riscv: Add KPROBES_ON_FTRACE supported
This patch adds support for kprobes on ftrace call sites to avoids much of the overhead with regular kprobes. Try it with simple steps: echo 'p:myprobe sys_clone a0=%a0 a1=%a1 stack_val=+4($stack)' > /sys/kernel/de bug/tracing/kprobe_events echo 1 > /sys/kernel/debug/tracing/events/kprobes/enable cat /sys/kernel/debug/tracing/trace tracer: nop entries-in-buffer/entries-written: 1/1 #P:1 _-----=> irqs-off / _----=> need-resched | / _---=> hardirq/softirq || / _--=> preempt-depth ||| / delay TASK-PID CPU# |||| TIMESTAMP FUNCTION | | | |||| | | sh-92 [000] .... 369.899962: myprobe: (sys_clone+0x0/0x28) a0=0x1200011 a1=0x0 stack_val=0x201c20ffffffe0 cat /sys/kernel/debug/kprobes/list ffffffe00020b584 k sys_clone+0x0 [FTRACE] ^^^^^^ Signed-off-by: Guo Ren <guoren@linux.alibaba.com> Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org> Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
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