ftrace: Fix DIRECT_CALLS to use SAVE_REGS by default
The commit 60c89718 ("ftrace: Make DIRECT_CALLS work WITH_ARGS and !WITH_REGS") changed DIRECT_CALLS to use SAVE_ARGS when there are multiple ftrace_ops at the same function, but since the x86 only support to jump to direct_call from ftrace_regs_caller, when we set the function tracer on the same target function on x86, ftrace-direct does not work as below (this actually works on arm64.) At first, insmod ftrace-direct.ko to put a direct_call on 'wake_up_process()'. # insmod kernel/samples/ftrace/ftrace-direct.ko # less trace ... <idle>-0 [006] ..s1. 564.686958: my_direct_func: waking up rcu_preempt-17 <idle>-0 [007] ..s1. 564.687836: my_direct_func: waking up kcompactd0-63 <idle>-0 [006] ..s1. 564.690926: my_direct_func: waking up rcu_preempt-17 <idle>-0 [006] ..s1. 564.696872: my_direct_func: waking up rcu_preempt-17 <idle>-0 [007] ..s1. 565.191982: my_direct_func: waking up kcompactd0-63 Setup a function filter to the 'wake_up_process' too, and enable it. # cd /sys/kernel/tracing/ # echo wake_up_process > set_ftrace_filter # echo function > current_tracer # less trace ... <idle>-0 [006] ..s3. 686.180972: wake_up_process <-call_timer_fn <idle>-0 [006] ..s3. 686.186919: wake_up_process <-call_timer_fn <idle>-0 [002] ..s3. 686.264049: wake_up_process <-call_timer_fn <idle>-0 [002] d.h6. 686.515216: wake_up_process <-kick_pool <idle>-0 [002] d.h6. 686.691386: wake_up_process <-kick_pool Then, only function tracer is shown on x86. But if you enable 'kprobe on ftrace' event (which uses SAVE_REGS flag) on the same function, it is shown again. # echo 'p wake_up_process' >> dynamic_events # echo 1 > events/kprobes/p_wake_up_process_0/enable # echo > trace # less trace ... <idle>-0 [006] ..s2. 2710.345919: p_wake_up_process_0: (wake_up_process+0x4/0x20) <idle>-0 [006] ..s3. 2710.345923: wake_up_process <-call_timer_fn <idle>-0 [006] ..s1. 2710.345928: my_direct_func: waking up rcu_preempt-17 <idle>-0 [006] ..s2. 2710.349931: p_wake_up_process_0: (wake_up_process+0x4/0x20) <idle>-0 [006] ..s3. 2710.349934: wake_up_process <-call_timer_fn <idle>-0 [006] ..s1. 2710.349937: my_direct_func: waking up rcu_preempt-17 To fix this issue, use SAVE_REGS flag for multiple ftrace_ops flag of direct_call by default. Link: https://lore.kernel.org/linux-trace-kernel/170484558617.178953.1590516949390270842.stgit@devnote2 Fixes: 60c89718 ("ftrace: Make DIRECT_CALLS work WITH_ARGS and !WITH_REGS") Cc: stable@vger.kernel.org Cc: Florent Revest <revest@chromium.org> Signed-off-by:Masami Hiramatsu (Google) <mhiramat@kernel.org> Reviewed-by:
Mark Rutland <mark.rutland@arm.com> Tested-by: Mark Rutland <mark.rutland@arm.com> [arm64] Acked-by:
Jiri Olsa <jolsa@kernel.org> Signed-off-by:
Steven Rostedt (Google) <rostedt@goodmis.org>
parent
ca185770
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