dynamic_events # cat dynamic_events t:tracepoints/sched_overutilized_tp sched_overutilized_tp t:tracepoints/_9p_client_req 9p_client_req The event name is based on the tracepoint name, but if it is started with digit character, an underscore '_' will be added. NOTE: to avoid further confusion, this renames TPARG_FL_TPOINT to TPARG_FL_TEVENT because this flag is used for eprobe (trace-event probe). And reuse TPARG_FL_TPOINT for this raw tracepoint probe. Reported-by: kernel test robot <lkp@intel.com> Link: https://lore.kernel.org/oe-kbuild-all/202305020453.afTJ3VVp-lkp@intel.com/ Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Move trace event parameter fetching code to common parser in trace_probe.c. This simplifies eprobe's trace-event variable fetching code by introducing a parse context data structure. Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Support function or tracepoint parameters by name if BTF support is enabled
and the event is for function entry (this feature can be used with kprobe-
events, fprobe-events and tracepoint probe events.)
Note that the BTF variable syntax does not require a prefix. If it starts
with an alphabetic character or an underscore ('_') without a prefix like
'$' and '%', it is considered as a BTF variable.
If you specify only the BTF variable name, the argument name will also
be the same name instead of 'arg*'.
# echo 'p vfs_read count pos' >> dynamic_events
# echo 'f vfs_write count pos' >> dynamic_events
# echo 't sched_overutilized_tp rd overutilized' >> dynamic_events
# cat dynamic_events
p:kprobes/p_vfs_read_0 vfs_read count=count pos=pos
f:fprobes/vfs_write__entry vfs_write count=count pos=pos
t:tracepoints/sched_overutilized_tp sched_overutilized_tp rd=rd overutilized=overutilized
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Reviewed-by: Alan Maguire <alan.maguire@oracle.com>
Tested-by: Alan Maguire <alan.maguire@oracle.com>
Add the '$arg*' meta fetch argument for function-entry probe events. This will be expanded to the all arguments of the function and the tracepoint using BTF function argument information. e.g. # echo 'p vfs_read $arg*' >> dynamic_events # echo 'f vfs_write $arg*' >> dynamic_events # echo 't sched_overutilized_tp $arg*' >> dynamic_events # cat dynamic_events p:kprobes/p_vfs_read_0 vfs_read file=file buf=buf count=count pos=pos f:fprobes/vfs_write__entry vfs_write file=file buf=buf count=count pos=pos t:tracepoints/sched_overutilized_tp sched_overutilized_tp rd=rd overutilized=overutilized Also, single '$arg[0-9]*' will be converted to the BTF function argument. NOTE: This seems like a wildcard, but a fake one at this moment. This is just for telling user that this can be expanded to several arguments. And it is not like other $-vars, you can not use this $arg* as a part of fetch args, e.g. specifying name "foo=$arg*" and using it in dereferences "+0($arg*)" will lead a parse error. Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Check the target function has non-void retval type and set the correct
fetch type if user doesn't specify it.
If the function returns void, $retval is rejected as below;
# echo 'f unregister_kprobes%return $retval' >> dynamic_events
sh: write error: No such file or directory
# cat error_log
[ 37.488397] trace_fprobe: error: This function returns 'void' type
Command: f unregister_kprobes%return $retval
^
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Add test cases for tracepoint probe events. Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Add test cases to check the BTF arguments correctly supported. Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Add a documentation about fprobe event tracing including tracepoint probe event and BTF argument. Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
|
Upstream branch: effcf62 |
|
At least one diff in series https://patchwork.kernel.org/project/netdevbpf/list/?series=748751 irrelevant now. Closing PR. |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Pull request for series with
subject: tracing: Add fprobe/tracepoint events
version: 12
url: https://patchwork.kernel.org/project/netdevbpf/list/?series=748751